refactor: memo filter

plugin/filter/common_converter.go

@@ -0,0 +1,448 @@
+package filter
+
+import (
+	"fmt"
+	"slices"
+	"strings"
+
+	"github.com/pkg/errors"
+	exprv1 "google.golang.org/genproto/googleapis/api/expr/v1alpha1"
+)
+
+// CommonSQLConverter handles the common CEL to SQL conversion logic
+type CommonSQLConverter struct {
+	dialect    SQLDialect
+	paramIndex int
+}
+
+// NewCommonSQLConverter creates a new converter with the specified dialect
+func NewCommonSQLConverter(dialect SQLDialect) *CommonSQLConverter {
+	return &CommonSQLConverter{
+		dialect:    dialect,
+		paramIndex: 1,
+	}
+}
+
+// ConvertExprToSQL converts a CEL expression to SQL using the configured dialect
+func (c *CommonSQLConverter) ConvertExprToSQL(ctx *ConvertContext, expr *exprv1.Expr) error {
+	if v, ok := expr.ExprKind.(*exprv1.Expr_CallExpr); ok {
+		switch v.CallExpr.Function {
+		case "_||_", "_&&_":
+			return c.handleLogicalOperator(ctx, v.CallExpr)
+		case "!_":
+			return c.handleNotOperator(ctx, v.CallExpr)
+		case "_==_", "_!=_", "_<_", "_>_", "_<=_", "_>=_":
+			return c.handleComparisonOperator(ctx, v.CallExpr)
+		case "@in":
+			return c.handleInOperator(ctx, v.CallExpr)
+		case "contains":
+			return c.handleContainsOperator(ctx, v.CallExpr)
+		}
+	} else if v, ok := expr.ExprKind.(*exprv1.Expr_IdentExpr); ok {
+		return c.handleIdentifier(ctx, v.IdentExpr)
+	}
+	return nil
+}
+
+func (c *CommonSQLConverter) handleLogicalOperator(ctx *ConvertContext, callExpr *exprv1.Expr_Call) error {
+	if len(callExpr.Args) != 2 {
+		return errors.Errorf("invalid number of arguments for %s", callExpr.Function)
+	}
+
+	if _, err := ctx.Buffer.WriteString("("); err != nil {
+		return err
+	}
+
+	if err := c.ConvertExprToSQL(ctx, callExpr.Args[0]); err != nil {
+		return err
+	}
+
+	operator := "AND"
+	if callExpr.Function == "_||_" {
+		operator = "OR"
+	}
+
+	if _, err := ctx.Buffer.WriteString(fmt.Sprintf(" %s ", operator)); err != nil {
+		return err
+	}
+
+	if err := c.ConvertExprToSQL(ctx, callExpr.Args[1]); err != nil {
+		return err
+	}
+
+	if _, err := ctx.Buffer.WriteString(")"); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (c *CommonSQLConverter) handleNotOperator(ctx *ConvertContext, callExpr *exprv1.Expr_Call) error {
+	if len(callExpr.Args) != 1 {
+		return errors.Errorf("invalid number of arguments for %s", callExpr.Function)
+	}
+
+	if _, err := ctx.Buffer.WriteString("NOT ("); err != nil {
+		return err
+	}
+
+	if err := c.ConvertExprToSQL(ctx, callExpr.Args[0]); err != nil {
+		return err
+	}
+
+	if _, err := ctx.Buffer.WriteString(")"); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (c *CommonSQLConverter) handleComparisonOperator(ctx *ConvertContext, callExpr *exprv1.Expr_Call) error {
+	if len(callExpr.Args) != 2 {
+		return errors.Errorf("invalid number of arguments for %s", callExpr.Function)
+	}
+
+	// Check if the left side is a function call like size(tags)
+	if leftCallExpr, ok := callExpr.Args[0].ExprKind.(*exprv1.Expr_CallExpr); ok {
+		if leftCallExpr.CallExpr.Function == "size" {
+			return c.handleSizeComparison(ctx, callExpr, leftCallExpr.CallExpr)
+		}
+	}
+
+	identifier, err := GetIdentExprName(callExpr.Args[0])
+	if err != nil {
+		return err
+	}
+
+	if !slices.Contains([]string{"creator_id", "created_ts", "updated_ts", "visibility", "content", "has_task_list"}, identifier) {
+		return errors.Errorf("invalid identifier for %s", callExpr.Function)
+	}
+
+	value, err := GetExprValue(callExpr.Args[1])
+	if err != nil {
+		return err
+	}
+
+	operator := c.getComparisonOperator(callExpr.Function)
+
+	switch identifier {
+	case "created_ts", "updated_ts":
+		return c.handleTimestampComparison(ctx, identifier, operator, value)
+	case "visibility", "content":
+		return c.handleStringComparison(ctx, identifier, operator, value)
+	case "creator_id":
+		return c.handleIntComparison(ctx, identifier, operator, value)
+	case "has_task_list":
+		return c.handleBooleanComparison(ctx, identifier, operator, value)
+	}
+
+	return nil
+}
+
+func (c *CommonSQLConverter) handleSizeComparison(ctx *ConvertContext, callExpr *exprv1.Expr_Call, sizeCall *exprv1.Expr_Call) error {
+	if len(sizeCall.Args) != 1 {
+		return errors.New("size function requires exactly one argument")
+	}
+
+	identifier, err := GetIdentExprName(sizeCall.Args[0])
+	if err != nil {
+		return err
+	}
+
+	if identifier != "tags" {
+		return errors.Errorf("size function only supports 'tags' identifier, got: %s", identifier)
+	}
+
+	value, err := GetExprValue(callExpr.Args[1])
+	if err != nil {
+		return err
+	}
+
+	valueInt, ok := value.(int64)
+	if !ok {
+		return errors.New("size comparison value must be an integer")
+	}
+
+	operator := c.getComparisonOperator(callExpr.Function)
+
+	if _, err := ctx.Buffer.WriteString(fmt.Sprintf("%s %s %s",
+		c.dialect.GetJSONArrayLength("$.tags"),
+		operator,
+		c.dialect.GetParameterPlaceholder(c.paramIndex))); err != nil {
+		return err
+	}
+
+	ctx.Args = append(ctx.Args, valueInt)
+	c.paramIndex++
+
+	return nil
+}
+
+func (c *CommonSQLConverter) handleInOperator(ctx *ConvertContext, callExpr *exprv1.Expr_Call) error {
+	if len(callExpr.Args) != 2 {
+		return errors.Errorf("invalid number of arguments for %s", callExpr.Function)
+	}
+
+	// Check if this is "element in collection" syntax
+	if identifier, err := GetIdentExprName(callExpr.Args[1]); err == nil {
+		if identifier == "tags" {
+			return c.handleElementInTags(ctx, callExpr.Args[0])
+		}
+		return errors.Errorf("invalid collection identifier for %s: %s", callExpr.Function, identifier)
+	}
+
+	// Original logic for "identifier in [list]" syntax
+	identifier, err := GetIdentExprName(callExpr.Args[0])
+	if err != nil {
+		return err
+	}
+
+	if !slices.Contains([]string{"tag", "visibility"}, identifier) {
+		return errors.Errorf("invalid identifier for %s", callExpr.Function)
+	}
+
+	values := []any{}
+	for _, element := range callExpr.Args[1].GetListExpr().Elements {
+		value, err := GetConstValue(element)
+		if err != nil {
+			return err
+		}
+		values = append(values, value)
+	}
+
+	if identifier == "tag" {
+		return c.handleTagInList(ctx, values)
+	} else if identifier == "visibility" {
+		return c.handleVisibilityInList(ctx, values)
+	}
+
+	return nil
+}
+
+func (c *CommonSQLConverter) handleElementInTags(ctx *ConvertContext, elementExpr *exprv1.Expr) error {
+	element, err := GetConstValue(elementExpr)
+	if err != nil {
+		return errors.Errorf("first argument must be a constant value for 'element in tags': %v", err)
+	}
+
+	// Use dialect-specific JSON contains logic
+	sqlExpr := c.dialect.GetJSONContains("$.tags", "element")
+	if _, err := ctx.Buffer.WriteString(sqlExpr); err != nil {
+		return err
+	}
+
+	// For SQLite, we need a different approach since it uses LIKE
+	if _, ok := c.dialect.(*SQLiteDialect); ok {
+		ctx.Args = append(ctx.Args, fmt.Sprintf(`%%"%s"%%`, element))
+	} else {
+		ctx.Args = append(ctx.Args, element)
+	}
+	c.paramIndex++
+
+	return nil
+}
+
+func (c *CommonSQLConverter) handleTagInList(ctx *ConvertContext, values []any) error {
+	subconditions := []string{}
+	args := []any{}
+
+	for _, v := range values {
+		if _, ok := c.dialect.(*SQLiteDialect); ok {
+			subconditions = append(subconditions, c.dialect.GetJSONLike("$.tags", "pattern"))
+			args = append(args, fmt.Sprintf(`%%"%s"%%`, v))
+		} else {
+			subconditions = append(subconditions, c.dialect.GetJSONContains("$.tags", "element"))
+			args = append(args, v)
+		}
+		c.paramIndex++
+	}
+
+	if len(subconditions) == 1 {
+		if _, err := ctx.Buffer.WriteString(subconditions[0]); err != nil {
+			return err
+		}
+	} else {
+		if _, err := ctx.Buffer.WriteString(fmt.Sprintf("(%s)", strings.Join(subconditions, " OR "))); err != nil {
+			return err
+		}
+	}
+
+	ctx.Args = append(ctx.Args, args...)
+	return nil
+}
+
+func (c *CommonSQLConverter) handleVisibilityInList(ctx *ConvertContext, values []any) error {
+	placeholders := []string{}
+	for range values {
+		placeholders = append(placeholders, c.dialect.GetParameterPlaceholder(c.paramIndex))
+		c.paramIndex++
+	}
+
+	tablePrefix := c.dialect.GetTablePrefix()
+	if _, err := ctx.Buffer.WriteString(fmt.Sprintf("%s.`visibility` IN (%s)", tablePrefix, strings.Join(placeholders, ","))); err != nil {
+		return err
+	}
+
+	ctx.Args = append(ctx.Args, values...)
+	return nil
+}
+
+func (c *CommonSQLConverter) handleContainsOperator(ctx *ConvertContext, callExpr *exprv1.Expr_Call) error {
+	if len(callExpr.Args) != 1 {
+		return errors.Errorf("invalid number of arguments for %s", callExpr.Function)
+	}
+
+	identifier, err := GetIdentExprName(callExpr.Target)
+	if err != nil {
+		return err
+	}
+
+	if identifier != "content" {
+		return errors.Errorf("invalid identifier for %s", callExpr.Function)
+	}
+
+	arg, err := GetConstValue(callExpr.Args[0])
+	if err != nil {
+		return err
+	}
+
+	tablePrefix := c.dialect.GetTablePrefix()
+	if _, err := ctx.Buffer.WriteString(fmt.Sprintf("%s.`content` LIKE %s", tablePrefix, c.dialect.GetParameterPlaceholder(c.paramIndex))); err != nil {
+		return err
+	}
+
+	ctx.Args = append(ctx.Args, fmt.Sprintf("%%%s%%", arg))
+	c.paramIndex++
+
+	return nil
+}
+
+func (c *CommonSQLConverter) handleIdentifier(ctx *ConvertContext, identExpr *exprv1.Expr_Ident) error {
+	identifier := identExpr.GetName()
+
+	if !slices.Contains([]string{"pinned", "has_task_list"}, identifier) {
+		return errors.Errorf("invalid identifier %s", identifier)
+	}
+
+	if identifier == "pinned" {
+		tablePrefix := c.dialect.GetTablePrefix()
+		if _, err := ctx.Buffer.WriteString(fmt.Sprintf("%s.`pinned` IS TRUE", tablePrefix)); err != nil {
+			return err
+		}
+	} else if identifier == "has_task_list" {
+		if _, err := ctx.Buffer.WriteString(c.dialect.GetBooleanCheck("$.property.hasTaskList")); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func (c *CommonSQLConverter) handleTimestampComparison(ctx *ConvertContext, field, operator string, value interface{}) error {
+	valueInt, ok := value.(int64)
+	if !ok {
+		return errors.New("invalid integer timestamp value")
+	}
+
+	timestampField := c.dialect.GetTimestampComparison(field)
+	if _, err := ctx.Buffer.WriteString(fmt.Sprintf("%s %s %s", timestampField, operator, c.dialect.GetParameterPlaceholder(c.paramIndex))); err != nil {
+		return err
+	}
+
+	ctx.Args = append(ctx.Args, valueInt)
+	c.paramIndex++
+
+	return nil
+}
+
+func (c *CommonSQLConverter) handleStringComparison(ctx *ConvertContext, field, operator string, value interface{}) error {
+	if operator != "=" && operator != "!=" {
+		return errors.Errorf("invalid operator for %s", field)
+	}
+
+	valueStr, ok := value.(string)
+	if !ok {
+		return errors.New("invalid string value")
+	}
+
+	tablePrefix := c.dialect.GetTablePrefix()
+	fieldName := field
+	if field == "visibility" {
+		fieldName = "`visibility`"
+	} else if field == "content" {
+		fieldName = "`content`"
+	}
+
+	if _, err := ctx.Buffer.WriteString(fmt.Sprintf("%s.%s %s %s", tablePrefix, fieldName, operator, c.dialect.GetParameterPlaceholder(c.paramIndex))); err != nil {
+		return err
+	}
+
+	ctx.Args = append(ctx.Args, valueStr)
+	c.paramIndex++
+
+	return nil
+}
+
+func (c *CommonSQLConverter) handleIntComparison(ctx *ConvertContext, field, operator string, value interface{}) error {
+	if operator != "=" && operator != "!=" {
+		return errors.Errorf("invalid operator for %s", field)
+	}
+
+	valueInt, ok := value.(int64)
+	if !ok {
+		return errors.New("invalid int value")
+	}
+
+	tablePrefix := c.dialect.GetTablePrefix()
+	if _, err := ctx.Buffer.WriteString(fmt.Sprintf("%s.`%s` %s %s", tablePrefix, field, operator, c.dialect.GetParameterPlaceholder(c.paramIndex))); err != nil {
+		return err
+	}
+
+	ctx.Args = append(ctx.Args, valueInt)
+	c.paramIndex++
+
+	return nil
+}
+
+func (c *CommonSQLConverter) handleBooleanComparison(ctx *ConvertContext, field, operator string, value interface{}) error {
+	if operator != "=" && operator != "!=" {
+		return errors.Errorf("invalid operator for %s", field)
+	}
+
+	valueBool, ok := value.(bool)
+	if !ok {
+		return errors.New("invalid boolean value for has_task_list")
+	}
+
+	sqlExpr := c.dialect.GetBooleanComparison("$.property.hasTaskList", valueBool)
+	if _, err := ctx.Buffer.WriteString(sqlExpr); err != nil {
+		return err
+	}
+
+	// For dialects that need parameters (PostgreSQL)
+	if _, ok := c.dialect.(*PostgreSQLDialect); ok {
+		ctx.Args = append(ctx.Args, valueBool)
+		c.paramIndex++
+	}
+
+	return nil
+}
+
+func (c *CommonSQLConverter) getComparisonOperator(function string) string {
+	switch function {
+	case "_==_":
+		return "="
+	case "_!=_":
+		return "!="
+	case "_<_":
+		return "<"
+	case "_>_":
+		return ">"
+	case "_<=_":
+		return "<="
+	case "_>=_":
+		return ">="
+	default:
+		return "="
+	}
+}

