fix(restheadspec,resolvespec): stop casting SqlNull-wrapped and citext columns to TEXT in filters

reflect.Type.Kind() on spectypes.SqlNull[T] wrappers (SqlInt16/32/64,
SqlFloat64, SqlBool, SqlString, and embedders like SqlTimeStamp) always
reports reflect.Struct, never the wrapped T. ValidateAndAdjustFilterForColumnType
treated those as "complex" columns and forced CAST(col AS TEXT) on eq/gt/lt
filters, e.g. CAST(atdetail.rid_parent AS TEXT) = '90446096', which can't
use the index on rid_parent.

Add spectypes.UnwrapKind to see through SqlNull wrappers to the underlying
Kind, and use it in GetColumnTypeFromModel so numeric/string SqlNull columns
are recognized correctly and compared natively.

Also stop unconditionally casting to TEXT for LIKE/ILIKE and add
reflection.IsCitextColumn: citext columns are already case-insensitive, so
casting them to TEXT flips to case-sensitive matching and defeats a citext
index.

pkg/reflection/model_utils.go

@@ -9,6 +9,7 @@ import (
 	"time"
 
 	"github.com/bitechdev/ResolveSpec/pkg/modelregistry"
+	"github.com/bitechdev/ResolveSpec/pkg/spectypes"
 )
 
 type PrimaryKeyNameProvider interface {
@@ -728,19 +729,19 @@ func GetColumnTypeFromModel(model interface{}, colName string) reflect.Kind {
 			// Parse JSON tag (format: "name,omitempty")
 			parts := strings.Split(jsonTag, ",")
 			if parts[0] == sourceColName {
-				return field.Type.Kind()
+				return spectypes.UnwrapKind(field.Type)
 			}
 		}
 
 		// Check field name (case-insensitive)
 		if strings.EqualFold(field.Name, sourceColName) {
-			return field.Type.Kind()
+			return spectypes.UnwrapKind(field.Type)
 		}
 
 		// Check snake_case conversion
 		snakeCaseName := ToSnakeCase(field.Name)
 		if snakeCaseName == sourceColName {
-			return field.Type.Kind()
+			return spectypes.UnwrapKind(field.Type)
 		}
 	}
 

pkg/reflection/model_utils_test.go

@@ -3,6 +3,8 @@ package reflection
 import (
 	"reflect"
 	"testing"
+
+	"github.com/bitechdev/ResolveSpec/pkg/spectypes"
 )
 
 // Test models for GORM
@@ -1047,6 +1049,22 @@ func TestGetColumnTypeFromModel(t *testing.T) {
 	}
 }
 
+// SqlNull-wrapped columns (e.g. nullable bigint foreign keys) must report the
+// wrapped value's Kind, not reflect.Struct, so numeric eq/gt/lt filters don't
+// get an unnecessary CAST(... AS TEXT) that defeats the column's index.
+type SqlNullFKModel struct {
+	RidParent spectypes.SqlInt64 `bun:"rid_parent" json:"rid_parent"`
+}
+
+func TestGetColumnTypeFromModel_SqlNullWrapper(t *testing.T) {
+	model := SqlNullFKModel{RidParent: spectypes.NewSqlInt64(90446096)}
+
+	result := GetColumnTypeFromModel(model, "rid_parent")
+	if result != reflect.Int64 {
+		t.Errorf("GetColumnTypeFromModel(rid_parent) = %v, want %v (SqlInt64 must unwrap to its numeric Kind)", result, reflect.Int64)
+	}
+}
+
 // ============= Tests for relation functions =============
 
