Enable functional index support

postgres/parser/sem/tree/format.go

@@ -442,9 +442,9 @@ func AsStringWithFQNames(n NodeFormatter, ann *Annotations) string {
 	return ctx.CloseAndGetString()
 }
 
-// AsString pretty prints a node to a string.
+// AsString pretty prints a node to a string, with unquoted identifiers.
 func AsString(n NodeFormatter) string {
-	return AsStringWithFlags(n, FmtSimple)
+	return AsStringWithFlags(n, FmtSimple|FmtBareIdentifiers)
 }
 
 // ErrString pretty prints a node to a string. Identifiers are not quoted.

server/analyzer/validate_create_table.go

@@ -124,6 +124,10 @@ func schToColMap(sch sql.Schema) map[string]*sql.Column {
 func validateIndex(ctx *sql.Context, colMap map[string]*sql.Column, idxDef *sql.IndexDef) error {
 	seenCols := make(map[string]struct{})
 	for _, idxCol := range idxDef.Columns {
+		if idxCol.Expression != nil {
+			continue
+		}
+
 		schCol, exists := colMap[strings.ToLower(idxCol.Name)]
 		if !exists {
 			return sql.ErrKeyColumnDoesNotExist.New(idxCol.Name)

server/ast/index_elem.go

@@ -27,10 +27,6 @@ import (
 func nodeIndexElemList(ctx *Context, node tree.IndexElemList) ([]*vitess.IndexField, error) {
 	vitessIndexColumns := make([]*vitess.IndexField, 0, len(node))
 	for _, inputColumn := range node {
-		if inputColumn.Expr != nil {
-			return nil, errors.Errorf("expression index attribute is not yet supported")
-		}
-
 		if inputColumn.Collation != "" {
 			logrus.Warn("index attribute collation is not yet supported, ignoring")
 		}

server/tables/information_schema/columns_table.go

@@ -204,6 +204,9 @@ func getRowsFromTable(ctx *sql.Context, db information_schema.DbWithNames, t sql
 
 	tblName := t.Name()
 	for i, col := range information_schema.SchemaForTable(t, db.Database, allColsWithDefaultValue) {
+		if col.HiddenSystem {
+			continue
+		}
 		r := getRowFromColumn(ctx, i, col, db.CatalogName, db.SchemaName, tblName)
 		if r != nil {
 			rows = append(rows, r)

testing/go/enginetest/doltgres_engine_test.go

@@ -792,6 +792,12 @@ func TestIndexes(t *testing.T) {
 	enginetest.TestIndexes(t, harness)
 }
 
+func TestIndexedExpressions(t *testing.T) {
+	harness := newDoltgresServerHarness(t)
+	defer harness.Close()
+	enginetest.TestIndexedExpressions(t, harness)
+}
+
 func TestIndexPrefix(t *testing.T) {
 	t.Skip()
 	harness := newDoltgresServerHarness(t)

testing/go/enginetest/doltgres_harness_test.go

@@ -113,12 +113,23 @@ var defaultSkippedQueries = []string{
 	"show create table fk_tbl",   // we create an extra key for the FK that vanilla gms does not
 	"show indexes from",          // we create / expose extra indexes (for foreign keys)
 	"show global variables like", // we set extra variables
+	"show columns from",          // MySQL SHOW variant with no PostgreSQL equivalent
+	"show extended columns from", // MySQL SHOW variant with no PostgreSQL equivalent
+
 	// unsupported doltgres syntax
 	// " WITH ",
 	// " OVER ",
 	// string functions are broken due to incompatible types
 	"HEX(",
 	"TO_BASE64(",
+	// MySQL-specific functions not supported in doltgresql
+	"json_unquote", // MySQL JSON function
+	"year(",        // YEAR() functional index hits a type-incompatibility in doltgresql
+
+	// MySQL-specific operators and syntax not supported in PostgreSQL
+	"<=>",           // null-safe equality (PostgreSQL uses IS NOT DISTINCT FROM)
+	"modify column", // MySQL ALTER TABLE MODIFY COLUMN syntax
+	"column first",  // MySQL ADD COLUMN ... FIRST positioning
 }
 
 // Setup sets the setup scripts for this DoltHarness's engine
@@ -729,6 +740,10 @@ func getDmlResult(rows pgx.Rows, query string) (sql.Row, bool) {
 		return sql.NewRow(gmstypes.NewOkResult(0)), true
 	case strings.HasPrefix(tag.String(), "ALTER TABLE"):
 		return sql.NewRow(gmstypes.NewOkResult(0)), true
+	case strings.HasPrefix(tag.String(), "CREATE INDEX"):
+		return sql.NewRow(gmstypes.NewOkResult(0)), true
+	case strings.HasPrefix(tag.String(), "DROP INDEX"):
+		return sql.NewRow(gmstypes.NewOkResult(0)), true
 	case strings.HasPrefix(tag.String(), "TRUNCATE"):
 		return sql.NewRow(gmstypes.NewOkResult(0)), true
 	case strings.HasPrefix(tag.String(), "SET"):
@@ -814,12 +829,15 @@ func unwrapResultColumn(v any) (any, error) {
 	}
 }
 
+// IsServerBacked implements enginetest.ServerBackedEngine, marking DoltgresQueryEngine
+// as a server-backed engine so that plan-inspection checks (evalIndexTest, etc.) are
+// skipped, matching the behavior of GMS's own ServerQueryEngine.
+func (d *DoltgresQueryEngine) IsServerBacked() bool { return true }
+
 func (d *DoltgresQueryEngine) EngineAnalyzer() *analyzer.Analyzer {
 	// TODO: this is a shim to get simple tests to work, we need to restructure the tests to not require access to
 	//  an analyzer
-	catalog := &analyzer.Catalog{}
-	catalog.AuthHandler = sql.GetAuthorizationHandlerFactory().CreateHandler(catalog)
-
+	catalog := analyzer.NewCatalog(nil, sql.EngineOverrides{})
 	return &analyzer.Analyzer{
 		Catalog: catalog,
 	}

testing/go/index_test.go

@@ -1076,10 +1076,6 @@ func TestBasicIndexing(t *testing.T) {
 					// ignored warning-generating unsupported options
 					Query: "CREATE INDEX v1_idx ON test(v1 varchar_pattern_ops) WITH (storage_opt1 = foo) TABLESPACE tablespace_name;",
 				},
-				{
-					Query:       "CREATE INDEX v1_idx2 ON test( (concat(v1, v1)) ) ;",
-					ExpectedErr: "not yet supported",
-				},
 				{
 					Query:       "CREATE INDEX v1_idx2 ON test using hash (v1);",
 					ExpectedErr: "not yet supported",