plugin/filter/dialect.go

@@ -0,0 +1,212 @@
+package filter
+
+import (
+	"fmt"
+	"strings"
+)
+
+// SQLDialect defines database-specific SQL generation methods
+type SQLDialect interface {
+	// Basic field access
+	GetTablePrefix() string
+	GetParameterPlaceholder(index int) string
+
+	// JSON operations
+	GetJSONExtract(path string) string
+	GetJSONArrayLength(path string) string
+	GetJSONContains(path, element string) string
+	GetJSONLike(path, pattern string) string
+
+	// Boolean operations
+	GetBooleanValue(value bool) interface{}
+	GetBooleanComparison(path string, value bool) string
+	GetBooleanCheck(path string) string
+
+	// Timestamp operations
+	GetTimestampComparison(field string) string
+	GetCurrentTimestamp() string
+}
+
+// DatabaseType represents the type of database
+type DatabaseType string
+
+const (
+	SQLite     DatabaseType = "sqlite"
+	MySQL      DatabaseType = "mysql"
+	PostgreSQL DatabaseType = "postgres"
+)
+
+// GetDialect returns the appropriate dialect for the database type
+func GetDialect(dbType DatabaseType) SQLDialect {
+	switch dbType {
+	case SQLite:
+		return &SQLiteDialect{}
+	case MySQL:
+		return &MySQLDialect{}
+	case PostgreSQL:
+		return &PostgreSQLDialect{}
+	default:
+		return &SQLiteDialect{} // default fallback
+	}
+}
+
+// SQLiteDialect implements SQLDialect for SQLite
+type SQLiteDialect struct{}
+
+func (d *SQLiteDialect) GetTablePrefix() string {
+	return "`memo`"
+}
+
+func (d *SQLiteDialect) GetParameterPlaceholder(index int) string {
+	return "?"
+}
+
+func (d *SQLiteDialect) GetJSONExtract(path string) string {
+	return fmt.Sprintf("JSON_EXTRACT(%s.`payload`, '%s')", d.GetTablePrefix(), path)
+}
+
+func (d *SQLiteDialect) GetJSONArrayLength(path string) string {
+	return fmt.Sprintf("JSON_ARRAY_LENGTH(COALESCE(%s, JSON_ARRAY()))", d.GetJSONExtract(path))
+}
+
+func (d *SQLiteDialect) GetJSONContains(path, element string) string {
+	return fmt.Sprintf("%s LIKE ?", d.GetJSONExtract(path))
+}
+
+func (d *SQLiteDialect) GetJSONLike(path, pattern string) string {
+	return fmt.Sprintf("%s LIKE ?", d.GetJSONExtract(path))
+}
+
+func (d *SQLiteDialect) GetBooleanValue(value bool) interface{} {
+	if value {
+		return 1
+	}
+	return 0
+}
+
+func (d *SQLiteDialect) GetBooleanComparison(path string, value bool) string {
+	return fmt.Sprintf("%s = %d", d.GetJSONExtract(path), d.GetBooleanValue(value))
+}
+
+func (d *SQLiteDialect) GetBooleanCheck(path string) string {
+	return fmt.Sprintf("%s IS TRUE", d.GetJSONExtract(path))
+}
+
+func (d *SQLiteDialect) GetTimestampComparison(field string) string {
+	return fmt.Sprintf("%s.`%s`", d.GetTablePrefix(), field)
+}
+
+func (d *SQLiteDialect) GetCurrentTimestamp() string {
+	return "strftime('%s', 'now')"
+}
+
+// MySQLDialect implements SQLDialect for MySQL
+type MySQLDialect struct{}
+
+func (d *MySQLDialect) GetTablePrefix() string {
+	return "`memo`"
+}
+
+func (d *MySQLDialect) GetParameterPlaceholder(index int) string {
+	return "?"
+}
+
+func (d *MySQLDialect) GetJSONExtract(path string) string {
+	return fmt.Sprintf("JSON_EXTRACT(%s.`payload`, '%s')", d.GetTablePrefix(), path)
+}
+
+func (d *MySQLDialect) GetJSONArrayLength(path string) string {
+	return fmt.Sprintf("JSON_LENGTH(COALESCE(%s, JSON_ARRAY()))", d.GetJSONExtract(path))
+}
+
+func (d *MySQLDialect) GetJSONContains(path, element string) string {
+	return fmt.Sprintf("JSON_CONTAINS(%s, ?)", d.GetJSONExtract(path))
+}
+
+func (d *MySQLDialect) GetJSONLike(path, pattern string) string {
+	return fmt.Sprintf("%s LIKE ?", d.GetJSONExtract(path))
+}
+
+func (d *MySQLDialect) GetBooleanValue(value bool) interface{} {
+	return value
+}
+
+func (d *MySQLDialect) GetBooleanComparison(path string, value bool) string {
+	boolStr := "false"
+	if value {
+		boolStr = "true"
+	}
+	return fmt.Sprintf("%s = CAST('%s' AS JSON)", d.GetJSONExtract(path), boolStr)
+}
+
+func (d *MySQLDialect) GetBooleanCheck(path string) string {
+	return fmt.Sprintf("%s = CAST('true' AS JSON)", d.GetJSONExtract(path))
+}
+
+func (d *MySQLDialect) GetTimestampComparison(field string) string {
+	return fmt.Sprintf("UNIX_TIMESTAMP(%s.`%s`)", d.GetTablePrefix(), field)
+}
+
+func (d *MySQLDialect) GetCurrentTimestamp() string {
+	return "UNIX_TIMESTAMP()"
+}
+
+// PostgreSQLDialect implements SQLDialect for PostgreSQL
+type PostgreSQLDialect struct{}
+
+func (d *PostgreSQLDialect) GetTablePrefix() string {
+	return "memo"
+}
+
+func (d *PostgreSQLDialect) GetParameterPlaceholder(index int) string {
+	return fmt.Sprintf("$%d", index)
+}
+
+func (d *PostgreSQLDialect) GetJSONExtract(path string) string {
+	// Convert $.property.hasTaskList to payload->'property'->>'hasTaskList'
+	parts := strings.Split(strings.TrimPrefix(path, "$."), ".")
+	result := fmt.Sprintf("%s.payload", d.GetTablePrefix())
+	for i, part := range parts {
+		if i == len(parts)-1 {
+			result += fmt.Sprintf("->>'%s'", part)
+		} else {
+			result += fmt.Sprintf("->'%s'", part)
+		}
+	}
+	return result
+}
+
+func (d *PostgreSQLDialect) GetJSONArrayLength(path string) string {
+	jsonPath := strings.Replace(path, "$.tags", "payload->'tags'", 1)
+	return fmt.Sprintf("jsonb_array_length(COALESCE(%s.%s, '[]'::jsonb))", d.GetTablePrefix(), jsonPath)
+}
+
+func (d *PostgreSQLDialect) GetJSONContains(path, element string) string {
+	jsonPath := strings.Replace(path, "$.tags", "payload->'tags'", 1)
+	return fmt.Sprintf("%s.%s @> jsonb_build_array(?)", d.GetTablePrefix(), jsonPath)
+}
+
+func (d *PostgreSQLDialect) GetJSONLike(path, pattern string) string {
+	jsonPath := strings.Replace(path, "$.tags", "payload->'tags'", 1)
+	return fmt.Sprintf("%s.%s @> jsonb_build_array(?)", d.GetTablePrefix(), jsonPath)
+}
+
+func (d *PostgreSQLDialect) GetBooleanValue(value bool) interface{} {
+	return value
+}
+
+func (d *PostgreSQLDialect) GetBooleanComparison(path string, value bool) string {
+	return fmt.Sprintf("(%s)::boolean = ?", d.GetJSONExtract(path))
+}
+
+func (d *PostgreSQLDialect) GetBooleanCheck(path string) string {
+	return fmt.Sprintf("(%s)::boolean IS TRUE", d.GetJSONExtract(path))
+}
+
+func (d *PostgreSQLDialect) GetTimestampComparison(field string) string {
+	return fmt.Sprintf("EXTRACT(EPOCH FROM %s.%s)", d.GetTablePrefix(), field)
+}
+
+func (d *PostgreSQLDialect) GetCurrentTimestamp() string {
+	return "EXTRACT(EPOCH FROM NOW())"
+}

