Get rid of recursion-marker values in enum AlterTableType

During ALTER TABLE execution, when prep-time handling of subcommands of
certain types determine that execution-time handling requires recursion,
they signal this by changing the subcommand type to a special value.
This can be done in a simpler way by using a separate flag introduced by
commit ec0925c22a3d, so do that.

Catversion bumped.  It's not clear to me that ALTER TABLE subcommands
are stored anywhere in catalogs (CREATE FUNCTION rejects it in BEGIN
ATOMIC function bodies), but we do have both write and read support for
them, so be safe.

Discussion: https://postgr.es/m/20220929090033.zxuaezcdwh2fgfjb@alvherre.pgsql

1 files changed, 13 insertions, 54 deletions

diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index ee88e87d76d..0b352a5fff6 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -4070,8 +4070,7 @@ AlterTableLookupRelation(AlterTableStmt *stmt, LOCKMODE lockmode)
  * For most subcommand types, phases 2 and 3 do no explicit recursion,
  * since phase 1 already does it.  However, for certain subcommand types
  * it is only possible to determine how to recurse at phase 2 time; for
- * those cases, phase 1 sets the cmd->recurse flag (or, in some older coding,
- * changes the command subtype of a "Recurse" variant XXX to be cleaned up.)
+ * those cases, phase 1 sets the cmd->recurse flag.
  *
  * Thanks to the magic of MVCC, an error anywhere along the way rolls back
  * the whole operation; we don't have to do anything special to clean up.
@@ -4276,7 +4275,6 @@ AlterTableGetLockLevel(List *cmds)
 				break;
 
