sql: add syntax to create unique constraints without an index

This commit adds support for the syntax `... UNIQUE WITHOUT INDEX ...`,
both when adding UNIQUE constraints and when adding UNIQUE columns. Using
this syntax will currently return the error "unique constraints without
an index are not yet supported", but support for the syntax serves as a
starting point for adding support for these unique constraints.

Informs cockroachdb#41535

Release note (sql change): Added support for using the syntax
`... UNIQUE WITHOUT INDEX ...` in CREATE TABLE and ALTER TABLE statements,
both when defining columns and unique constraints. Although this syntax
can now be parsed successfully, using this syntax currently returns an
error "unique constraints without an index are not yet supported".

docs/generated/sql/bnf/col_qualification.bnf

@@ -1,7 +1,7 @@
 col_qualification ::=
 	'CONSTRAINT' constraint_name 'NOT' 'NULL'
 	| 'CONSTRAINT' constraint_name 'NULL'
-	| 'CONSTRAINT' constraint_name 'UNIQUE'
+	| 'CONSTRAINT' constraint_name 'UNIQUE' opt_without_index
 	| 'CONSTRAINT' constraint_name 'PRIMARY' 'KEY'
 	| 'CONSTRAINT' constraint_name 'PRIMARY' 'KEY' 'USING' 'HASH' 'WITH' 'BUCKET_COUNT' '=' n_buckets
 	| 'CONSTRAINT' constraint_name 'CHECK' '(' a_expr ')'
@@ -10,7 +10,7 @@ col_qualification ::=
 	| 'CONSTRAINT' constraint_name generated_as '(' a_expr ')' 'STORED'
 	| 'NOT' 'NULL'
 	| 'NULL'
-	| 'UNIQUE'
+	| 'UNIQUE' opt_without_index
 	| 'PRIMARY' 'KEY'
 	| 'PRIMARY' 'KEY' 'USING' 'HASH' 'WITH' 'BUCKET_COUNT' '=' n_buckets
 	| 'CHECK' '(' a_expr ')'

docs/generated/sql/bnf/stmt_block.bnf

@@ -2198,7 +2198,7 @@ constraint_name ::=
 
 constraint_elem ::=
 	'CHECK' '(' a_expr ')'
-	| 'UNIQUE' '(' index_params ')' opt_storing opt_interleave opt_partition_by opt_where_clause
+	| 'UNIQUE' opt_without_index '(' index_params ')' opt_storing opt_interleave opt_partition_by opt_where_clause
 	| 'PRIMARY' 'KEY' '(' index_params ')' opt_hash_sharded opt_interleave
 	| 'FOREIGN' 'KEY' '(' name_list ')' 'REFERENCES' table_name opt_column_list key_match reference_actions
 
@@ -2487,6 +2487,10 @@ col_qualification ::=
 	| 'CREATE' 'FAMILY'
 	| 'CREATE' 'IF' 'NOT' 'EXISTS' 'FAMILY' family_name
 
+opt_without_index ::=
+	'WITHOUT' 'INDEX'
+	| 
+
 key_match ::=
 	'MATCH' 'SIMPLE'
 	| 'MATCH' 'FULL'
@@ -2730,7 +2734,7 @@ create_as_constraint_elem ::=
 col_qualification_elem ::=
 	'NOT' 'NULL'
 	| 'NULL'
-	| 'UNIQUE'
+	| 'UNIQUE' opt_without_index
 	| 'PRIMARY' 'KEY'
 	| 'PRIMARY' 'KEY' 'USING' 'HASH' 'WITH' 'BUCKET_COUNT' '=' a_expr
 	| 'CHECK' '(' a_expr ')'