plugin/filter/filter.go

@@ -18,6 +18,7 @@ var MemoFilterCELAttributes = []cel.EnvOption{
 	cel.Variable("updated_ts", cel.IntType),
 	cel.Variable("pinned", cel.BoolType),
 	cel.Variable("tag", cel.StringType),
+	cel.Variable("tags", cel.ListType(cel.StringType)),
 	cel.Variable("visibility", cel.StringType),
 	cel.Variable("has_task_list", cel.BoolType),
 	// Current timestamp function.

plugin/filter/templates.go

@@ -0,0 +1,146 @@
+package filter
+
+import (
+	"fmt"
+)
+
+// SQLTemplate holds database-specific SQL fragments
+type SQLTemplate struct {
+	SQLite     string
+	MySQL      string
+	PostgreSQL string
+}
+
+// TemplateDBType represents the database type for templates
+type TemplateDBType string
+
+const (
+	SQLiteTemplate     TemplateDBType = "sqlite"
+	MySQLTemplate      TemplateDBType = "mysql"
+	PostgreSQLTemplate TemplateDBType = "postgres"
+)
+
+// SQLTemplates contains common SQL patterns for different databases
+var SQLTemplates = map[string]SQLTemplate{
+	"json_extract": {
+		SQLite:     "JSON_EXTRACT(`memo`.`payload`, '%s')",
+		MySQL:      "JSON_EXTRACT(`memo`.`payload`, '%s')",
+		PostgreSQL: "memo.payload%s",
+	},
+	"json_array_length": {
+		SQLite:     "JSON_ARRAY_LENGTH(COALESCE(JSON_EXTRACT(`memo`.`payload`, '$.tags'), JSON_ARRAY()))",
+		MySQL:      "JSON_LENGTH(COALESCE(JSON_EXTRACT(`memo`.`payload`, '$.tags'), JSON_ARRAY()))",
+		PostgreSQL: "jsonb_array_length(COALESCE(memo.payload->'tags', '[]'::jsonb))",
+	},
+	"json_contains_element": {
+		SQLite:     "JSON_EXTRACT(`memo`.`payload`, '$.tags') LIKE ?",
+		MySQL:      "JSON_CONTAINS(JSON_EXTRACT(`memo`.`payload`, '$.tags'), ?)",
+		PostgreSQL: "memo.payload->'tags' @> jsonb_build_array(?)",
+	},
+	"json_contains_tag": {
+		SQLite:     "JSON_EXTRACT(`memo`.`payload`, '$.tags') LIKE ?",
+		MySQL:      "JSON_CONTAINS(JSON_EXTRACT(`memo`.`payload`, '$.tags'), ?)",
+		PostgreSQL: "memo.payload->'tags' @> jsonb_build_array(?)",
+	},
+	"boolean_true": {
+		SQLite:     "JSON_EXTRACT(`memo`.`payload`, '$.property.hasTaskList') = 1",
+		MySQL:      "JSON_EXTRACT(`memo`.`payload`, '$.property.hasTaskList') = CAST('true' AS JSON)",
+		PostgreSQL: "(memo.payload->'property'->>'hasTaskList')::boolean = true",
+	},
+	"boolean_false": {
+		SQLite:     "JSON_EXTRACT(`memo`.`payload`, '$.property.hasTaskList') = 0",
+		MySQL:      "JSON_EXTRACT(`memo`.`payload`, '$.property.hasTaskList') = CAST('false' AS JSON)",
+		PostgreSQL: "(memo.payload->'property'->>'hasTaskList')::boolean = false",
+	},
+	"boolean_not_true": {
+		SQLite:     "JSON_EXTRACT(`memo`.`payload`, '$.property.hasTaskList') != 1",
+		MySQL:      "JSON_EXTRACT(`memo`.`payload`, '$.property.hasTaskList') != CAST('true' AS JSON)",
+		PostgreSQL: "(memo.payload->'property'->>'hasTaskList')::boolean != true",
+	},
+	"boolean_not_false": {
+		SQLite:     "JSON_EXTRACT(`memo`.`payload`, '$.property.hasTaskList') != 0",
+		MySQL:      "JSON_EXTRACT(`memo`.`payload`, '$.property.hasTaskList') != CAST('false' AS JSON)",
+		PostgreSQL: "(memo.payload->'property'->>'hasTaskList')::boolean != false",
+	},
+	"boolean_compare": {
+		SQLite:     "JSON_EXTRACT(`memo`.`payload`, '$.property.hasTaskList') %s ?",
+		MySQL:      "JSON_EXTRACT(`memo`.`payload`, '$.property.hasTaskList') %s CAST(? AS JSON)",
+		PostgreSQL: "(memo.payload->'property'->>'hasTaskList')::boolean %s ?",
+	},
+	"boolean_check": {
+		SQLite:     "JSON_EXTRACT(`memo`.`payload`, '$.property.hasTaskList') IS TRUE",
+		MySQL:      "JSON_EXTRACT(`memo`.`payload`, '$.property.hasTaskList') = CAST('true' AS JSON)",
+		PostgreSQL: "(memo.payload->'property'->>'hasTaskList')::boolean IS TRUE",
+	},
+	"table_prefix": {
+		SQLite:     "`memo`",
+		MySQL:      "`memo`",
+		PostgreSQL: "memo",
+	},
+	"timestamp_field": {
+		SQLite:     "`memo`.`%s`",
+		MySQL:      "UNIX_TIMESTAMP(`memo`.`%s`)",
+		PostgreSQL: "EXTRACT(EPOCH FROM memo.%s)",
+	},
+	"content_like": {
+		SQLite:     "`memo`.`content` LIKE ?",
+		MySQL:      "`memo`.`content` LIKE ?",
+		PostgreSQL: "memo.content ILIKE ?",
+	},
+	"visibility_in": {
+		SQLite:     "`memo`.`visibility` IN (%s)",
+		MySQL:      "`memo`.`visibility` IN (%s)",
+		PostgreSQL: "memo.visibility IN (%s)",
+	},
+}
+
+// GetSQL returns the appropriate SQL for the given template and database type
+func GetSQL(templateName string, dbType TemplateDBType) string {
+	template, exists := SQLTemplates[templateName]
+	if !exists {
+		return ""
+	}
+
+	switch dbType {
+	case SQLiteTemplate:
+		return template.SQLite
+	case MySQLTemplate:
+		return template.MySQL
+	case PostgreSQLTemplate:
+		return template.PostgreSQL
+	default:
+		return template.SQLite
+	}
+}
+
+// GetParameterPlaceholder returns the appropriate parameter placeholder for the database
+func GetParameterPlaceholder(dbType TemplateDBType, index int) string {
+	switch dbType {
+	case PostgreSQLTemplate:
+		return fmt.Sprintf("$%d", index)
+	default:
+		return "?"
+	}
+}
+
+// GetParameterValue returns the appropriate parameter value for the database
+func GetParameterValue(dbType TemplateDBType, templateName string, value interface{}) interface{} {
+	switch templateName {
+	case "json_contains_element", "json_contains_tag":
+		if dbType == SQLiteTemplate {
+			return fmt.Sprintf(`%%"%s"%%`, value)
+		}
+		return value
+	default:
+		return value
+	}
+}
+
+// FormatPlaceholders formats a list of placeholders for the given database type
+func FormatPlaceholders(dbType TemplateDBType, count int, startIndex int) []string {
+	placeholders := make([]string, count)
+	for i := 0; i < count; i++ {
+		placeholders[i] = GetParameterPlaceholder(dbType, startIndex+i)
+	}
+	return placeholders
+}