 // Models for relation testing

pkg/reflection/spectypes_helpers.go

@@ -145,8 +145,16 @@ func IsJSONColumn(model interface{}, colName string) bool {
 // tagDeclaresJSON reports whether an ORM struct tag declares a json/jsonb column
 // type, e.g. `bun:"meta,type:jsonb"` or `gorm:"column:meta;type:json"`.
 func tagDeclaresJSON(tag string) bool {
+	return columnTypeTagValue(tag) == "json" || strings.HasPrefix(columnTypeTagValue(tag), "json(") ||
+		columnTypeTagValue(tag) == "jsonb" || strings.HasPrefix(columnTypeTagValue(tag), "jsonb(")
+}
+
+// columnTypeTagValue extracts the lower-cased value of a `type:` entry from a
+// bun or gorm struct tag, e.g. `bun:"name,type:citext"` -> "citext". Returns ""
+// if the tag carries no `type:` entry.
+func columnTypeTagValue(tag string) string {
 	if tag == "" {
-		return false
+		return ""
 	}
 	for _, part := range strings.FieldsFunc(tag, func(r rune) bool {
 		return r == ',' || r == ';' || r == ' '
@@ -155,12 +163,22 @@ func tagDeclaresJSON(tag string) bool {
 		if !found {
 			continue
 		}
-		value = strings.ToLower(strings.TrimSpace(value))
-		// Match "json" and "jsonb", including parametrised forms just in case.
-		if value == "json" || value == "jsonb" ||
-			strings.HasPrefix(value, "json(") || strings.HasPrefix(value, "jsonb(") {
-			return true
+		return strings.ToLower(strings.TrimSpace(value))
 	}
+	return ""
 }
+
+// IsCitextColumn reports whether colName carries an explicit `type:citext`
+// bun/gorm tag. citext columns must never be CAST(... AS TEXT) for comparisons:
+// that swaps in case-sensitive text semantics and defeats any citext index.
+func IsCitextColumn(model interface{}, colName string) bool {
+	f, ok := getColumnStructField(model, colName)
+	if !ok {
 		return false
 	}
+	tagVal := columnTypeTagValue(f.Tag.Get("bun"))
+	if tagVal == "" {
+		tagVal = columnTypeTagValue(f.Tag.Get("gorm"))
+	}
+	return tagVal == "citext"
+}

pkg/resolvespec/handler.go

@@ -1937,10 +1937,10 @@ func (h *Handler) buildFilterCondition(filter common.FilterOption, model interfa
 		condition = fmt.Sprintf("%s <= ?", filter.Column)
 		args = []interface{}{filter.Value}
 	case "like":
-		condition = fmt.Sprintf("CAST(%s AS TEXT) LIKE ?", filter.Column)
+		condition = fmt.Sprintf("%s LIKE ?", likeColumn(filter.Column, model))
 		args = []interface{}{filter.Value}
 	case "ilike":
-		condition = fmt.Sprintf("CAST(%s AS TEXT) ILIKE ?", filter.Column)
+		condition = fmt.Sprintf("%s ILIKE ?", likeColumn(filter.Column, model))
 		args = []interface{}{filter.Value}
 	case "in":
 		condition, args = common.BuildInCondition(filter.Column, filter.Value)
@@ -1973,6 +1973,18 @@ func (h *Handler) buildFilterCondition(filter common.FilterOption, model interfa
 	return condition, args
 }
 
+// likeColumn returns the column expression to use for LIKE/ILIKE. citext
+// columns are compared natively — they're already case-insensitive, and
+// CAST(... AS TEXT) would switch to case-sensitive matching and defeat a
+// citext index. Every other column is cast to TEXT so LIKE/ILIKE also works
+// against date/time/timestamp and numeric columns.
+func likeColumn(column string, model interface{}) string {
+	if reflection.IsCitextColumn(model, column) {
+		return column
+	}
+	return fmt.Sprintf("CAST(%s AS TEXT)", column)
+}
+
 func (h *Handler) applyFilter(query common.SelectQuery, filter common.FilterOption, model interface{}) common.SelectQuery {
 	// Determine which method to use based on LogicOperator
 	useOrLogic := strings.EqualFold(filter.LogicOperator, "OR")
@@ -2007,10 +2019,10 @@ func (h *Handler) applyFilter(query common.SelectQuery, filter common.FilterOpti
 		condition = fmt.Sprintf("%s <= ?", filter.Column)
 		args = []interface{}{filter.Value}
 	case "like":
-		condition = fmt.Sprintf("CAST(%s AS TEXT) LIKE ?", filter.Column)
+		condition = fmt.Sprintf("%s LIKE ?", likeColumn(filter.Column, model))
 		args = []interface{}{filter.Value}
 	case "ilike":
-		condition = fmt.Sprintf("CAST(%s AS TEXT) ILIKE ?", filter.Column)
+		condition = fmt.Sprintf("%s ILIKE ?", likeColumn(filter.Column, model))
 		args = []interface{}{filter.Value}
 	case "in":
 		condition, args = common.BuildInCondition(filter.Column, filter.Value)

