GMS warning on functional indices

enginetest/queries/index_queries.go

@@ -4533,4 +4533,24 @@ var IndexQueries = []ScriptTest{
 			},
 		},
 	},
+	{
+		Name: "functional indices warning",
+		SetUpScript: []string{
+			"CREATE TABLE test (i int, b int)",
+		},
+		Assertions: []ScriptTestAssertion{
+			{
+				Query: "CREATE INDEX idx ON test ((i + b))",
+				Expected: []sql.Row{
+					{types.NewOkResult(0)},
+				},
+			},
+			{
+				Query: "SHOW WARNINGS",
+				Expected: []sql.Row{
+					{"Error", 0, "Index not created, functional indexes not implemented"},
+				},
+			},
+		},
+	},
 }

sql/plan/alter_index.go

@@ -58,6 +58,9 @@ type AlterIndex struct {
 	targetSchema sql.Schema
 	// Columns contains the column names (and possibly lengths) when creating an index
 	Columns []sql.IndexColumn
+	// Expression holds the expression when creating an index
+	// TODO: Not currently implemented. Returns a no-op & warning if used
+	Expression sql.Expression
 	// TODO: This should just use sql.IndexDef
 	// Using states whether you're using BTREE, HASH, or non
 	Using sql.IndexUsing
@@ -79,7 +82,7 @@ var _ sql.Expressioner = (*AlterIndex)(nil)
 var _ sql.Node = (*AlterIndex)(nil)
 var _ sql.CollationCoercible = (*AlterIndex)(nil)
 
-func NewAlterCreateIndex(db sql.Database, table sql.TableNode, ifNotExists bool, indexName string, using sql.IndexUsing, constraint sql.IndexConstraint, columns []sql.IndexColumn, comment string) *AlterIndex {
+func NewAlterCreateIndex(db sql.Database, table sql.TableNode, ifNotExists bool, indexName string, using sql.IndexUsing, constraint sql.IndexConstraint, columns []sql.IndexColumn, expression sql.Expression, comment string) *AlterIndex {
 	return &AlterIndex{
 		Action:      IndexAction_Create,
 		Db:          db,
@@ -89,6 +92,7 @@ func NewAlterCreateIndex(db sql.Database, table sql.TableNode, ifNotExists bool,
 		Using:       using,
 		Constraint:  constraint,
 		Columns:     columns,
+		Expression:  expression,
 		Comment:     comment,
 	}
 }

sql/planbuilder/ddl.go

@@ -617,6 +617,7 @@ func (b *Builder) buildAlterTableClause(inScope *scope, ddl *ast.DDL) []*scope {
 						sql.IndexUsing_BTree,
 						sql.IndexConstraint_Unique,
 						[]sql.IndexColumn{{Name: column.Name.String()}},
+						nil,
 						"",
 					)
 
@@ -981,6 +982,11 @@ func (b *Builder) buildAlterIndex(inScope *scope, ddl *ast.DDL, table *plan.Reso
 
 		columns := b.gatherIndexColumns(ddl.IndexSpec.Columns)
 
+		var indexExpr sql.Expression
+		if ddl.IndexSpec.Expression != nil {
+			indexExpr = b.buildScalar(inScope, ddl.IndexSpec.Expression)
+		}
+
 		var comment string
 		for _, option := range ddl.IndexSpec.Options {
 			if strings.ToLower(option.Name) == strings.ToLower(ast.KeywordString(ast.COMMENT_KEYWORD)) {
@@ -1007,6 +1013,7 @@ func (b *Builder) buildAlterIndex(inScope *scope, ddl *ast.DDL, table *plan.Reso
 			using,
 			constraint,
 			columns,
+			indexExpr,
 			comment,
 		)
 		outScope.node = b.modifySchemaTarget(inScope, createIndex, table.Schema())

sql/rowexec/ddl_iters.go

@@ -2109,6 +2109,13 @@ func (b *BaseBuilder) executeAlterIndex(ctx *sql.Context, n *plan.AlterIndex) er
 
 	switch n.Action {
 	case plan.IndexAction_Create:
+		if n.Expression != nil {
+			// Dolt doesn't currently support creating indices with expression arguments.
+			// If we parse a query attempting to do so, we offer a warning and no-op
+			ctx.Session.Warn(&sql.Warning{Level: "Error", Message: "Index not created, functional indexes not implemented"})
+			return nil
+		}
+
 		if len(n.Columns) == 0 {
 			return plan.ErrCreateIndexMissingColumns.New()
 		}