store/db/mysql/memo_filter.go

@@ -12,6 +12,12 @@ import (
 )
 
 func (d *DB) ConvertExprToSQL(ctx *filter.ConvertContext, expr *exprv1.Expr) error {
+	return d.convertWithTemplates(ctx, expr)
+}
+
+func (d *DB) convertWithTemplates(ctx *filter.ConvertContext, expr *exprv1.Expr) error {
+	const dbType = filter.MySQLTemplate
+
 	if v, ok := expr.ExprKind.(*exprv1.Expr_CallExpr); ok {
 		switch v.CallExpr.Function {
 		case "_||_", "_&&_":
@@ -21,7 +27,7 @@ func (d *DB) ConvertExprToSQL(ctx *filter.ConvertContext, expr *exprv1.Expr) err
 			if _, err := ctx.Buffer.WriteString("("); err != nil {
 				return err
 			}
-			if err := d.ConvertExprToSQL(ctx, v.CallExpr.Args[0]); err != nil {
+			if err := d.convertWithTemplates(ctx, v.CallExpr.Args[0]); err != nil {
 				return err
 			}
 			operator := "AND"
@@ -31,7 +37,7 @@ func (d *DB) ConvertExprToSQL(ctx *filter.ConvertContext, expr *exprv1.Expr) err
 			if _, err := ctx.Buffer.WriteString(fmt.Sprintf(" %s ", operator)); err != nil {
 				return err
 			}
-			if err := d.ConvertExprToSQL(ctx, v.CallExpr.Args[1]); err != nil {
+			if err := d.convertWithTemplates(ctx, v.CallExpr.Args[1]); err != nil {
 				return err
 			}
 			if _, err := ctx.Buffer.WriteString(")"); err != nil {
@@ -44,7 +50,7 @@ func (d *DB) ConvertExprToSQL(ctx *filter.ConvertContext, expr *exprv1.Expr) err
 			if _, err := ctx.Buffer.WriteString("NOT ("); err != nil {
 				return err
 			}
-			if err := d.ConvertExprToSQL(ctx, v.CallExpr.Args[0]); err != nil {
+			if err := d.convertWithTemplates(ctx, v.CallExpr.Args[0]); err != nil {
 				return err
 			}
 			if _, err := ctx.Buffer.WriteString(")"); err != nil {
@@ -54,6 +60,39 @@ func (d *DB) ConvertExprToSQL(ctx *filter.ConvertContext, expr *exprv1.Expr) err
 			if len(v.CallExpr.Args) != 2 {
 				return errors.Errorf("invalid number of arguments for %s", v.CallExpr.Function)
 			}
+			// Check if the left side is a function call like size(tags)
+			if leftCallExpr, ok := v.CallExpr.Args[0].ExprKind.(*exprv1.Expr_CallExpr); ok {
+				if leftCallExpr.CallExpr.Function == "size" {
+					// Handle size(tags) comparison
+					if len(leftCallExpr.CallExpr.Args) != 1 {
+						return errors.New("size function requires exactly one argument")
+					}
+					identifier, err := filter.GetIdentExprName(leftCallExpr.CallExpr.Args[0])
+					if err != nil {
+						return err
+					}
+					if identifier != "tags" {
+						return errors.Errorf("size function only supports 'tags' identifier, got: %s", identifier)
+					}
+					value, err := filter.GetExprValue(v.CallExpr.Args[1])
+					if err != nil {
+						return err
+					}
+					valueInt, ok := value.(int64)
+					if !ok {
+						return errors.New("size comparison value must be an integer")
+					}
+					operator := d.getComparisonOperator(v.CallExpr.Function)
+
+					if _, err := ctx.Buffer.WriteString(fmt.Sprintf("%s %s ?",
+						filter.GetSQL("json_array_length", dbType), operator)); err != nil {
+						return err
+					}
+					ctx.Args = append(ctx.Args, valueInt)
+					return nil
+				}
+			}
+
 			identifier, err := filter.GetIdentExprName(v.CallExpr.Args[0])
 			if err != nil {
 				return err
@@ -65,38 +104,19 @@ func (d *DB) ConvertExprToSQL(ctx *filter.ConvertContext, expr *exprv1.Expr) err
 			if err != nil {
 				return err
 			}
-			operator := "="
-			switch v.CallExpr.Function {
-			case "_==_":
-				operator = "="
-			case "_!=_":
-				operator = "!="
-			case "_<_":
-				operator = "<"
-			case "_>_":
-				operator = ">"
-			case "_<=_":
-				operator = "<="
-			case "_>=_":
-				operator = ">="
-			}
+			operator := d.getComparisonOperator(v.CallExpr.Function)
 
 			if identifier == "created_ts" || identifier == "updated_ts" {
-				timestampInt, ok := value.(int64)
+				valueInt, ok := value.(int64)
 				if !ok {
-					return errors.New("invalid timestamp value")
+					return errors.New("invalid integer timestamp value")
 				}
 
-				var factor string
-				if identifier == "created_ts" {
-					factor = "UNIX_TIMESTAMP(`memo`.`created_ts`)"
-				} else if identifier == "updated_ts" {
-					factor = "UNIX_TIMESTAMP(`memo`.`updated_ts`)"
-				}
-				if _, err := ctx.Buffer.WriteString(fmt.Sprintf("%s %s ?", factor, operator)); err != nil {
+				timestampSQL := fmt.Sprintf(filter.GetSQL("timestamp_field", dbType), identifier)
+				if _, err := ctx.Buffer.WriteString(fmt.Sprintf("%s %s ?", timestampSQL, operator)); err != nil {
 					return err
 				}
-				ctx.Args = append(ctx.Args, timestampInt)
+				ctx.Args = append(ctx.Args, valueInt)
 			} else if identifier == "visibility" || identifier == "content" {
 				if operator != "=" && operator != "!=" {
 					return errors.Errorf("invalid operator for %s", v.CallExpr.Function)
@@ -106,13 +126,13 @@ func (d *DB) ConvertExprToSQL(ctx *filter.ConvertContext, expr *exprv1.Expr) err
 					return errors.New("invalid string value")
 				}
 
-				var factor string
+				var sqlTemplate string
 				if identifier == "visibility" {
-					factor = "`memo`.`visibility`"
+					sqlTemplate = filter.GetSQL("table_prefix", dbType) + ".`visibility`"
 				} else if identifier == "content" {
-					factor = "`memo`.`content`"
+					sqlTemplate = filter.GetSQL("table_prefix", dbType) + ".`content`"
 				}
-				if _, err := ctx.Buffer.WriteString(fmt.Sprintf("%s %s ?", factor, operator)); err != nil {
+				if _, err := ctx.Buffer.WriteString(fmt.Sprintf("%s %s ?", sqlTemplate, operator)); err != nil {
 					return err
 				}
 				ctx.Args = append(ctx.Args, valueStr)
@@ -125,11 +145,8 @@ func (d *DB) ConvertExprToSQL(ctx *filter.ConvertContext, expr *exprv1.Expr) err
 					return errors.New("invalid int value")
 				}
 
