Further fixes for CREATE TABLE LIKE: cope with self-referential FKs.

Commit 502898192 was too careless about the order of execution of the
additional ALTER TABLE operations generated by expandTableLikeClause.
It just stuck them all at the end, which seems okay for most purposes.
But it falls down in the case where LIKE is importing a primary key
or unique index and the outer CREATE TABLE includes a FOREIGN KEY
constraint that needs to depend on that index.  Weird as that is,
it used to work, so we ought to keep it working.

To fix, make parse_utilcmd.c insert LIKE clauses between index-creation
and FK-creation commands in the transformed list of commands, and change
utility.c so that the commands generated by expandTableLikeClause are
executed immediately not at the end.  One could imagine scenarios where
this wouldn't work either; but currently expandTableLikeClause only
makes column default expressions, CHECK constraints, and indexes, and
this ordering seems fine for those.

Per bug #16730 from Sofoklis Papasofokli.  Like the previous patch,
back-patch to all supported branches.

Discussion: https://postgr.es/m/16730-b902f7e6e0276b30@postgresql.org

1 files changed, 22 insertions, 5 deletions

diff --git a/src/backend/parser/parse_utilcmd.c b/src/backend/parser/parse_utilcmd.c
index 254c0f65c2b..c709abad2b0 100644
--- a/src/backend/parser/parse_utilcmd.c
+++ b/src/backend/parser/parse_utilcmd.c
@@ -86,6 +86,7 @@ typedef struct
 	List	   *ckconstraints;	/* CHECK constraints */
 	List	   *fkconstraints;	/* FOREIGN KEY constraints */
 	List	   *ixconstraints;	/* index-creating constraints */
+	List	   *likeclauses;	/* LIKE clauses that need post-processing */
 	List	   *extstats;		/* cloned extended statistics */
 	List	   *blist;			/* "before list" of things to do before
 								 * creating the table */
@@ -243,6 +244,7 @@ transformCreateStmt(CreateStmt *stmt, const char *queryString)
 	cxt.ckconstraints = NIL;
 	cxt.fkconstraints = NIL;
 	cxt.ixconstraints = NIL;
+	cxt.likeclauses = NIL;
 	cxt.extstats = NIL;
 	cxt.blist = NIL;
 	cxt.alist = NIL;
@@ -310,6 +312,20 @@ transformCreateStmt(CreateStmt *stmt, const char *queryString)
 	transformIndexConstraints(&cxt);
 
 	/*
+	 * Re-consideration of LIKE clauses should happen after creation of
+	 * indexes, but before creation of foreign keys.  This order is critical
+	 * because a LIKE clause may attempt to create a primary key.  If there's
+	 * also a pkey in the main CREATE TABLE list, creation of that will not
+	 * check for a duplicate at runtime (since index_check_primary_key()
+	 * expects that we rejected dups here).  Creation of the LIKE-generated
+	 * pkey behaves like ALTER TABLE ADD, so it will check, but obviously that
+	 * only works if it happens second.  On the other hand, we want to make
+	 * pkeys before foreign key constraints, in case the user tries to make a
+	 * self-referential FK.
+	 */
+	cxt.alist = list_concat(cxt.alist, cxt.likeclauses);
+
+	/*
 	 * Postprocess foreign-key constraints.
 	 */
 	transformFKConstraints(&cxt, true, false);
@@ -923,7 +939,7 @@ transformTableConstraint(CreateStmtContext *cxt, Constraint *constraint)
  * Change the LIKE <srctable> portion of a CREATE TABLE statement into
  * column definitions that recreate the user defined column portions of
  * <srctable>.  Also, if there are any LIKE options that we can't fully
- * process at this point, add the TableLikeClause to cxt->alist, which
+ * process at this point, add the TableLikeClause to cxt->likeclauses, which
  * will cause utility.c to call expandTableLikeClause() after the new
  * table has been created.
  */
@@ -1088,15 +1104,15 @@ transformTableLikeClause(CreateStmtContext *cxt, TableLikeClause *table_like_cla
 	 * We cannot yet deal with defaults, CHECK constraints, or indexes, since
 	 * we don't yet know what column numbers the copied columns will have in
 	 * the finished table.  If any of those options are specified, add the
-	 * LIKE clause to cxt->alist so that expandTableLikeClause will be called
-	 * after we do know that.
+	 * LIKE clause to cxt->likeclauses so that expandTableLikeClause will be
+	 * called after we do know that.
 	 */
 	if (table_like_clause->options &
 		(CREATE_TABLE_LIKE_DEFAULTS |
 		 CREATE_TABLE_LIKE_GENERATED |
 		 CREATE_TABLE_LIKE_CONSTRAINTS |
 		 CREATE_TABLE_LIKE_INDEXES))
-		cxt->alist = lappend(cxt->alist, table_like_clause);
+		cxt->likeclauses = lappend(cxt->likeclauses, table_like_clause);
 
 	/*
 	 * We may copy extended statistics if requested, since the representation
@@ -2692,7 +2708,7 @@ transformFKConstraints(CreateStmtContext *cxt,
 	 * Note: the ADD CONSTRAINT command must also execute after any index
 	 * creation commands.  Thus, this should run after
 	 * transformIndexConstraints, so that the CREATE INDEX commands are
-	 * already in cxt->alist.
+	 * already in cxt->alist.  See also the handling of cxt->likeclauses.
 	 */
 	if (!isAddConstraint)
 	{
@@ -3205,6 +3221,7 @@ transformAlterTableStmt(Oid relid, AlterTableStmt *stmt,
 	cxt.ckconstraints = NIL;
 	cxt.fkconstraints = NIL;
 	cxt.ixconstraints = NIL;
+	cxt.likeclauses = NIL;
 	cxt.extstats = NIL;
 	cxt.blist = NIL;
 	cxt.alist = NIL;