pkg/restheadspec/filter_cast_test.go

@@ -0,0 +1,139 @@
+package restheadspec
+
+import (
+	"reflect"
+	"testing"
+
+	"github.com/bitechdev/ResolveSpec/pkg/common"
+	"github.com/bitechdev/ResolveSpec/pkg/spectypes"
+)
+
+// atdetailModel mirrors the real-world model that triggered this regression:
+// rid_parent is a nullable bigint foreign key, backed by spectypes.SqlInt64
+// (a SqlNull[int64] alias). An eq filter on it was being rendered as
+// CAST(atdetail.rid_parent AS TEXT) = '90446096', which can't use the index
+// on rid_parent. Name is a citext column, which must never be cast to TEXT
+// either (that would switch to case-sensitive matching and lose its index).
+type atdetailModel struct {
+	RidParent spectypes.SqlInt64 `json:"rid_parent" bun:"rid_parent"`
+	Name      string             `json:"name" bun:"name,type:citext"`
+}
+
+func TestValidateAndAdjustFilterForColumnType_SqlNullNumeric(t *testing.T) {
+	h := &Handler{}
+	model := atdetailModel{}
+
+	filter := &common.FilterOption{Column: "rid_parent", Operator: "eq", Value: "90446096"}
+	info := h.ValidateAndAdjustFilterForColumnType(filter, model)
+
+	if info.NeedsCast {
+		t.Fatalf("expected NeedsCast=false for a numeric SqlInt64 column with a numeric value, got true")
+	}
+	if !info.IsNumericType {
+		t.Fatalf("expected IsNumericType=true for a SqlInt64 column")
+	}
+	if v, ok := filter.Value.(int64); !ok || v != 90446096 {
+		t.Fatalf("expected filter.Value to be converted to int64(90446096), got %#v", filter.Value)
+	}
+}
+
+func TestApplyFilter_SqlNullNumeric_NoCastKeepsIndexUsable(t *testing.T) {
+	h := &Handler{}
+	model := atdetailModel{}
+
+	filter := common.FilterOption{Column: "rid_parent", Operator: "eq", Value: "90446096"}
+	castInfo := h.ValidateAndAdjustFilterForColumnType(&filter, model)
+
+	q := &jsonCapQuery{}
+	h.applyFilter(q, filter, "public.atdetail", castInfo.NeedsCast, "AND", model)
+
+	c := q.only(t)
+	const want = "atdetail.rid_parent = ?"
+	if c.query != want {
+		t.Fatalf("query = %q, want %q (must not CAST a numeric column to TEXT)", c.query, want)
+	}
+	if !reflect.DeepEqual(c.args, []interface{}{int64(90446096)}) {
+		t.Fatalf("args = %#v", c.args)
+	}
+}
+
+// TestFieldFilterHeader_SqlNullNumeric_EndToEnd reproduces the exact reported
+// regression: a request carrying the header
+//
+//	x-fieldfilter-rid_parent: 90446096
+//
+// against a model whose rid_parent field is a nullable bigint (spectypes.SqlInt64).
+// Before the fix, this parsed to a filter that got CAST(atdetail.rid_parent AS TEXT) = '90446096',
+// making the query unable to use the index on rid_parent. It must now parse to
+// a native "atdetail.rid_parent = ?" comparison with an int64 argument.