-				var factor string
-				if identifier == "creator_id" {
-					factor = "`memo`.`creator_id`"
-				}
-				if _, err := ctx.Buffer.WriteString(fmt.Sprintf("%s %s ?", factor, operator)); err != nil {
+				sqlTemplate := filter.GetSQL("table_prefix", dbType) + ".`creator_id`"
+				if _, err := ctx.Buffer.WriteString(fmt.Sprintf("%s %s ?", sqlTemplate, operator)); err != nil {
 					return err
 				}
 				ctx.Args = append(ctx.Args, valueInt)
@@ -141,15 +158,22 @@ func (d *DB) ConvertExprToSQL(ctx *filter.ConvertContext, expr *exprv1.Expr) err
 				if !ok {
 					return errors.New("invalid boolean value for has_task_list")
 				}
-
-				// In MySQL, we can use JSON_EXTRACT to get the value and compare it to 'true' or 'false'
-				compareValue := "false"
-				if valueBool {
-					compareValue = "true"
+				// Use template for boolean comparison
+				var sqlTemplate string
+				if operator == "=" {
+					if valueBool {
+						sqlTemplate = filter.GetSQL("boolean_true", dbType)
+					} else {
+						sqlTemplate = filter.GetSQL("boolean_false", dbType)
+					}
+				} else { // operator == "!="
+					if valueBool {
+						sqlTemplate = filter.GetSQL("boolean_not_true", dbType)
+					} else {
+						sqlTemplate = filter.GetSQL("boolean_not_false", dbType)
+					}
 				}
-
-				// MySQL uses -> as a shorthand for JSON_EXTRACT
-				if _, err := ctx.Buffer.WriteString(fmt.Sprintf("JSON_EXTRACT(`memo`.`payload`, '$.property.hasTaskList') %s CAST('%s' AS JSON)", operator, compareValue)); err != nil {
+				if _, err := ctx.Buffer.WriteString(sqlTemplate); err != nil {
 					return err
 				}
 			}
@@ -157,6 +181,29 @@ func (d *DB) ConvertExprToSQL(ctx *filter.ConvertContext, expr *exprv1.Expr) err
 			if len(v.CallExpr.Args) != 2 {
 				return errors.Errorf("invalid number of arguments for %s", v.CallExpr.Function)
 			}
+
+			// Check if this is "element in collection" syntax
+			if identifier, err := filter.GetIdentExprName(v.CallExpr.Args[1]); err == nil {
+				// This is "element in collection" - the second argument is the collection
+				if !slices.Contains([]string{"tags"}, identifier) {
+					return errors.Errorf("invalid collection identifier for %s: %s", v.CallExpr.Function, identifier)
+				}
+
+				if identifier == "tags" {
+					// Handle "element" in tags
+					element, err := filter.GetConstValue(v.CallExpr.Args[0])
+					if err != nil {
+						return errors.Errorf("first argument must be a constant value for 'element in tags': %v", err)
+					}
+					if _, err := ctx.Buffer.WriteString(filter.GetSQL("json_contains_element", dbType)); err != nil {
+						return err
+					}
+					ctx.Args = append(ctx.Args, filter.GetParameterValue(dbType, "json_contains_element", element))
+				}
+				return nil
+			}
+
+			// Original logic for "identifier in [list]" syntax
 			identifier, err := filter.GetIdentExprName(v.CallExpr.Args[0])
 			if err != nil {
 				return err
@@ -174,27 +221,26 @@ func (d *DB) ConvertExprToSQL(ctx *filter.ConvertContext, expr *exprv1.Expr) err
 				values = append(values, value)
 			}
 			if identifier == "tag" {
-				subcodition := []string{}
+				subconditions := []string{}
 				args := []any{}
 				for _, v := range values {
-					subcodition, args = append(subcodition, "JSON_CONTAINS(JSON_EXTRACT(`memo`.`payload`, '$.tags'), ?)"), append(args, v)
+					subconditions = append(subconditions, filter.GetSQL("json_contains_tag", dbType))
+					args = append(args, filter.GetParameterValue(dbType, "json_contains_tag", v))
 				}
-				if len(subcodition) == 1 {
-					if _, err := ctx.Buffer.WriteString(subcodition[0]); err != nil {
+				if len(subconditions) == 1 {
+					if _, err := ctx.Buffer.WriteString(subconditions[0]); err != nil {
 						return err
 					}
 				} else {
-					if _, err := ctx.Buffer.WriteString(fmt.Sprintf("(%s)", strings.Join(subcodition, " OR "))); err != nil {
+					if _, err := ctx.Buffer.WriteString(fmt.Sprintf("(%s)", strings.Join(subconditions, " OR "))); err != nil {
 						return err
 					}
 				}
 				ctx.Args = append(ctx.Args, args...)
 			} else if identifier == "visibility" {
-				placeholder := []string{}
-				for range values {
-					placeholder = append(placeholder, "?")
-				}
-				if _, err := ctx.Buffer.WriteString(fmt.Sprintf("`memo`.`visibility` IN (%s)", strings.Join(placeholder, ","))); err != nil {
+				placeholders := filter.FormatPlaceholders(dbType, len(values), 1)
+				visibilitySQL := fmt.Sprintf(filter.GetSQL("visibility_in", dbType), strings.Join(placeholders, ","))
+				if _, err := ctx.Buffer.WriteString(visibilitySQL); err != nil {
 					return err
 				}
 				ctx.Args = append(ctx.Args, values...)
@@ -214,7 +260,7 @@ func (d *DB) ConvertExprToSQL(ctx *filter.ConvertContext, expr *exprv1.Expr) err
 			if err != nil {
 				return err
 			}
-			if _, err := ctx.Buffer.WriteString("`memo`.`content` LIKE ?"); err != nil {
+			if _, err := ctx.Buffer.WriteString(filter.GetSQL("content_like", dbType)); err != nil {
 				return err
 			}
 			ctx.Args = append(ctx.Args, fmt.Sprintf("%%%s%%", arg))
@@ -222,17 +268,37 @@ func (d *DB) ConvertExprToSQL(ctx *filter.ConvertContext, expr *exprv1.Expr) err
 	} else if v, ok := expr.ExprKind.(*exprv1.Expr_IdentExpr); ok {
 		identifier := v.IdentExpr.GetName()
 		if !slices.Contains([]string{"pinned", "has_task_list"}, identifier) {
-			return errors.Errorf("invalid identifier for %s", identifier)
+			return errors.Errorf("invalid identifier %s", identifier)
 		}
 		if identifier == "pinned" {
-			if _, err := ctx.Buffer.WriteString("`memo`.`pinned` IS TRUE"); err != nil {
+			if _, err := ctx.Buffer.WriteString(filter.GetSQL("table_prefix", dbType) + ".`pinned` IS TRUE"); err != nil {
 				return err
 			}
 		} else if identifier == "has_task_list" {
-			if _, err := ctx.Buffer.WriteString("JSON_EXTRACT(`memo`.`payload`, '$.property.hasTaskList') = CAST('true' AS JSON)"); err != nil {
+			// Handle has_task_list as a standalone boolean identifier
+			if _, err := ctx.Buffer.WriteString(filter.GetSQL("boolean_check", dbType)); err != nil {
 				return err
 			}
 		}
 	}
 	return nil
 }
+
+func (d *DB) getComparisonOperator(function string) string {
+	switch function {
+	case "_==_":
+		return "="
+	case "_!=_":
+		return "!="
+	case "_<_":
+		return "<"
+	case "_>_":
+		return ">"
+	case "_<=_":
+		return "<="
+	case "_>=_":
+		return ">="
+	default:
+		return "="
+	}
+}

store/db/mysql/memo_filter_test.go

@@ -95,6 +95,26 @@ func TestConvertExprToSQL(t *testing.T) {
 			want:   "UNIX_TIMESTAMP(`memo`.`created_ts`) > ?",
 			args:   []any{time.Now().Unix() - 60*60*24},
 		},
+		{
+			filter: `size(tags) == 0`,
+			want:   "JSON_LENGTH(COALESCE(JSON_EXTRACT(`memo`.`payload`, '$.tags'), JSON_ARRAY())) = ?",
+			args:   []any{int64(0)},
+		},
+		{
+			filter: `size(tags) > 0`,
+			want:   "JSON_LENGTH(COALESCE(JSON_EXTRACT(`memo`.`payload`, '$.tags'), JSON_ARRAY())) > ?",
+			args:   []any{int64(0)},
+		},
+		{
+			filter: `"work" in tags`,
+			want:   "JSON_CONTAINS(JSON_EXTRACT(`memo`.`payload`, '$.tags'), ?)",
+			args:   []any{"work"},
+		},
+		{
+			filter: `size(tags) == 2`,
+			want:   "JSON_LENGTH(COALESCE(JSON_EXTRACT(`memo`.`payload`, '$.tags'), JSON_ARRAY())) = ?",
+			args:   []any{int64(2)},
+		},
 	}
 
 	for _, tt := range tests {

store/db/postgres/memo_filter.go

@@ -12,219 +12,315 @@ import (
 )
 
 func (d *DB) ConvertExprToSQL(ctx *filter.ConvertContext, expr *exprv1.Expr) error {
+	const dbType = filter.PostgreSQLTemplate
+	_, err := d.convertWithParameterIndex(ctx, expr, dbType, len(ctx.Args)+1)
+	return err
+}
+
+func (d *DB) convertWithParameterIndex(ctx *filter.ConvertContext, expr *exprv1.Expr, dbType filter.TemplateDBType, paramIndex int) (int, error) {
+
 	if v, ok := expr.ExprKind.(*exprv1.Expr_CallExpr); ok {
 		switch v.CallExpr.Function {
 		case "_||_", "_&&_":
 			if len(v.CallExpr.Args) != 2 {
-				return errors.Errorf("invalid number of arguments for %s", v.CallExpr.Function)
+				return paramIndex, errors.Errorf("invalid number of arguments for %s", v.CallExpr.Function)
 			}
 			if _, err := ctx.Buffer.WriteString("("); err != nil {
-				return err
+				return paramIndex, err
 			}
-			if err := d.ConvertExprToSQL(ctx, v.CallExpr.Args[0]); err != nil {
-				return err
+			newParamIndex, err := d.convertWithParameterIndex(ctx, v.CallExpr.Args[0], dbType, paramIndex)
+			if err != nil {
+				return paramIndex, err
 			}
 			operator := "AND"
 			if v.CallExpr.Function == "_||_" {
 				operator = "OR"
 			}
 			if _, err := ctx.Buffer.WriteString(fmt.Sprintf(" %s ", operator)); err != nil {
-				return err
+				return paramIndex, err
 			}
-			if err := d.ConvertExprToSQL(ctx, v.CallExpr.Args[1]); err != nil {
-				return err
+			newParamIndex, err = d.convertWithParameterIndex(ctx, v.CallExpr.Args[1], dbType, newParamIndex)
+			if err != nil {
+				return paramIndex, err
 			}
 			if _, err := ctx.Buffer.WriteString(")"); err != nil {
-				return err
+				return paramIndex, err
 			}
+			return newParamIndex, nil
 		case "!_":
 			if len(v.CallExpr.Args) != 1 {
-				return errors.Errorf("invalid number of arguments for %s", v.CallExpr.Function)
+				return paramIndex, errors.Errorf("invalid number of arguments for %s", v.CallExpr.Function)
 			}
 			if _, err := ctx.Buffer.WriteString("NOT ("); err != nil {
-				return err
+				return paramIndex, err
 			}
-			if err := d.ConvertExprToSQL(ctx, v.CallExpr.Args[0]); err != nil {
-				return err
+			newParamIndex, err := d.convertWithParameterIndex(ctx, v.CallExpr.Args[0], dbType, paramIndex)
+			if err != nil {
+				return paramIndex, err
 			}
 			if _, err := ctx.Buffer.WriteString(")"); err != nil {
-				return err
+				return paramIndex, err
 			}
+			return newParamIndex, nil
 		case "_==_", "_!=_", "_<_", "_>_", "_<=_", "_>=_":
 			if len(v.CallExpr.Args) != 2 {
-				return errors.Errorf("invalid number of arguments for %s", v.CallExpr.Function)
+				return paramIndex, errors.Errorf("invalid number of arguments for %s", v.CallExpr.Function)
 			}
+			// Check if the left side is a function call like size(tags)
+			if leftCallExpr, ok := v.CallExpr.Args[0].ExprKind.(*exprv1.Expr_CallExpr); ok {
+				if leftCallExpr.CallExpr.Function == "size" {
+					// Handle size(tags) comparison
+					if len(leftCallExpr.CallExpr.Args) != 1 {
+						return paramIndex, errors.New("size function requires exactly one argument")
+					}
+					identifier, err := filter.GetIdentExprName(leftCallExpr.CallExpr.Args[0])
+					if err != nil {
+						return paramIndex, err
+					}
+					if identifier != "tags" {
+						return paramIndex, errors.Errorf("size function only supports 'tags' identifier, got: %s", identifier)
+					}
+					value, err := filter.GetExprValue(v.CallExpr.Args[1])
+					if err != nil {
+						return paramIndex, err
+					}
+					valueInt, ok := value.(int64)
+					if !ok {
+						return paramIndex, errors.New("size comparison value must be an integer")
+					}
+					operator := d.getComparisonOperator(v.CallExpr.Function)
+
+					if _, err := ctx.Buffer.WriteString(fmt.Sprintf("%s %s %s",
+						filter.GetSQL("json_array_length", dbType), operator,
+						filter.GetParameterPlaceholder(dbType, paramIndex))); err != nil {
+						return paramIndex, err
+					}
+					ctx.Args = append(ctx.Args, valueInt)
+					return paramIndex + 1, nil
+				}
+			}
+
 			identifier, err := filter.GetIdentExprName(v.CallExpr.Args[0])
 			if err != nil {
-				return err
+				return paramIndex, err
 			}
 			if !slices.Contains([]string{"creator_id", "created_ts", "updated_ts", "visibility", "content", "has_task_list"}, identifier) {
-				return errors.Errorf("invalid identifier for %s", v.CallExpr.Function)
+				return paramIndex, errors.Errorf("invalid identifier for %s", v.CallExpr.Function)
 			}
 			value, err := filter.GetExprValue(v.CallExpr.Args[1])
 			if err != nil {
-				return err
-			}
-			operator := "="
-			switch v.CallExpr.Function {
-			case "_==_":
-				operator = "="
-			case "_!=_":
-				operator = "!="
-			case "_<_":
-				operator = "<"
-			case "_>_":
-				operator = ">"
-			case "_<=_":
-				operator = "<="
-			case "_>=_":
-				operator = ">="
+				return paramIndex, err
 			}
+			operator := d.getComparisonOperator(v.CallExpr.Function)
 
 			if identifier == "created_ts" || identifier == "updated_ts" {
-				timestampInt, ok := value.(int64)
+				valueInt, ok := value.(int64)
 				if !ok {
-					return errors.New("invalid timestamp value")
+					return paramIndex, errors.New("invalid integer timestamp value")
 				}
 
