Add support for LIKE in CREATE FOREIGN TABLE

LIKE enables the creation of foreign tables based on the column
definitions, constraints and objects of the defined source relation(s).

This feature mirrors the behavior of CREATE TABLE LIKE, but ignores
the INCLUDING sub-options that do not make sense for foreign tables:
INDEXES, COMPRESSION, IDENTITY and STORAGE.  The supported sub-options
are COMMENTS, CONSTRAINTS, DEFAULTS, GENERATED and STATISTICS, mapping
with the clauses already supported by the command.

Note that the restriction with LIKE in CREATE FOREIGN TABLE was added in
a0c6dfeecfcc.

Author: Zhang Mingli
Reviewed-by: Álvaro Herrera, Sami Imseih, Michael Paquier
Discussion: https://postgr.es/m/42d3f855-2275-4361-a42a-826172ca2dc4@Spark

1 files changed, 13 insertions, 11 deletions

diff --git a/src/backend/parser/parse_utilcmd.c b/src/backend/parser/parse_utilcmd.c
index eb7716cd84c..abbe1bb45a3 100644
--- a/src/backend/parser/parse_utilcmd.c
+++ b/src/backend/parser/parse_utilcmd.c
@@ -1131,6 +1131,10 @@ transformTableConstraint(CreateStmtContext *cxt, Constraint *constraint)
  * 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.
+ *
+ * Some options are ignored.  For example, as foreign tables have no storage,
+ * these INCLUDING options have no effect: STORAGE, COMPRESSION, IDENTITY
+ * and INDEXES.  Similarly, INCLUDING INDEXES is ignored from a view.
  */
 static void
 transformTableLikeClause(CreateStmtContext *cxt, TableLikeClause *table_like_clause)
@@ -1145,12 +1149,6 @@ transformTableLikeClause(CreateStmtContext *cxt, TableLikeClause *table_like_cla
 	setup_parser_errposition_callback(&pcbstate, cxt->pstate,
 									  table_like_clause->relation->location);
 
-	/* we could support LIKE in many cases, but worry about it another day */
-	if (cxt->isforeign)
-		ereport(ERROR,
-				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-				 errmsg("LIKE is not supported for creating foreign tables")));
-
 	/* Open the relation referenced by the LIKE clause */
 	relation = relation_openrv(table_like_clause->relation, AccessShareLock);
 
@@ -1231,7 +1229,8 @@ transformTableLikeClause(CreateStmtContext *cxt, TableLikeClause *table_like_cla
 		 * Copy identity if requested
 		 */
 		if (attribute->attidentity &&
-			(table_like_clause->options & CREATE_TABLE_LIKE_IDENTITY))
+			(table_like_clause->options & CREATE_TABLE_LIKE_IDENTITY) &&
+			!cxt->isforeign)
 		{
 			Oid			seq_relid;
 			List	   *seq_options;
@@ -1250,14 +1249,16 @@ transformTableLikeClause(CreateStmtContext *cxt, TableLikeClause *table_like_cla
 		}
 
 		/* Likewise, copy storage if requested */
-		if (table_like_clause->options & CREATE_TABLE_LIKE_STORAGE)
+		if ((table_like_clause->options & CREATE_TABLE_LIKE_STORAGE) &&
+			!cxt->isforeign)
 			def->storage = attribute->attstorage;
 		else
 			def->storage = 0;
 
 		/* Likewise, copy compression if requested */
-		if ((table_like_clause->options & CREATE_TABLE_LIKE_COMPRESSION) != 0
-			&& CompressionMethodIsValid(attribute->attcompression))
+		if ((table_like_clause->options & CREATE_TABLE_LIKE_COMPRESSION) != 0 &&
+			CompressionMethodIsValid(attribute->attcompression) &&
+			!cxt->isforeign)
 			def->compression =
 				pstrdup(GetCompressionMethodName(attribute->attcompression));
 		else
@@ -1536,7 +1537,8 @@ expandTableLikeClause(RangeVar *heapRel, TableLikeClause *table_like_clause)
 	 * Process indexes if required.
 	 */
 	if ((table_like_clause->options & CREATE_TABLE_LIKE_INDEXES) &&
-		relation->rd_rel->relhasindex)
+		relation->rd_rel->relhasindex &&
+		childrel->rd_rel->relkind != RELKIND_FOREIGN_TABLE)
 	{
 		List	   *parent_indexes;
 		ListCell   *l;