docs/generated/sql/bnf/table_constraint.bnf

@@ -1,17 +1,17 @@
 table_constraint ::=
 	'CONSTRAINT' constraint_name 'CHECK' '(' a_expr ')'
-	| 'CONSTRAINT' constraint_name 'UNIQUE' '(' index_params ')' 'COVERING' '(' name_list ')' opt_interleave opt_partition_by opt_where_clause
-	| 'CONSTRAINT' constraint_name 'UNIQUE' '(' index_params ')' 'STORING' '(' name_list ')' opt_interleave opt_partition_by opt_where_clause
-	| 'CONSTRAINT' constraint_name 'UNIQUE' '(' index_params ')' 'INCLUDE' '(' name_list ')' opt_interleave opt_partition_by opt_where_clause
-	| 'CONSTRAINT' constraint_name 'UNIQUE' '(' index_params ')'  opt_interleave opt_partition_by opt_where_clause
+	| 'CONSTRAINT' constraint_name 'UNIQUE' opt_without_index '(' index_params ')' 'COVERING' '(' name_list ')' opt_interleave opt_partition_by opt_where_clause
+	| 'CONSTRAINT' constraint_name 'UNIQUE' opt_without_index '(' index_params ')' 'STORING' '(' name_list ')' opt_interleave opt_partition_by opt_where_clause
+	| 'CONSTRAINT' constraint_name 'UNIQUE' opt_without_index '(' index_params ')' 'INCLUDE' '(' name_list ')' opt_interleave opt_partition_by opt_where_clause
+	| 'CONSTRAINT' constraint_name 'UNIQUE' opt_without_index '(' index_params ')'  opt_interleave opt_partition_by opt_where_clause
 	| 'CONSTRAINT' constraint_name 'PRIMARY' 'KEY' '(' index_params ')' 'USING' 'HASH' 'WITH' 'BUCKET_COUNT' '=' n_buckets opt_interleave
 	| 'CONSTRAINT' constraint_name 'PRIMARY' 'KEY' '(' index_params ')'  opt_interleave
 	| 'CONSTRAINT' constraint_name 'FOREIGN' 'KEY' '(' name_list ')' 'REFERENCES' table_name opt_column_list key_match reference_actions
 	| 'CHECK' '(' a_expr ')'
-	| 'UNIQUE' '(' index_params ')' 'COVERING' '(' name_list ')' opt_interleave opt_partition_by opt_where_clause
-	| 'UNIQUE' '(' index_params ')' 'STORING' '(' name_list ')' opt_interleave opt_partition_by opt_where_clause
-	| 'UNIQUE' '(' index_params ')' 'INCLUDE' '(' name_list ')' opt_interleave opt_partition_by opt_where_clause
-	| 'UNIQUE' '(' index_params ')'  opt_interleave opt_partition_by opt_where_clause
+	| 'UNIQUE' opt_without_index '(' index_params ')' 'COVERING' '(' name_list ')' opt_interleave opt_partition_by opt_where_clause
+	| 'UNIQUE' opt_without_index '(' index_params ')' 'STORING' '(' name_list ')' opt_interleave opt_partition_by opt_where_clause
+	| 'UNIQUE' opt_without_index '(' index_params ')' 'INCLUDE' '(' name_list ')' opt_interleave opt_partition_by opt_where_clause
+	| 'UNIQUE' opt_without_index '(' index_params ')'  opt_interleave opt_partition_by opt_where_clause
 	| 'PRIMARY' 'KEY' '(' index_params ')' 'USING' 'HASH' 'WITH' 'BUCKET_COUNT' '=' n_buckets opt_interleave
 	| 'PRIMARY' 'KEY' '(' index_params ')'  opt_interleave
 	| 'FOREIGN' 'KEY' '(' name_list ')' 'REFERENCES' table_name opt_column_list key_match reference_actions

pkg/sql/alter_table.go

@@ -163,6 +163,11 @@ func (n *alterTableNode) startExec(params runParams) error {
 		case *tree.AlterTableAddConstraint:
 			switch d := t.ConstraintDef.(type) {
 			case *tree.UniqueConstraintTableDef:
+				if d.NoIndex {
+					return pgerror.New(pgcode.FeatureNotSupported,
+						"unique constraints without an index are not yet supported",
+					)
+				}
 				if d.PrimaryKey {
 					// We only support "adding" a primary key when we are using the
 					// default rowid primary index or if a DROP PRIMARY KEY statement

