[ Bug Fix ] Preserve DISTINCT keyword when it appears right after SELECT (#161)

Co-authored-by: Anshal <[email protected]>

Author: anshal21

parser/ast.go

@@ -5694,6 +5694,7 @@ type SelectQuery struct {
 	StatementEnd  Pos
 	With          *WithClause
 	Top           *TopClause
+	HasDistinct   bool
 	SelectItems   []*SelectItem
 	From          *FromClause
 	ArrayJoin     *ArrayJoinClause
@@ -5735,6 +5736,9 @@ func (s *SelectQuery) String() string { // nolint: funlen
 		builder.WriteString(" ")
 	}
 	builder.WriteString("SELECT ")
+	if s.HasDistinct {
+		builder.WriteString("DISTINCT ")
+	}
 	if s.Top != nil {
 		builder.WriteString(s.Top.String())
 		builder.WriteString(" ")

parser/parser_query.go

@@ -834,7 +834,7 @@ func (p *Parser) parseSelectStmt(pos Pos) (*SelectQuery, error) { // nolint: fun
 		return nil, err
 	}
 	// DISTINCT?
-	_ = p.tryConsumeKeywords(KeywordDistinct)
+	hasDistinct := p.tryConsumeKeywords(KeywordDistinct)
 
 	top, err := p.tryParseTopClause(p.Pos())
 	if err != nil {
@@ -961,6 +961,7 @@ func (p *Parser) parseSelectStmt(pos Pos) (*SelectQuery, error) { // nolint: fun
 		SelectPos:    pos,
 		StatementEnd: statementEnd,
 		Top:          top,
+		HasDistinct:  hasDistinct,
 		SelectItems:  selectItems,
 		From:         from,
 		ArrayJoin:    arrayJoin,

parser/testdata/ddl/output/bug_001.sql.golden.json

@@ -57,6 +57,7 @@
         "StatementEnd": 635,
         "With": null,
         "Top": null,
+        "HasDistinct": false,
         "SelectItems": [
           {
             "Expr": {

parser/testdata/ddl/output/create_live_view_basic.sql.golden.json

@@ -82,6 +82,7 @@
         "StatementEnd": 101,
         "With": null,
         "Top": null,
+        "HasDistinct": false,
         "SelectItems": [
           {
             "Expr": {

parser/testdata/ddl/output/create_materialized_view_basic.sql.golden.json

@@ -254,6 +254,7 @@
         "StatementEnd": 537,
         "With": null,
         "Top": null,
+        "HasDistinct": false,
         "SelectItems": [
           {
             "Expr": {

parser/testdata/ddl/output/create_materialized_view_with_definer.sql.golden.json

@@ -180,6 +180,7 @@
         "StatementEnd": 355,
         "With": null,
         "Top": null,
+        "HasDistinct": false,
         "SelectItems": [
           {
             "Expr": {

parser/testdata/ddl/output/create_materialized_view_with_empty_table_schema.sql.golden.json

@@ -151,6 +151,7 @@
         "StatementEnd": 460,
         "With": null,
         "Top": null,
+        "HasDistinct": false,
         "SelectItems": [
           {
             "Expr": {
@@ -245,6 +246,7 @@
                     "StatementEnd": 433,
                     "With": null,
                     "Top": null,
+                    "HasDistinct": false,
                     "SelectItems": [
                       {
                         "Expr": {

parser/testdata/ddl/output/create_materialized_view_with_refresh.sql.golden.json

@@ -147,6 +147,7 @@
         "StatementEnd": 302,
         "With": null,
         "Top": null,
+        "HasDistinct": false,
         "SelectItems": [
           {
             "Expr": {

parser/testdata/ddl/output/create_mv_with_not_op.sql.golden.json

@@ -254,6 +254,7 @@
         "StatementEnd": 559,
         "With": null,
         "Top": null,
+        "HasDistinct": false,
         "SelectItems": [
           {
             "Expr": {

parser/testdata/ddl/output/create_mv_with_order_by.sql.golden.json

@@ -103,6 +103,7 @@
         "StatementEnd": 135,
         "With": null,
         "Top": null,
+        "HasDistinct": false,
         "SelectItems": [
           {
             "Expr": {
@@ -233,6 +234,7 @@
         "StatementEnd": 259,
         "With": null,
         "Top": null,
+        "HasDistinct": false,
         "SelectItems": [
           {
             "Expr": {