-				var factor string
-				if identifier == "created_ts" {
-					factor = "EXTRACT(EPOCH FROM memo.created_ts)"
-				} else if identifier == "updated_ts" {
-					factor = "EXTRACT(EPOCH FROM memo.updated_ts)"
+				timestampSQL := fmt.Sprintf(filter.GetSQL("timestamp_field", dbType), identifier)
+				if _, err := ctx.Buffer.WriteString(fmt.Sprintf("%s %s %s", timestampSQL, operator,
+					filter.GetParameterPlaceholder(dbType, paramIndex))); err != nil {
+					return paramIndex, err
 				}
-				if _, err := ctx.Buffer.WriteString(fmt.Sprintf("%s %s %s", factor, operator, placeholder(len(ctx.Args)+ctx.ArgsOffset+1))); err != nil {
-					return err
-				}
-				ctx.Args = append(ctx.Args, timestampInt)
+				ctx.Args = append(ctx.Args, valueInt)
+				return paramIndex + 1, nil
 			} else if identifier == "visibility" || identifier == "content" {
 				if operator != "=" && operator != "!=" {
-					return errors.Errorf("invalid operator for %s", v.CallExpr.Function)
+					return paramIndex, errors.Errorf("invalid operator for %s", v.CallExpr.Function)
 				}
 				valueStr, ok := value.(string)
 				if !ok {
-					return errors.New("invalid string value")
+					return paramIndex, errors.New("invalid string value")
 				}
 
-				var factor string
+				var sqlTemplate string
 				if identifier == "visibility" {
-					factor = "memo.visibility"
+					sqlTemplate = filter.GetSQL("table_prefix", dbType) + ".visibility"
 				} else if identifier == "content" {
-					factor = "memo.content"
+					sqlTemplate = filter.GetSQL("content_like", dbType)
+					if _, err := ctx.Buffer.WriteString(sqlTemplate); err != nil {
+						return paramIndex, err
+					}
+					ctx.Args = append(ctx.Args, fmt.Sprintf("%%%s%%", valueStr))
+					return paramIndex + 1, nil
 				}
-				if _, err := ctx.Buffer.WriteString(fmt.Sprintf("%s %s %s", factor, operator, placeholder(len(ctx.Args)+ctx.ArgsOffset+1))); err != nil {
-					return err
+				if _, err := ctx.Buffer.WriteString(fmt.Sprintf("%s %s %s", sqlTemplate, operator,
+					filter.GetParameterPlaceholder(dbType, paramIndex))); err != nil {
+					return paramIndex, err
 				}
 				ctx.Args = append(ctx.Args, valueStr)
+				return paramIndex + 1, nil
 			} else if identifier == "creator_id" {
 				if operator != "=" && operator != "!=" {
-					return errors.Errorf("invalid operator for %s", v.CallExpr.Function)
+					return paramIndex, errors.Errorf("invalid operator for %s", v.CallExpr.Function)
 				}
 				valueInt, ok := value.(int64)
 				if !ok {
-					return errors.New("invalid int value")
+					return paramIndex, errors.New("invalid int value")
 				}
 
-				factor := "memo.creator_id"
-				if _, err := ctx.Buffer.WriteString(fmt.Sprintf("%s %s %s", factor, operator, placeholder(len(ctx.Args)+ctx.ArgsOffset+1))); err != nil {
-					return err
+				sqlTemplate := filter.GetSQL("table_prefix", dbType) + ".creator_id"
+				if _, err := ctx.Buffer.WriteString(fmt.Sprintf("%s %s %s", sqlTemplate, operator,
+					filter.GetParameterPlaceholder(dbType, paramIndex))); err != nil {
+					return paramIndex, err
 				}
 				ctx.Args = append(ctx.Args, valueInt)
+				return paramIndex + 1, nil
 			} else if identifier == "has_task_list" {
 				if operator != "=" && operator != "!=" {
-					return errors.Errorf("invalid operator for %s", v.CallExpr.Function)
+					return paramIndex, errors.Errorf("invalid operator for %s", v.CallExpr.Function)
 				}
 				valueBool, ok := value.(bool)
 				if !ok {
-					return errors.New("invalid boolean value for has_task_list")
+					return paramIndex, errors.New("invalid boolean value for has_task_list")
 				}
-
-				// In PostgreSQL, extract the boolean from the JSON and compare it
-				if _, err := ctx.Buffer.WriteString(fmt.Sprintf("(memo.payload->'property'->>'hasTaskList')::boolean %s %s", operator, placeholder(len(ctx.Args)+ctx.ArgsOffset+1))); err != nil {
-					return err
+				// Use parameterized template for boolean comparison (PostgreSQL only)
+				placeholder := filter.GetParameterPlaceholder(dbType, paramIndex)
+				sqlTemplate := fmt.Sprintf(filter.GetSQL("boolean_compare", dbType), operator)
+				sqlTemplate = strings.Replace(sqlTemplate, "?", placeholder, 1)
+				if _, err := ctx.Buffer.WriteString(sqlTemplate); err != nil {
+					return paramIndex, err
 				}
 				ctx.Args = append(ctx.Args, valueBool)
+				return paramIndex + 1, nil
 			}
 		case "@in":
 			if len(v.CallExpr.Args) != 2 {
-				return errors.Errorf("invalid number of arguments for %s", v.CallExpr.Function)
+				return paramIndex, errors.Errorf("invalid number of arguments for %s", v.CallExpr.Function)
 			}
+
+			// Check if this is "element in collection" syntax
+			if identifier, err := filter.GetIdentExprName(v.CallExpr.Args[1]); err == nil {
+				// This is "element in collection" - the second argument is the collection
+				if !slices.Contains([]string{"tags"}, identifier) {
+					return paramIndex, errors.Errorf("invalid collection identifier for %s: %s", v.CallExpr.Function, identifier)
+				}
+
+				if identifier == "tags" {
+					// Handle "element" in tags
+					element, err := filter.GetConstValue(v.CallExpr.Args[0])
+					if err != nil {
+						return paramIndex, errors.Errorf("first argument must be a constant value for 'element in tags': %v", err)
+					}
+					placeholder := filter.GetParameterPlaceholder(dbType, paramIndex)
+					sql := strings.Replace(filter.GetSQL("json_contains_element", dbType), "?", placeholder, 1)
+					if _, err := ctx.Buffer.WriteString(sql); err != nil {
+						return paramIndex, err
+					}
+					ctx.Args = append(ctx.Args, filter.GetParameterValue(dbType, "json_contains_element", element))
+					return paramIndex + 1, nil
+				}
+				return paramIndex, nil
+			}
+
+			// Original logic for "identifier in [list]" syntax
 			identifier, err := filter.GetIdentExprName(v.CallExpr.Args[0])
 			if err != nil {
-				return err
+				return paramIndex, err
 			}
 			if !slices.Contains([]string{"tag", "visibility"}, identifier) {
-				return errors.Errorf("invalid identifier for %s", v.CallExpr.Function)
+				return paramIndex, errors.Errorf("invalid identifier for %s", v.CallExpr.Function)
 			}
 