pkg/sql/catalog/tabledesc/table.go

@@ -64,6 +64,11 @@ func MakeColumnDefDescs(
 		// Should never happen since `HoistConstraints` moves these to table level
 		return nil, nil, nil, errors.New("unexpected column REFERENCED constraint")
 	}
+	if d.UniqueNoIndex {
+		return nil, nil, nil, pgerror.New(pgcode.FeatureNotSupported,
+			"unique constraints without an index are not yet supported",
+		)
+	}
 
 	col := &descpb.ColumnDescriptor{
 		Name:     string(d.Name),
@@ -107,7 +112,7 @@ func MakeColumnDefDescs(
 	}
 
 	var idx *descpb.IndexDescriptor
-	if d.PrimaryKey.IsPrimaryKey || d.Unique {
+	if d.PrimaryKey.IsPrimaryKey || (d.Unique && !d.UniqueNoIndex) {
 		if !d.PrimaryKey.Sharded {
 			idx = &descpb.IndexDescriptor{
 				Unique:           true,

pkg/sql/create_table.go

@@ -1468,6 +1468,11 @@ func NewTableDesc(
 				return nil, unimplemented.NewWithIssue(9148, "use CREATE INDEX to make interleaved indexes")
 			}
 		case *tree.UniqueConstraintTableDef:
+			if d.NoIndex {
+				return nil, pgerror.New(pgcode.FeatureNotSupported,
+					"unique constraints without an index are not yet supported",
+				)
+			}
 			idx := descpb.IndexDescriptor{
 				Name:             string(d.Name),
 				Unique:           true,
@@ -2077,7 +2082,11 @@ func incTelemetryForNewColumn(def *tree.ColumnTableDef, desc *descpb.ColumnDescr
 		telemetry.Inc(sqltelemetry.SchemaNewColumnTypeQualificationCounter("default_expr"))
 	}
 	if def.Unique {
-		telemetry.Inc(sqltelemetry.SchemaNewColumnTypeQualificationCounter("unique"))
+		if def.UniqueNoIndex {
+			telemetry.Inc(sqltelemetry.SchemaNewColumnTypeQualificationCounter("unique_without_index"))
+		} else {
+			telemetry.Inc(sqltelemetry.SchemaNewColumnTypeQualificationCounter("unique"))
+		}
 	}
 }
 

pkg/sql/logictest/testdata/logic_test/alter_table

@@ -1401,3 +1401,17 @@ ALTER TABLE t_cannot_rename_constraint_over_index RENAME CONSTRAINT v_unique TO
 
 statement error relation idx_v already exists
 ALTER TABLE t_cannot_rename_constraint_over_index RENAME CONSTRAINT "primary" TO idx_v;
+
+subtest unique_without_index
+
+statement ok
+CREATE TABLE unique_without_index (
+  a INT,
+  b INT
+)
+
+statement error unique constraints without an index are not yet supported
+ALTER TABLE unique_without_index ADD COLUMN c INT UNIQUE WITHOUT INDEX
+
+statement error unique constraints without an index are not yet supported
+ALTER TABLE unique_without_index ADD CONSTRAINT ab UNIQUE WITHOUT INDEX (a, b)

pkg/sql/logictest/testdata/logic_test/create_table

@@ -316,3 +316,11 @@ CREATE TABLE error (LIKE like_hash_base INCLUDING STATISTICS)
 
 statement error unimplemented
 CREATE TABLE error (LIKE like_hash_base INCLUDING STORAGE)
+
+subtest unique_without_index
+
+statement error unique constraints without an index are not yet supported
+CREATE TABLE unique_without_index (a INT UNIQUE WITHOUT INDEX)
+
+statement error unique constraints without an index are not yet supported
+CREATE TABLE unique_without_index (a INT, b INT, CONSTRAINT ab UNIQUE WITHOUT INDEX (a, b))