+func TestFieldFilterHeader_SqlNullNumeric_EndToEnd(t *testing.T) {
+	h := NewHandler(nil, nil)
+	model := atdetailModel{}
+
+	req := &MockRequest{
+		headers: map[string]string{
+			"x-fieldfilter-rid_parent": "90446096",
+		},
+		queryParams: map[string]string{},
+	}
+
+	options := h.parseOptionsFromHeaders(req, model)
+	if len(options.Filters) != 1 {
+		t.Fatalf("expected 1 filter parsed from x-fieldfilter-rid_parent, got %d: %+v", len(options.Filters), options.Filters)
+	}
+
+	filter := options.Filters[0]
+	if filter.Column != "rid_parent" || filter.Operator != "eq" {
+		t.Fatalf("unexpected parsed filter: %+v", filter)
+	}
+	if filter.Value != "90446096" {
+		t.Fatalf("expected raw header string value before type validation, got %#v", filter.Value)
+	}
+
+	// This is the exact step that decided whether to CAST: ValidateAndAdjustFilterForColumnType
+	// used to see reflect.Struct for the SqlInt64-wrapped column and cast to TEXT.
+	castInfo := h.ValidateAndAdjustFilterForColumnType(&filter, model)
+	if castInfo.NeedsCast {
+		t.Fatalf("regression: numeric SqlInt64 column x-fieldfilter-rid_parent got NeedsCast=true, " +
+			"which renders CAST(atdetail.rid_parent AS TEXT) = '90446096' and defeats the column's index")
+	}
+
+	q := &jsonCapQuery{}
+	h.applyFilter(q, filter, "public.atdetail", castInfo.NeedsCast, filter.LogicOperator, model)
+
+	c := q.only(t)
+	const want = "atdetail.rid_parent = ?"
+	if c.query != want {
+		t.Fatalf("SQL condition = %q, want %q (no CAST, so the rid_parent index can still be used)", c.query, want)
+	}
+	if !reflect.DeepEqual(c.args, []interface{}{int64(90446096)}) {
+		t.Fatalf("args = %#v, want [int64(90446096)]", c.args)
+	}
+}
+
+func TestApplyFilter_Citext_NeverCastForEqOrIlike(t *testing.T) {
+	h := &Handler{}
+	model := atdetailModel{}
+
+	t.Run("eq", func(t *testing.T) {
+		filter := common.FilterOption{Column: "name", Operator: "eq", Value: "Acme"}
+		castInfo := h.ValidateAndAdjustFilterForColumnType(&filter, model)
+		if castInfo.NeedsCast {
+			t.Fatalf("citext column must never need a CAST")
+		}
+		q := &jsonCapQuery{}
+		h.applyFilter(q, filter, "public.atdetail", castInfo.NeedsCast, "AND", model)
+		if c := q.only(t); c.query != "atdetail.name = ?" {
+			t.Fatalf("query = %q", c.query)
+		}
+	})
+
+	t.Run("ilike", func(t *testing.T) {
+		filter := common.FilterOption{Column: "name", Operator: "ilike", Value: "%acme%"}
+		q := &jsonCapQuery{}
+		h.applyFilter(q, filter, "public.atdetail", false, "AND", model)
+		if c := q.only(t); c.query != "atdetail.name ILIKE ?" {
+			t.Fatalf("query = %q, want no CAST for a citext column", c.query)
+		}
+	})
+}