 			values := []any{}
 			for _, element := range v.CallExpr.Args[1].GetListExpr().Elements {
 				value, err := filter.GetConstValue(element)
 				if err != nil {
-					return err
+					return paramIndex, err
 				}
 				values = append(values, value)
 			}
 			if identifier == "tag" {
-				subcodition := []string{}
+				subconditions := []string{}
 				args := []any{}
+				currentParamIndex := paramIndex
 				for _, v := range values {
-					subcodition, args = append(subcodition, fmt.Sprintf(`memo.payload->'tags' @> jsonb_build_array(%s)`, placeholder(len(ctx.Args)+ctx.ArgsOffset+len(args)+1))), append(args, v)
+					// Use parameter index for each placeholder
+					placeholder := filter.GetParameterPlaceholder(dbType, currentParamIndex)
+					subcondition := strings.Replace(filter.GetSQL("json_contains_tag", dbType), "?", placeholder, 1)
+					subconditions = append(subconditions, subcondition)
+					args = append(args, filter.GetParameterValue(dbType, "json_contains_tag", v))
+					currentParamIndex++
 				}
-				if len(subcodition) == 1 {
-					if _, err := ctx.Buffer.WriteString(subcodition[0]); err != nil {
-						return err
+				if len(subconditions) == 1 {
+					if _, err := ctx.Buffer.WriteString(subconditions[0]); err != nil {
+						return paramIndex, err
 					}
 				} else {
-					if _, err := ctx.Buffer.WriteString(fmt.Sprintf("(%s)", strings.Join(subcodition, " OR "))); err != nil {
-						return err
+					if _, err := ctx.Buffer.WriteString(fmt.Sprintf("(%s)", strings.Join(subconditions, " OR "))); err != nil {
+						return paramIndex, err
 					}
 				}
 				ctx.Args = append(ctx.Args, args...)
+				return paramIndex + len(args), nil
 			} else if identifier == "visibility" {
-				placeholders := []string{}
-				for i := range values {
-					placeholders = append(placeholders, placeholder(len(ctx.Args)+ctx.ArgsOffset+i+1))
-				}
-				if _, err := ctx.Buffer.WriteString(fmt.Sprintf("memo.visibility IN (%s)", strings.Join(placeholders, ","))); err != nil {
-					return err
+				placeholders := filter.FormatPlaceholders(dbType, len(values), paramIndex)
+				visibilitySQL := fmt.Sprintf(filter.GetSQL("visibility_in", dbType), strings.Join(placeholders, ","))
+				if _, err := ctx.Buffer.WriteString(visibilitySQL); err != nil {
+					return paramIndex, err
 				}
 				ctx.Args = append(ctx.Args, values...)
+				return paramIndex + len(values), nil
 			}
 		case "contains":
 			if len(v.CallExpr.Args) != 1 {
-				return errors.Errorf("invalid number of arguments for %s", v.CallExpr.Function)
+				return paramIndex, errors.Errorf("invalid number of arguments for %s", v.CallExpr.Function)
 			}
 			identifier, err := filter.GetIdentExprName(v.CallExpr.Target)
 			if err != nil {
-				return err
+				return paramIndex, err
 			}
 			if identifier != "content" {
-				return errors.Errorf("invalid identifier for %s", v.CallExpr.Function)
+				return paramIndex, errors.Errorf("invalid identifier for %s", v.CallExpr.Function)
 			}
 			arg, err := filter.GetConstValue(v.CallExpr.Args[0])
 			if err != nil {
-				return err
+				return paramIndex, err
 			}
-			if _, err := ctx.Buffer.WriteString("memo.content ILIKE " + placeholder(len(ctx.Args)+ctx.ArgsOffset+1)); err != nil {
-				return err
+			placeholder := filter.GetParameterPlaceholder(dbType, paramIndex)
+			sql := strings.Replace(filter.GetSQL("content_like", dbType), "?", placeholder, 1)
+			if _, err := ctx.Buffer.WriteString(sql); err != nil {
+				return paramIndex, err
 			}
 			ctx.Args = append(ctx.Args, fmt.Sprintf("%%%s%%", arg))
+			return paramIndex + 1, nil
 		}
 	} else if v, ok := expr.ExprKind.(*exprv1.Expr_IdentExpr); ok {
 		identifier := v.IdentExpr.GetName()
 		if !slices.Contains([]string{"pinned", "has_task_list"}, identifier) {
-			return errors.Errorf("invalid identifier %s", identifier)
+			return paramIndex, errors.Errorf("invalid identifier %s", identifier)
 		}
 		if identifier == "pinned" {
-			if _, err := ctx.Buffer.WriteString("memo.pinned IS TRUE"); err != nil {
-				return err
+			if _, err := ctx.Buffer.WriteString(filter.GetSQL("table_prefix", dbType) + ".pinned IS TRUE"); err != nil {
+				return paramIndex, err
 			}
 		} else if identifier == "has_task_list" {
-			if _, err := ctx.Buffer.WriteString("(memo.payload->'property'->>'hasTaskList')::boolean IS TRUE"); err != nil {
-				return err
+			// Handle has_task_list as a standalone boolean identifier
+			if _, err := ctx.Buffer.WriteString(filter.GetSQL("boolean_check", dbType)); err != nil {
+				return paramIndex, err
 			}
 		}
 	}
-	return nil
+	return paramIndex, nil
+}
+
+func (d *DB) getComparisonOperator(function string) string {
+	switch function {
+	case "_==_":
+		return "="
+	case "_!=_":
+		return "!="
+	case "_<_":
+		return "<"
+	case "_>_":
+		return ">"
+	case "_<=_":
+		return "<="
+	case "_>=_":
+		return ">="
+	default:
+		return "="
+	}
 }

store/db/postgres/memo_filter_test.go

@@ -95,6 +95,26 @@ func TestRestoreExprToSQL(t *testing.T) {
 			want:   "EXTRACT(EPOCH FROM memo.created_ts) > $1",
 			args:   []any{time.Now().Unix() - 60*60*24},
 		},
+		{
+			filter: `size(tags) == 0`,
+			want:   "jsonb_array_length(COALESCE(memo.payload->'tags', '[]'::jsonb)) = $1",
+			args:   []any{int64(0)},
+		},
+		{
+			filter: `size(tags) > 0`,
+			want:   "jsonb_array_length(COALESCE(memo.payload->'tags', '[]'::jsonb)) > $1",
+			args:   []any{int64(0)},
+		},
+		{
+			filter: `"work" in tags`,
+			want:   "memo.payload->'tags' @> jsonb_build_array($1)",
+			args:   []any{"work"},
+		},
+		{
+			filter: `size(tags) == 2`,
+			want:   "jsonb_array_length(COALESCE(memo.payload->'tags', '[]'::jsonb)) = $1",
+			args:   []any{int64(2)},
+		},
 	}
 
 	for _, tt := range tests {

store/db/sqlite/memo_filter.go

@@ -12,6 +12,12 @@ import (
 )
 
 func (d *DB) ConvertExprToSQL(ctx *filter.ConvertContext, expr *exprv1.Expr) error {
+	return d.convertWithTemplates(ctx, expr)
+}
+
+func (d *DB) convertWithTemplates(ctx *filter.ConvertContext, expr *exprv1.Expr) error {
+	const dbType = filter.SQLiteTemplate
+
 	if v, ok := expr.ExprKind.(*exprv1.Expr_CallExpr); ok {
 		switch v.CallExpr.Function {
 		case "_||_", "_&&_":
@@ -21,7 +27,7 @@ func (d *DB) ConvertExprToSQL(ctx *filter.ConvertContext, expr *exprv1.Expr) err
 			if _, err := ctx.Buffer.WriteString("("); err != nil {
 				return err
 			}
-			if err := d.ConvertExprToSQL(ctx, v.CallExpr.Args[0]); err != nil {
+			if err := d.convertWithTemplates(ctx, v.CallExpr.Args[0]); err != nil {
 				return err
 			}
 			operator := "AND"
@@ -31,7 +37,7 @@ func (d *DB) ConvertExprToSQL(ctx *filter.ConvertContext, expr *exprv1.Expr) err
 			if _, err := ctx.Buffer.WriteString(fmt.Sprintf(" %s ", operator)); err != nil {
 				return err
 			}
-			if err := d.ConvertExprToSQL(ctx, v.CallExpr.Args[1]); err != nil {
+			if err := d.convertWithTemplates(ctx, v.CallExpr.Args[1]); err != nil {
 				return err
 			}
 			if _, err := ctx.Buffer.WriteString(")"); err != nil {
@@ -44,7 +50,7 @@ func (d *DB) ConvertExprToSQL(ctx *filter.ConvertContext, expr *exprv1.Expr) err
 			if _, err := ctx.Buffer.WriteString("NOT ("); err != nil {
 				return err
 			}
-			if err := d.ConvertExprToSQL(ctx, v.CallExpr.Args[0]); err != nil {
+			if err := d.convertWithTemplates(ctx, v.CallExpr.Args[0]); err != nil {
 				return err
 			}
 			if _, err := ctx.Buffer.WriteString(")"); err != nil {
@@ -54,6 +60,39 @@ func (d *DB) ConvertExprToSQL(ctx *filter.ConvertContext, expr *exprv1.Expr) err
 			if len(v.CallExpr.Args) != 2 {
 				return errors.Errorf("invalid number of arguments for %s", v.CallExpr.Function)
 			}
+			// Check if the left side is a function call like size(tags)
+			if leftCallExpr, ok := v.CallExpr.Args[0].ExprKind.(*exprv1.Expr_CallExpr); ok {
+				if leftCallExpr.CallExpr.Function == "size" {
+					// Handle size(tags) comparison
+					if len(leftCallExpr.CallExpr.Args) != 1 {
+						return errors.New("size function requires exactly one argument")
+					}
+					identifier, err := filter.GetIdentExprName(leftCallExpr.CallExpr.Args[0])
+					if err != nil {
+						return err
+					}
+					if identifier != "tags" {
+						return errors.Errorf("size function only supports 'tags' identifier, got: %s", identifier)
+					}
+					value, err := filter.GetExprValue(v.CallExpr.Args[1])
+					if err != nil {
+						return err
+					}
+					valueInt, ok := value.(int64)
+					if !ok {
+						return errors.New("size comparison value must be an integer")
+					}
+					operator := d.getComparisonOperator(v.CallExpr.Function)
+
+					if _, err := ctx.Buffer.WriteString(fmt.Sprintf("%s %s ?",
+						filter.GetSQL("json_array_length", dbType), operator)); err != nil {
+						return err
+					}
+					ctx.Args = append(ctx.Args, valueInt)
+					return nil
+				}
+			}
+
 			identifier, err := filter.GetIdentExprName(v.CallExpr.Args[0])
 			if err != nil {
 				return err
@@ -65,21 +104,7 @@ func (d *DB) ConvertExprToSQL(ctx *filter.ConvertContext, expr *exprv1.Expr) err
 			if err != nil {
 				return err
 			}
-			operator := "="
-			switch v.CallExpr.Function {
-			case "_==_":
-				operator = "="
-			case "_!=_":
-				operator = "!="
-			case "_<_":
-				operator = "<"
-			case "_>_":
-				operator = ">"
-			case "_<=_":
-				operator = "<="
-			case "_>=_":
-				operator = ">="
-			}
+			operator := d.getComparisonOperator(v.CallExpr.Function)
 
 			if identifier == "created_ts" || identifier == "updated_ts" {
 				valueInt, ok := value.(int64)
@@ -87,13 +112,8 @@ func (d *DB) ConvertExprToSQL(ctx *filter.ConvertContext, expr *exprv1.Expr) err
 					return errors.New("invalid integer timestamp value")
 				}
 
-				var factor string
-				if identifier == "created_ts" {
-					factor = "`memo`.`created_ts`"
-				} else if identifier == "updated_ts" {
-					factor = "`memo`.`updated_ts`"
-				}
-				if _, err := ctx.Buffer.WriteString(fmt.Sprintf("%s %s ?", factor, operator)); err != nil {
+				timestampSQL := fmt.Sprintf(filter.GetSQL("timestamp_field", dbType), identifier)
+				if _, err := ctx.Buffer.WriteString(fmt.Sprintf("%s %s ?", timestampSQL, operator)); err != nil {
 					return err
 				}
 				ctx.Args = append(ctx.Args, valueInt)
@@ -106,13 +126,13 @@ func (d *DB) ConvertExprToSQL(ctx *filter.ConvertContext, expr *exprv1.Expr) err
 					return errors.New("invalid string value")
 				}
 