pkg/sql/mutations/mutations.go

@@ -278,13 +278,15 @@ func statisticsMutator(
 					DistinctCount: distinctCount,
 					NullCount:     nullCount,
 				}
-				if def.Unique || def.PrimaryKey.IsPrimaryKey {
+				if (def.Unique && !def.UniqueNoIndex) || def.PrimaryKey.IsPrimaryKey {
 					makeHistogram(def)
 				}
 			case *tree.IndexTableDef:
 				makeHistogram(cols[def.Columns[0].Column])
 			case *tree.UniqueConstraintTableDef:
-				makeHistogram(cols[def.Columns[0].Column])
+				if !def.NoIndex {
+					makeHistogram(cols[def.Columns[0].Column])
+				}
 			}
 		}
 		if len(colStats) > 0 {
@@ -569,6 +571,10 @@ var postgresStatementMutator MultiStatementMutation = func(rng *rand.Rand, stmts
 						def.Family.Create = false
 						changed = true
 					}
+					if def.UniqueNoIndex {
+						def.UniqueNoIndex = false
+						changed = true
+					}
 				case *tree.UniqueConstraintTableDef:
 					if def.Interleave != nil {
 						def.Interleave = nil
@@ -578,6 +584,10 @@ var postgresStatementMutator MultiStatementMutation = func(rng *rand.Rand, stmts
 						def.PartitionBy = nil
 						changed = true
 					}
+					if def.NoIndex {
+						def.NoIndex = false
+						changed = true
+					}
 				}
 			}
 		case *tree.AlterTable:

pkg/sql/opt/testutils/testcat/create_table.go

@@ -18,6 +18,8 @@ import (
 	"github.com/cockroachdb/cockroach/pkg/geo/geoindex"
 	"github.com/cockroachdb/cockroach/pkg/sql/catalog/colinfo"
 	"github.com/cockroachdb/cockroach/pkg/sql/opt/cat"
+	"github.com/cockroachdb/cockroach/pkg/sql/pgwire/pgcode"
+	"github.com/cockroachdb/cockroach/pkg/sql/pgwire/pgerror"
 	"github.com/cockroachdb/cockroach/pkg/sql/sem/tree"
 	"github.com/cockroachdb/cockroach/pkg/sql/types"
 	"github.com/cockroachdb/cockroach/pkg/util"
@@ -178,6 +180,11 @@ func (tc *Catalog) CreateTable(stmt *tree.CreateTable) *Table {
 	for _, def := range stmt.Defs {
 		switch def := def.(type) {
 		case *tree.UniqueConstraintTableDef:
+			if def.NoIndex {
+				panic(pgerror.New(pgcode.FeatureNotSupported,
+					"unique constraints without an index are not yet supported",
+				))
+			}
 			if !def.PrimaryKey {
 				tab.addIndex(&def.IndexTableDef, uniqueIndex)
 			}
@@ -189,6 +196,11 @@ func (tc *Catalog) CreateTable(stmt *tree.CreateTable) *Table {
 			tab.addFamily(def)
 
 		case *tree.ColumnTableDef:
+			if def.UniqueNoIndex {
+				panic(pgerror.New(pgcode.FeatureNotSupported,
+					"unique constraints without an index are not yet supported",
+				))
+			}
 			if def.Unique {
 				tab.addIndex(
 					&tree.IndexTableDef{

