sql: fix ALTER INDEX IF EXISTS for non-existing index

pkg/sql/logictest/testdata/logic_test/drop_index

@@ -13,7 +13,9 @@ CREATE TABLE users (
 statement ok
 CREATE TABLE othertable (
    x INT,
-   INDEX baw (x)
+   y INT,
+   INDEX baw (x),
+   INDEX yak (y, x)
 )
 
 statement error index name "baw" is ambiguous
@@ -22,6 +24,27 @@ DROP INDEX baw
 statement error index name "baw" is ambiguous
 DROP INDEX IF EXISTS baw
 
+statement error index "ark" does not exist
+DROP INDEX ark
+
+statement ok
+DROP INDEX IF EXISTS ark
+
+statement error index "ark" does not exist
+DROP INDEX users@ark
+
+statement ok
+DROP INDEX IF EXISTS users@ark
+
+statement ok
+DROP INDEX yak
+
+statement ok
+CREATE INDEX yak ON othertable (y, x)
+
+statement ok
+DROP INDEX IF EXISTS yak
+
 statement ok
 DROP TABLE othertable
 

pkg/sql/logictest/testdata/logic_test/rename_index

@@ -7,9 +7,21 @@ CREATE TABLE users (
   UNIQUE INDEX bar (id, name)
 )
 
+statement ok
+CREATE TABLE users_dupe (
+  id    INT PRIMARY KEY,
+  name  VARCHAR NOT NULL,
+  title VARCHAR,
+  INDEX foo (name),
+  UNIQUE INDEX bar (id, name)
+)
+
 statement ok
 INSERT INTO users VALUES (1, 'tom', 'cat'),(2, 'jerry', 'rat')
 
+statement ok
+INSERT INTO users_dupe VALUES (1, 'tom', 'cat'),(2, 'jerry', 'rat')
+
 query TTBITTBB colnames
 SHOW INDEXES FROM users
 ----
@@ -20,6 +32,16 @@ users       foo         true        2             id           ASC        false
 users       bar         false       1             id           ASC        false    false
 users       bar         false       2             name         ASC        false    false
 
+query TTBITTBB colnames
+SHOW INDEXES FROM users_dupe
+----
+table_name  index_name  non_unique  seq_in_index  column_name  direction  storing  implicit
+users_dupe  primary     false       1             id           ASC        false    false
+users_dupe  foo         true        1             name         ASC        false    false
+users_dupe  foo         true        2             id           ASC        false    true
+users_dupe  bar         false       1             id           ASC        false    false
+users_dupe  bar         false       2             name         ASC        false    false
+
 statement error index name "bar" already exists
 ALTER INDEX users@foo RENAME TO bar
 
@@ -29,11 +51,27 @@ ALTER INDEX users@foo RENAME TO ""
 statement error index "ffo" does not exist
 ALTER INDEX users@ffo RENAME TO ufo
 
+statement error index "ffo" does not exist
+ALTER INDEX ffo RENAME TO ufo
+
+statement error index name "foo" is ambiguous
+ALTER INDEX foo RENAME TO ufo
+
+statement error index name "foo" is ambiguous
+ALTER INDEX IF EXISTS foo RENAME TO ufo
+
 statement ok
 ALTER INDEX IF EXISTS users@ffo RENAME TO ufo
 
+# Regression test for #42399.
+statement ok
+ALTER INDEX IF EXISTS ffo RENAME TO ufo
+
+statement ok
+ALTER INDEX users@foo RENAME TO ufooo
+
 statement ok
-ALTER INDEX users@foo RENAME TO ufoo
+ALTER INDEX IF EXISTS ufooo RENAME TO ufoo
 
 statement ok
 ALTER INDEX ufoo RENAME TO ufo

pkg/sql/parser/parse_test.go

@@ -1100,6 +1100,7 @@ func TestParse(t *testing.T) {
 		{`EXPLAIN ALTER INDEX b RENAME TO b`},
 		{`ALTER INDEX a@b RENAME TO b`},
 		{`ALTER INDEX a@primary RENAME TO like`},
+		{`ALTER INDEX IF EXISTS b RENAME TO b`},
 		{`ALTER INDEX IF EXISTS a@b RENAME TO b`},
 		{`ALTER INDEX IF EXISTS a@primary RENAME TO like`},
 

pkg/sql/rename_index.go

@@ -34,10 +34,14 @@ type renameIndexNode struct {
 //   notes: postgres requires CREATE on the table.
 //          mysql requires ALTER, CREATE, INSERT on the table.
 func (p *planner) RenameIndex(ctx context.Context, n *tree.RenameIndex) (planNode, error) {
-	_, tableDesc, err := expandMutableIndexName(ctx, p, n.Index, true /* requireTable */)
+	_, tableDesc, err := expandMutableIndexName(ctx, p, n.Index, !n.IfExists /* requireTable */)
 	if err != nil {
 		return nil, err
 	}
+	if tableDesc == nil {
+		// IfExists specified and table did not exist -- noop.
+		return newZeroNode(nil /* columns */), nil
+	}
 
 	idx, _, err := tableDesc.FindIndexByName(string(n.Index.Index))
 	if err != nil {