-				var factor string
+				var sqlTemplate string
 				if identifier == "visibility" {
-					factor = "`memo`.`visibility`"
+					sqlTemplate = filter.GetSQL("table_prefix", dbType) + ".`visibility`"
 				} else if identifier == "content" {
-					factor = "`memo`.`content`"
+					sqlTemplate = filter.GetSQL("table_prefix", dbType) + ".`content`"
 				}
-				if _, err := ctx.Buffer.WriteString(fmt.Sprintf("%s %s ?", factor, operator)); err != nil {
+				if _, err := ctx.Buffer.WriteString(fmt.Sprintf("%s %s ?", sqlTemplate, operator)); err != nil {
 					return err
 				}
 				ctx.Args = append(ctx.Args, valueStr)
@@ -125,11 +145,8 @@ func (d *DB) ConvertExprToSQL(ctx *filter.ConvertContext, expr *exprv1.Expr) err
 					return errors.New("invalid int value")
 				}
 
-				var factor string
-				if identifier == "creator_id" {
-					factor = "`memo`.`creator_id`"
-				}
-				if _, err := ctx.Buffer.WriteString(fmt.Sprintf("%s %s ?", factor, operator)); err != nil {
+				sqlTemplate := filter.GetSQL("table_prefix", dbType) + ".`creator_id`"
+				if _, err := ctx.Buffer.WriteString(fmt.Sprintf("%s %s ?", sqlTemplate, operator)); err != nil {
 					return err
 				}
 				ctx.Args = append(ctx.Args, valueInt)
@@ -141,12 +158,22 @@ func (d *DB) ConvertExprToSQL(ctx *filter.ConvertContext, expr *exprv1.Expr) err
 				if !ok {
 					return errors.New("invalid boolean value for has_task_list")
 				}
-				// In SQLite JSON boolean values are 1 for true and 0 for false
-				compareValue := 0
-				if valueBool {
-					compareValue = 1
+				// Use template for boolean comparison
+				var sqlTemplate string
+				if operator == "=" {
+					if valueBool {
+						sqlTemplate = filter.GetSQL("boolean_true", dbType)
+					} else {
+						sqlTemplate = filter.GetSQL("boolean_false", dbType)
+					}
+				} else { // operator == "!="
+					if valueBool {
+						sqlTemplate = filter.GetSQL("boolean_not_true", dbType)
+					} else {
+						sqlTemplate = filter.GetSQL("boolean_not_false", dbType)
+					}
 				}
-				if _, err := ctx.Buffer.WriteString(fmt.Sprintf("JSON_EXTRACT(`memo`.`payload`, '$.property.hasTaskList') %s %d", operator, compareValue)); err != nil {
+				if _, err := ctx.Buffer.WriteString(sqlTemplate); err != nil {
 					return err
 				}
 			}
@@ -154,6 +181,29 @@ func (d *DB) ConvertExprToSQL(ctx *filter.ConvertContext, expr *exprv1.Expr) err
 			if len(v.CallExpr.Args) != 2 {
 				return errors.Errorf("invalid number of arguments for %s", v.CallExpr.Function)
 			}
+
+			// Check if this is "element in collection" syntax
+			if identifier, err := filter.GetIdentExprName(v.CallExpr.Args[1]); err == nil {
+				// This is "element in collection" - the second argument is the collection
+				if !slices.Contains([]string{"tags"}, identifier) {
+					return errors.Errorf("invalid collection identifier for %s: %s", v.CallExpr.Function, identifier)
+				}
+
+				if identifier == "tags" {
+					// Handle "element" in tags
+					element, err := filter.GetConstValue(v.CallExpr.Args[0])
+					if err != nil {
+						return errors.Errorf("first argument must be a constant value for 'element in tags': %v", err)
+					}
+					if _, err := ctx.Buffer.WriteString(filter.GetSQL("json_contains_element", dbType)); err != nil {
+						return err
+					}
+					ctx.Args = append(ctx.Args, filter.GetParameterValue(dbType, "json_contains_element", element))
+				}
+				return nil
+			}
+
+			// Original logic for "identifier in [list]" syntax
 			identifier, err := filter.GetIdentExprName(v.CallExpr.Args[0])
 			if err != nil {
 				return err
@@ -171,27 +221,26 @@ func (d *DB) ConvertExprToSQL(ctx *filter.ConvertContext, expr *exprv1.Expr) err
 				values = append(values, value)
 			}
 			if identifier == "tag" {
-				subcodition := []string{}
+				subconditions := []string{}
 				args := []any{}
 				for _, v := range values {
-					subcodition, args = append(subcodition, "JSON_EXTRACT(`memo`.`payload`, '$.tags') LIKE ?"), append(args, fmt.Sprintf(`%%"%s"%%`, v))
+					subconditions = append(subconditions, filter.GetSQL("json_contains_tag", dbType))
+					args = append(args, filter.GetParameterValue(dbType, "json_contains_tag", v))
 				}
-				if len(subcodition) == 1 {
-					if _, err := ctx.Buffer.WriteString(subcodition[0]); err != nil {
+				if len(subconditions) == 1 {
+					if _, err := ctx.Buffer.WriteString(subconditions[0]); err != nil {
 						return err
 					}
 				} else {
-					if _, err := ctx.Buffer.WriteString(fmt.Sprintf("(%s)", strings.Join(subcodition, " OR "))); err != nil {
+					if _, err := ctx.Buffer.WriteString(fmt.Sprintf("(%s)", strings.Join(subconditions, " OR "))); err != nil {
 						return err
 					}
 				}
 				ctx.Args = append(ctx.Args, args...)
 			} else if identifier == "visibility" {
-				placeholder := []string{}
-				for range values {
-					placeholder = append(placeholder, "?")
-				}
-				if _, err := ctx.Buffer.WriteString(fmt.Sprintf("`memo`.`visibility` IN (%s)", strings.Join(placeholder, ","))); err != nil {
+				placeholders := filter.FormatPlaceholders(dbType, len(values), 1)
+				visibilitySQL := fmt.Sprintf(filter.GetSQL("visibility_in", dbType), strings.Join(placeholders, ","))
+				if _, err := ctx.Buffer.WriteString(visibilitySQL); err != nil {
 					return err
 				}
 				ctx.Args = append(ctx.Args, values...)
@@ -211,7 +260,7 @@ func (d *DB) ConvertExprToSQL(ctx *filter.ConvertContext, expr *exprv1.Expr) err
 			if err != nil {
 				return err
 			}
-			if _, err := ctx.Buffer.WriteString("`memo`.`content` LIKE ?"); err != nil {
+			if _, err := ctx.Buffer.WriteString(filter.GetSQL("content_like", dbType)); err != nil {
 				return err
 			}
 			ctx.Args = append(ctx.Args, fmt.Sprintf("%%%s%%", arg))
@@ -222,15 +271,34 @@ func (d *DB) ConvertExprToSQL(ctx *filter.ConvertContext, expr *exprv1.Expr) err
 			return errors.Errorf("invalid identifier %s", identifier)
 		}
 		if identifier == "pinned" {
-			if _, err := ctx.Buffer.WriteString("`memo`.`pinned` IS TRUE"); err != nil {
+			if _, err := ctx.Buffer.WriteString(filter.GetSQL("table_prefix", dbType) + ".`pinned` IS TRUE"); err != nil {
 				return err
 			}
 		} else if identifier == "has_task_list" {
 			// Handle has_task_list as a standalone boolean identifier
-			if _, err := ctx.Buffer.WriteString("JSON_EXTRACT(`memo`.`payload`, '$.property.hasTaskList') IS TRUE"); err != nil {
+			if _, err := ctx.Buffer.WriteString(filter.GetSQL("boolean_check", dbType)); err != nil {
 				return err
 			}
 		}
 	}
 	return nil
 }
+
+func (d *DB) getComparisonOperator(function string) string {
+	switch function {
+	case "_==_":
+		return "="
+	case "_!=_":
+		return "!="
+	case "_<_":
+		return "<"
+	case "_>_":
+		return ">"
+	case "_<=_":
+		return "<="
+	case "_>=_":
+		return ">="
+	default:
+		return "="
+	}
+}

store/db/sqlite/memo_filter_test.go

@@ -110,14 +110,40 @@ func TestConvertExprToSQL(t *testing.T) {
 			want:   "`memo`.`created_ts` > ?",
 			args:   []any{time.Now().Unix() - 60*60*24},
 		},
+		{
+			filter: `size(tags) == 0`,
+			want:   "JSON_ARRAY_LENGTH(COALESCE(JSON_EXTRACT(`memo`.`payload`, '$.tags'), JSON_ARRAY())) = ?",
+			args:   []any{int64(0)},
+		},
+		{
+			filter: `size(tags) > 0`,
+			want:   "JSON_ARRAY_LENGTH(COALESCE(JSON_EXTRACT(`memo`.`payload`, '$.tags'), JSON_ARRAY())) > ?",
+			args:   []any{int64(0)},
+		},
+		{
+			filter: `"work" in tags`,
+			want:   "JSON_EXTRACT(`memo`.`payload`, '$.tags') LIKE ?",
+			args:   []any{`%"work"%`},
+		},
+		{
+			filter: `size(tags) == 2`,
+			want:   "JSON_ARRAY_LENGTH(COALESCE(JSON_EXTRACT(`memo`.`payload`, '$.tags'), JSON_ARRAY())) = ?",
+			args:   []any{int64(2)},
+		},
 	}
 
 	for _, tt := range tests {
 		db := &DB{}
 		parsedExpr, err := filter.Parse(tt.filter, filter.MemoFilterCELAttributes...)
+		if err != nil {
+			t.Logf("Failed to parse filter: %s, error: %v", tt.filter, err)
+		}
 		require.NoError(t, err)
 		convertCtx := filter.NewConvertContext()
 		err = db.ConvertExprToSQL(convertCtx, parsedExpr.GetExpr())
+		if err != nil {
+			t.Logf("Failed to convert filter: %s, error: %v", tt.filter, err)
+		}
 		require.NoError(t, err)
 		require.Equal(t, tt.want, convertCtx.Buffer.String())
 		require.Equal(t, tt.args, convertCtx.Args)