pkg/sql/parser/parse_test.go

@@ -176,6 +176,7 @@ func TestParse(t *testing.T) {
 		{`CREATE TABLE a (b INT8 CONSTRAINT always NOT NULL)`},
 		{`CREATE TABLE a (b INT8 PRIMARY KEY)`},
 		{`CREATE TABLE a (b INT8 UNIQUE)`},
+		{`CREATE TABLE a (b INT8 UNIQUE WITHOUT INDEX)`},
 		{`CREATE TABLE a (b INT8 NULL PRIMARY KEY)`},
 		{`CREATE TABLE a (b INT8 DEFAULT 1)`},
 		{`CREATE TABLE a (b INT8 CONSTRAINT one DEFAULT 1)`},
@@ -223,6 +224,7 @@ func TestParse(t *testing.T) {
 		{`CREATE TABLE a (b INT8, c STRING, INDEX (b, c))`},
 		{`CREATE TABLE a (b INT8, c STRING, INDEX d (b, c))`},
 		{`CREATE TABLE a (b INT8, c STRING, CONSTRAINT d UNIQUE (b, c))`},
+		{`CREATE TABLE a (b INT8, c STRING, CONSTRAINT d UNIQUE WITHOUT INDEX (b, c))`},
 		{`CREATE TABLE a (b INT8, c STRING, CONSTRAINT d UNIQUE (b, c) INTERLEAVE IN PARENT d (e, f))`},
 		{`CREATE TABLE a (b INT8, UNIQUE (b))`},
 		{`CREATE TABLE a (b INT8, UNIQUE (b) STORING (c))`},
@@ -271,6 +273,7 @@ func TestParse(t *testing.T) {
 		{`CREATE TABLE a (b INT8 CONSTRAINT c PRIMARY KEY)`},
 		{`CREATE TABLE a (b INT8 CONSTRAINT c NULL)`},
 		{`CREATE TABLE a (b INT8 CONSTRAINT c UNIQUE)`},
+		{`CREATE TABLE a (b INT8 CONSTRAINT c UNIQUE WITHOUT INDEX)`},
 		{`CREATE TABLE a (b INT8 CONSTRAINT c DEFAULT d)`},
 		{`CREATE TABLE a (b INT8 CONSTRAINT c CHECK (d))`},
 		{`CREATE TABLE a (b INT8 CONSTRAINT c REFERENCES d)`},
@@ -1351,7 +1354,7 @@ func TestParse(t *testing.T) {
 		{`ALTER TABLE a ADD COLUMN IF NOT EXISTS b INT8, ADD CONSTRAINT a_idx UNIQUE (a)`},
 		{`ALTER TABLE IF EXISTS a ADD COLUMN b INT8, ADD CONSTRAINT a_idx UNIQUE (a)`},
 		{`ALTER TABLE IF EXISTS a ADD COLUMN IF NOT EXISTS b INT8, ADD CONSTRAINT a_idx UNIQUE (a)`},
-		{`ALTER TABLE a ADD COLUMN b INT8, ADD CONSTRAINT a_idx UNIQUE (a)`},
+		{`ALTER TABLE a ADD COLUMN b INT8 UNIQUE WITHOUT INDEX, ADD CONSTRAINT a_no_idx UNIQUE WITHOUT INDEX (a)`},
 		{`ALTER TABLE a ADD COLUMN IF NOT EXISTS b INT8, ADD CONSTRAINT a_idx UNIQUE (a) NOT VALID`},
 		{`ALTER TABLE IF EXISTS a ADD COLUMN b INT8, ADD CONSTRAINT a_idx UNIQUE (a)`},
 		{`ALTER TABLE IF EXISTS a ADD COLUMN IF NOT EXISTS b INT8, ADD CONSTRAINT a_idx UNIQUE (a)`},

pkg/sql/parser/sql.y

@@ -1020,7 +1020,7 @@ func (u *sqlSymUnion) refreshDataOption() tree.RefreshDataOption {
 %type <types.IntervalTypeMetadata> opt_interval_qualifier interval_qualifier interval_second
 %type <tree.Expr> overlay_placing
 
-%type <bool> opt_unique opt_concurrently opt_cluster
+%type <bool> opt_unique opt_concurrently opt_cluster opt_without_index
 %type <bool> opt_index_access_method
 