pkg/restheadspec/handler.go

@@ -2325,6 +2325,13 @@ func (h *Handler) applyFilter(query common.SelectQuery, filter common.FilterOpti
 		qualifiedColumn = fmt.Sprintf("CAST(%s AS TEXT)", rawQualifiedColumn)
 	}
 
+	// citext columns already compare case-insensitively; casting to TEXT for
+	// LIKE/ILIKE would switch to case-sensitive matching and defeat a citext index.
+	likeColumn := rawQualifiedColumn
+	if !reflection.IsCitextColumn(model, filter.Column) {
+		likeColumn = fmt.Sprintf("CAST(%s AS TEXT)", rawQualifiedColumn)
+	}
+
 	switch strings.ToLower(filter.Operator) {
 	case "eq", "equals":
 		return applyWhere(fmt.Sprintf("%s = ?", qualifiedColumn), filter.Value)
@@ -2339,11 +2346,14 @@ func (h *Handler) applyFilter(query common.SelectQuery, filter common.FilterOpti
 	case "lte", "less_than_equals", "le":
 		return applyWhere(fmt.Sprintf("%s <= ?", qualifiedColumn), filter.Value)
 	case "like":
-		// Always cast to TEXT for LIKE/ILIKE to support date/time/timestamp columns
-		return applyWhere(fmt.Sprintf("CAST(%s AS TEXT) LIKE ?", rawQualifiedColumn), filter.Value)
+		// Cast to TEXT for LIKE to support date/time/timestamp columns; citext
+		// columns are compared natively (see likeColumn above).
+		return applyWhere(fmt.Sprintf("%s LIKE ?", likeColumn), filter.Value)
 	case "ilike":
-		// Always cast to TEXT for LIKE/ILIKE to support date/time/timestamp columns
-		return applyWhere(fmt.Sprintf("CAST(%s AS TEXT) ILIKE ?", rawQualifiedColumn), filter.Value)
+		// Cast to TEXT for ILIKE to support date/time/timestamp columns; citext
+		// columns are compared natively (see likeColumn above) since citext is
+		// already case-insensitive.
+		return applyWhere(fmt.Sprintf("%s ILIKE ?", likeColumn), filter.Value)
 	case "in":
 		cond, inArgs := common.BuildInCondition(qualifiedColumn, filter.Value)
 		if cond == "" {
@@ -2421,8 +2431,12 @@ func (h *Handler) applyOrFilterGroup(query common.SelectQuery, filters []*common
 
 		op := strings.ToLower(filter.Operator)
 		if op == "like" || op == "ilike" {
-			// Always cast to TEXT for LIKE/ILIKE to support date/time/timestamp columns
+			// Cast to TEXT for LIKE/ILIKE to support date/time/timestamp columns.
+			// citext columns are left native: they're already case-insensitive and
+			// casting would defeat a citext index.
+			if !reflection.IsCitextColumn(model, filter.Column) {
 				qualifiedColumn = fmt.Sprintf("CAST(%s AS TEXT)", rawQualifiedColumn)
+			}
 		} else if castInfo[i].NeedsCast {
 			// Apply casting to text if needed for non-numeric columns or non-numeric values
 			qualifiedColumn = fmt.Sprintf("CAST(%s AS TEXT)", rawQualifiedColumn)

pkg/restheadspec/headers.go

@@ -1466,6 +1466,12 @@ func (h *Handler) ValidateAndAdjustFilterForColumnType(filter *common.FilterOpti
 		return ColumnCastInfo{NeedsCast: false, IsNumericType: false}
 	}
 
+	// Never cast citext columns to TEXT: CAST(col AS TEXT) swaps in case-sensitive
+	// comparison semantics and prevents PostgreSQL from using a citext index.
+	if reflection.IsCitextColumn(model, filter.Column) {
+		return ColumnCastInfo{NeedsCast: false, IsNumericType: false}
+	}
+
 	colType := reflection.GetColumnTypeFromModel(model, filter.Column)
 	if colType == reflect.Invalid {
 		// Column not found in model, no casting needed

pkg/spectypes/type_names.go

@@ -97,3 +97,27 @@ func IsJSONType(t reflect.Type) bool {
 	n, ok := SQLTypeName(t)
 	return ok && (n == "jsonb" || n == "json")
 }
+
+// UnwrapKind returns the reflect.Kind to use when reasoning about a column's
+// comparability (numeric vs. string vs. other) for filter building. Plain Go
+// types return their own Kind unchanged. spectypes.SqlNull[T] wrappers (and
+// types that embed one, such as SqlTimeStamp/SqlDate/SqlTime) always report
+// reflect.Struct for their own Kind even when T is an int64 or string, which
+// would otherwise make numeric/text columns look "complex" and force an
+// unnecessary CAST(... AS TEXT) that defeats native column indexes. For those
+// wrappers, UnwrapKind returns the Kind of the wrapped value T instead.
+func UnwrapKind(t reflect.Type) reflect.Kind {
+	for t != nil && t.Kind() == reflect.Pointer {
+		t = t.Elem()
+	}
+	if t == nil {
+		return reflect.Invalid
+	}
+	if t.Kind() != reflect.Struct || t.PkgPath() != pkgPath {
+		return t.Kind()
+	}
+	if f, ok := t.FieldByName("Val"); ok {
+		return f.Type.Kind()
+	}
+	return t.Kind()
+}