 			case AT_AddConstraint:
-			case AT_AddConstraintRecurse:	/* becomes AT_AddConstraint */
 			case AT_ReAddConstraint:	/* becomes AT_AddConstraint */
 			case AT_ReAddDomainConstraint:	/* becomes AT_AddConstraint */
 				if (IsA(cmd->def, Constraint))
@@ -4628,7 +4626,7 @@ ATPrepCmd(List **wqueue, Relation rel, AlterTableCmd *cmd,
 			/* Recursion occurs during execution phase */
 			/* No command-specific prep needed except saving recurse flag */
 			if (recurse)
-				cmd->subtype = AT_AddConstraintRecurse;
+				cmd->recurse = true;
 			pass = AT_PASS_ADD_CONSTR;
 			break;
 		case AT_AddIndexConstraint: /* ADD CONSTRAINT USING INDEX */
@@ -4643,7 +4641,7 @@ ATPrepCmd(List **wqueue, Relation rel, AlterTableCmd *cmd,
 			/* Other recursion occurs during execution phase */
 			/* No command-specific prep needed except saving recurse flag */
 			if (recurse)
-				cmd->subtype = AT_DropConstraintRecurse;
+				cmd->recurse = true;
 			pass = AT_PASS_DROP;
 			break;
 		case AT_AlterColumnType:	/* ALTER COLUMN TYPE */
@@ -4765,7 +4763,7 @@ ATPrepCmd(List **wqueue, Relation rel, AlterTableCmd *cmd,
 			/* Recursion occurs during execution phase */
 			/* No command-specific prep needed except saving recurse flag */
 			if (recurse)
-				cmd->subtype = AT_ValidateConstraintRecurse;
+				cmd->recurse = true;
 			pass = AT_PASS_MISC;
 			break;
 		case AT_ReplicaIdentity:	/* REPLICA IDENTITY ... */
@@ -4930,12 +4928,7 @@ ATExecCmd(List **wqueue, AlteredTableInfo *tab,
 		case AT_AddColumn:		/* ADD COLUMN */
 		case AT_AddColumnToView:	/* add column via CREATE OR REPLACE VIEW */
 			address = ATExecAddColumn(wqueue, tab, rel, &cmd,
-									  false, false,
-									  lockmode, cur_pass, context);
-			break;
-		case AT_AddColumnRecurse:
-			address = ATExecAddColumn(wqueue, tab, rel, &cmd,
-									  true, false,
+									  cmd->recurse, false,
 									  lockmode, cur_pass, context);
 			break;
 		case AT_ColumnDefault:	/* ALTER COLUMN DEFAULT */
@@ -4989,13 +4982,7 @@ ATExecCmd(List **wqueue, AlteredTableInfo *tab,
 			break;
 		case AT_DropColumn:		/* DROP COLUMN */
 			address = ATExecDropColumn(wqueue, rel, cmd->name,
-									   cmd->behavior, false, false,
-									   cmd->missing_ok, lockmode,
-									   NULL);
-			break;
-		case AT_DropColumnRecurse:	/* DROP COLUMN with recursion */
-			address = ATExecDropColumn(wqueue, rel, cmd->name,
-									   cmd->behavior, true, false,
+									   cmd->behavior, cmd->recurse, false,
 									   cmd->missing_ok, lockmode,
 									   NULL);
 			break;
@@ -5015,27 +5002,14 @@ ATExecCmd(List **wqueue, AlteredTableInfo *tab,
 			/* Transform the command only during initial examination */
 			if (cur_pass == AT_PASS_ADD_CONSTR)
 				cmd = ATParseTransformCmd(wqueue, tab, rel, cmd,
-										  false, lockmode,
+										  cmd->recurse, lockmode,
 										  cur_pass, context);
 			/* Depending on constraint type, might be no more work to do now */
 			if (cmd != NULL)
 				address =
 					ATExecAddConstraint(wqueue, tab, rel,
 										(Constraint *) cmd->def,
-										false, false, lockmode);
-			break;
-		case AT_AddConstraintRecurse:	/* ADD CONSTRAINT with recursion */
-			/* Transform the command only during initial examination */
-			if (cur_pass == AT_PASS_ADD_CONSTR)
-				cmd = ATParseTransformCmd(wqueue, tab, rel, cmd,
-										  true, lockmode,
-										  cur_pass, context);
-			/* Depending on constraint type, might be no more work to do now */
-			if (cmd != NULL)
-				address =
-					ATExecAddConstraint(wqueue, tab, rel,
-										(Constraint *) cmd->def,
-										true, false, lockmode);
+										cmd->recurse, false, lockmode);
 			break;
 		case AT_ReAddConstraint:	/* Re-add pre-existing check constraint */
 			address =
@@ -5060,22 +5034,12 @@ ATExecCmd(List **wqueue, AlteredTableInfo *tab,
 			address = ATExecAlterConstraint(rel, cmd, false, false, lockmode);
 			break;
 		case AT_ValidateConstraint: /* VALIDATE CONSTRAINT */
-			address = ATExecValidateConstraint(wqueue, rel, cmd->name, false,
-											   false, lockmode);
-			break;
-		case AT_ValidateConstraintRecurse:	/* VALIDATE CONSTRAINT with
-											 * recursion */
-			address = ATExecValidateConstraint(wqueue, rel, cmd->name, true,
+			address = ATExecValidateConstraint(wqueue, rel, cmd->name, cmd->recurse,
 											   false, lockmode);
 			break;
 		case AT_DropConstraint: /* DROP CONSTRAINT */
 			ATExecDropConstraint(rel, cmd->name, cmd->behavior,
-								 false, false,
-								 cmd->missing_ok, lockmode);
-			break;
-		case AT_DropConstraintRecurse:	/* DROP CONSTRAINT with recursion */
-			ATExecDropConstraint(rel, cmd->name, cmd->behavior,
-								 true, false,
+								 cmd->recurse, false,
 								 cmd->missing_ok, lockmode);
 			break;
 		case AT_AlterColumnType:	/* ALTER COLUMN TYPE */
@@ -5351,7 +5315,7 @@ ATParseTransformCmd(List **wqueue, AlteredTableInfo *tab, Relation rel,
 			case AT_AddConstraint:
 				/* Recursion occurs during execution phase */
 				if (recurse)
-					cmd2->subtype = AT_AddConstraintRecurse;
+					cmd2->recurse = true;
 				switch (castNode(Constraint, cmd2->def)->contype)
 				{
 					case CONSTR_PRIMARY:
@@ -6110,7 +6074,6 @@ alter_table_type_to_string(AlterTableType cmdtype)
 	switch (cmdtype)
 	{
 		case AT_AddColumn:
-		case AT_AddColumnRecurse:
 		case AT_AddColumnToView:
 			return "ADD COLUMN";
 		case AT_ColumnDefault:
@@ -6135,13 +6098,11 @@ alter_table_type_to_string(AlterTableType cmdtype)
 		case AT_SetCompression:
 			return "ALTER COLUMN ... SET COMPRESSION";
 		case AT_DropColumn:
-		case AT_DropColumnRecurse:
 			return "DROP COLUMN";
 		case AT_AddIndex:
 		case AT_ReAddIndex:
 			return NULL;		/* not real grammar */
 		case AT_AddConstraint:
-		case AT_AddConstraintRecurse:
 		case AT_ReAddConstraint:
 		case AT_ReAddDomainConstraint:
 		case AT_AddIndexConstraint:
@@ -6149,10 +6110,8 @@ alter_table_type_to_string(AlterTableType cmdtype)
 		case AT_AlterConstraint:
 			return "ALTER CONSTRAINT";
 		case AT_ValidateConstraint:
-		case AT_ValidateConstraintRecurse:
 			return "VALIDATE CONSTRAINT";
 		case AT_DropConstraint:
-		case AT_DropConstraintRecurse:
 			return "DROP CONSTRAINT";
 		case AT_ReAddComment:
 			return NULL;		/* not real grammar */
@@ -6671,7 +6630,7 @@ ATPrepAddColumn(List **wqueue, Relation rel, bool recurse, bool recursing,
 		ATTypedTableRecursion(wqueue, rel, cmd, lockmode, context);
 
 	if (recurse && !is_view)
-		cmd->subtype = AT_AddColumnRecurse;
+		cmd->recurse = true;
 }
 
 /*
@@ -8376,7 +8335,7 @@ ATPrepDropColumn(List **wqueue, Relation rel, bool recurse, bool recursing,
 		ATTypedTableRecursion(wqueue, rel, cmd, lockmode, context);
 
 	if (recurse)
-		cmd->subtype = AT_DropColumnRecurse;
+		cmd->recurse = true;
 }
 
 /*