 %type <*tree.Limit> limit_clause offset_clause opt_limit_clause
@@ -1317,7 +1317,7 @@ alter_ddl_stmt:
 //   ALTER TABLE ... SET SCHEMA <newschemaname>
 //
 // Column qualifiers:
-//   [CONSTRAINT <constraintname>] {NULL | NOT NULL | UNIQUE | PRIMARY KEY | CHECK (<expr>) | DEFAULT <expr>}
+//   [CONSTRAINT <constraintname>] {NULL | NOT NULL | UNIQUE [WITHOUT INDEX] | PRIMARY KEY | CHECK (<expr>) | DEFAULT <expr>}
 //   FAMILY <familyname>, CREATE [IF NOT EXISTS] FAMILY [<familyname>]
 //   REFERENCES <tablename> [( <colnames...> )]
 //   COLLATE <collationname>
@@ -5426,11 +5426,11 @@ alter_schema_stmt:
 // Table constraints:
 //    PRIMARY KEY ( <colnames...> ) [USING HASH WITH BUCKET_COUNT = <shard_buckets>]
 //    FOREIGN KEY ( <colnames...> ) REFERENCES <tablename> [( <colnames...> )] [ON DELETE {NO ACTION | RESTRICT}] [ON UPDATE {NO ACTION | RESTRICT}]
-//    UNIQUE ( <colnames... ) [{STORING | INCLUDE | COVERING} ( <colnames...> )] [<interleave>]
+//    UNIQUE [WITHOUT INDEX] ( <colnames... ) [{STORING | INCLUDE | COVERING} ( <colnames...> )] [<interleave>]
 //    CHECK ( <expr> )
 //
 // Column qualifiers:
-//   [CONSTRAINT <constraintname>] {NULL | NOT NULL | UNIQUE | PRIMARY KEY | CHECK (<expr>) | DEFAULT <expr>}
+//   [CONSTRAINT <constraintname>] {NULL | NOT NULL | UNIQUE [WITHOUT INDEX] | PRIMARY KEY | CHECK (<expr>) | DEFAULT <expr>}
 //   FAMILY <familyname>, CREATE [IF NOT EXISTS] FAMILY [<familyname>]
 //   REFERENCES <tablename> [( <colnames...> )] [ON DELETE {NO ACTION | RESTRICT}] [ON UPDATE {NO ACTION | RESTRICT}]
 //   COLLATE <collationname>
@@ -5868,9 +5868,11 @@ col_qualification_elem:
   {
     $$.val = tree.NullConstraint{}
   }
-| UNIQUE
+| UNIQUE opt_without_index
   {
-    $$.val = tree.UniqueConstraint{}
+    $$.val = tree.UniqueConstraint{
+      NoIndex: $2.bool(),
+    }
   }
 | PRIMARY KEY
   {
@@ -5915,6 +5917,16 @@ col_qualification_elem:
     return 1
  }
 
+opt_without_index:
+  WITHOUT INDEX
+  {
+    $$.val = true
+  }
+| /* EMPTY */
+  {
+    $$.val = false
+  }
+
 // GENERATED ALWAYS is a noise word for compatibility with Postgres.
 generated_as:
   AS {}
@@ -5991,15 +6003,17 @@ constraint_elem:
       Expr: $3.expr(),
     }
   }
-| UNIQUE '(' index_params ')' opt_storing opt_interleave opt_partition_by opt_deferrable opt_where_clause
+| UNIQUE opt_without_index '(' index_params ')'
+    opt_storing opt_interleave opt_partition_by opt_deferrable opt_where_clause
   {
     $$.val = &tree.UniqueConstraintTableDef{
+      NoIndex: $2.bool(),
       IndexTableDef: tree.IndexTableDef{
-        Columns: $3.idxElems(),
-        Storing: $5.nameList(),
-        Interleave: $6.interleave(),
-        PartitionBy: $7.partitionBy(),
-        Predicate: $9.expr(),
+        Columns: $4.idxElems(),
+        Storing: $6.nameList(),
+        Interleave: $7.interleave(),
+        PartitionBy: $8.partitionBy(),
+        Predicate: $10.expr(),
       },
     }
   }

pkg/sql/rowenc/testutils.go

@@ -1368,7 +1368,7 @@ func IndexStoringMutator(rng *rand.Rand, stmts []tree.Statement) ([]tree.Stateme
 				case *tree.IndexTableDef:
 					idx = defType
 				case *tree.UniqueConstraintTableDef:
-					if !defType.PrimaryKey {
+					if !defType.PrimaryKey && !defType.NoIndex {
 						idx = &defType.IndexTableDef
 					}
 				}
@@ -1422,7 +1422,7 @@ func PartialIndexMutator(rng *rand.Rand, stmts []tree.Statement) ([]tree.Stateme
 				case *tree.IndexTableDef:
 					idx = defType
 				case *tree.UniqueConstraintTableDef:
-					if !defType.PrimaryKey {
+					if !defType.PrimaryKey && !defType.NoIndex {
 						idx = &defType.IndexTableDef
 					}
 				}