sql: handle companion array name conflicts in ALTER TYPE

In cases of a name collisions of a companion array type when changing a
type's schema, the schemachanger was not handling it well. This change
addresses that and adds a test.

Supports: #168255

Part of: #164216

Epic: CRDB-31325

Release note: None

Author: bghal

pkg/sql/alter_type.go

@@ -356,6 +356,8 @@ func (p *planner) setTypeSchema(ctx context.Context, n *alterTypeNode, schema st
 		return err
 	}
 
+	// The prepareSetSchema checks the primary type's name. The name of the
+	// companion array is collision checked below.
 	desiredSchemaID, err := p.prepareSetSchema(ctx, n.prefix.Database, typeDesc, schema)
 	if err != nil {
 		return err
@@ -367,16 +369,31 @@ func (p *planner) setTypeSchema(ctx context.Context, n *alterTypeNode, schema st
 		return nil
 	}
 
-	err = p.performRenameTypeDesc(
-		ctx, typeDesc, typeDesc.Name, desiredSchemaID, tree.AsStringWithFQNames(n.n, p.Ann()),
-	)
-
+	arrayDesc, err := p.Descriptors().MutableByID(p.txn).Type(ctx, n.desc.ArrayTypeID)
 	if err != nil {
 		return err
 	}
 
-	arrayDesc, err := p.Descriptors().MutableByID(p.txn).Type(ctx, n.desc.ArrayTypeID)
-	if err != nil {
+	// The CheckObjectNameCollision checks that the companion array can be moved
+	// without colliding with
+	//
+	// This is consistent with the PG behavior which itself is inconsistent:
+	// `SET SCHEMA` errors on collision while `ALTER TYPE ... RENAME` auto-resolves
+	// conflicts on companion array names.
+	if err := descs.CheckObjectNameCollision(
+		ctx,
+		p.Descriptors(),
+		p.txn,
+		typeDesc.GetParentID(),
+		desiredSchemaID,
+		tree.NewUnqualifiedTypeName(arrayDesc.GetName()),
+	); err != nil {
+		return err
+	}
+
+	if err := p.performRenameTypeDesc(
+		ctx, typeDesc, typeDesc.Name, desiredSchemaID, tree.AsStringWithFQNames(n.n, p.Ann()),
+	); err != nil {
 		return err
 	}
 

pkg/sql/logictest/testdata/logic_test/set_schema

@@ -590,3 +590,67 @@ true
 user testuser
 
 subtest end
+
+subtest array_type_name_conflict
+
+statement ok
+CREATE SCHEMA IF NOT EXISTS ocean
+
+statement ok
+CREATE SCHEMA IF NOT EXISTS stream
+
+statement ok
+CREATE TYPE ocean.salmon AS ENUM ('sockeye', 'king', 'atlantic');
+
+statement ok
+CREATE TYPE stream."_salmon" AS ENUM ('steelhead', 'cherry');
+
+# The companion array type "_salmon" collides.
+statement error pq: type "test.stream._salmon" already exists
+ALTER TYPE ocean.salmon SET SCHEMA stream
+
+# Verify the source type and array are still usable in the original schema.
+statement ok
+SELECT 'sockeye'::ocean.salmon
+
+statement ok
+SELECT ARRAY['sockeye']::ocean._salmon
+
+# The target schema should not contain the primary type.
+query error pq: type "stream.salmon" does not exist
+SELECT NULL::stream.salmon
+
+user testuser
+
+subtest end
+
+# Regression test: The companion array type collides with a table in the destination schema.
+subtest array_type_table_collision
+
+user root
+
+statement ok
+CREATE SCHEMA IF NOT EXISTS lake
+
+statement ok
+CREATE SCHEMA IF NOT EXISTS pond
+
+statement ok
+CREATE TYPE lake.trout AS ENUM ('brown', 'rainbow');
+
+statement ok
+CREATE TABLE pond."_trout" (id INT PRIMARY KEY)
+
+statement error pq: relation "test.pond._trout" already exists
+ALTER TYPE lake.trout SET SCHEMA pond
+
+statement ok
+SELECT 'brown'::lake.trout
+
+# The target schema should not contain the primary type.
+query error pq: type "pond.trout" does not exist
+SELECT NULL::pond.trout
+
+user testuser
+
+subtest end