Check if access methods support an INCLUDE clause.

Trying to create an hypothetical index with an INCLUDE clause on pg10- will
obviously fail with a syntax error.

Also add regression test for the INCLUDE clause on btree indexes.

Makefile

@@ -44,7 +44,7 @@ ifeq ($(MAJORVERSION),10)
 endif
 
 ifneq ($(MAJORVERSION),$(filter $(MAJORVERSION), 9.2 9.3 9.4 9.5 9.6 10))
-	REGRESS += hypo_index_part
+	REGRESS += hypo_index_part hypo_include
 endif
 
 DEBUILD_ROOT = /tmp/$(EXTENSION)

expected/hypo_include.out

@@ -0,0 +1,55 @@
+-- hypothetical indexes using INCLUDE keyword, pg11+
+-- Remove all the hypothetical indexes if any
+SELECT hypopg_reset();
+ hypopg_reset 
+--------------
+ 
+(1 row)
+
+-- Make sure stats and visibility map are up to date
+VACUUM ANALYZE hypo;
+-- Should not use hypothetical index
+-- Create normal index
+SELECT hypopg_create_index('CREATE INDEX ON hypo (id)');
+     hypopg_create_index      
+------------------------------
+ (13719,<13719>btree_hypo_id)
+(1 row)
+
+-- Should use hypothetical index using a regular Index Scan
+SELECT COUNT(*) FROM do_explain('SELECT val FROM hypo WHERE id = 1') e
+WHERE e ~ 'Index Scan.*<\d+>btree_hypo.*';
+ count 
+-------
+     1
+(1 row)
+
+-- Remove all the hypothetical indexes
+SELECT hypopg_reset();
+ hypopg_reset 
+--------------
+ 
+(1 row)
+
+-- Create INCLUDE index
+SELECT hypopg_create_index('CREATE INDEX ON hypo (id) INCLUDE (val)');
+       hypopg_create_index        
+----------------------------------
+ (13719,<13719>btree_hypo_id_val)
+(1 row)
+
+-- Should use hypothetical index using an Index Only Scan
+SELECT COUNT(*) FROM do_explain('SELECT val FROM hypo WHERE id = 1') e
+WHERE e ~ 'Index Only Scan.*<\d+>btree_hypo.*';
+ count 
+-------
+     1
+(1 row)
+
+-- Deparse the index DDL
+SELECT hypopg_get_indexdef(indexrelid) FROM hypopg();
+                    hypopg_get_indexdef                     
+------------------------------------------------------------
+ CREATE INDEX ON public.hypo USING btree (id) INCLUDE (val)
+(1 row)
+

hypopg_index.c

@@ -173,6 +173,7 @@ hypo_newIndex(Oid relid, char *accessMethod, int nkeycolumns, int ninccolumns,
 	entry->amcanorder = amroutine->amcanorder;
 #if PG_VERSION_NUM >= 110000
 	entry->amcanparallel = amroutine->amcanparallel;
+	entry->amcaninclude = amroutine->amcaninclude;
 #endif
 #else
 	/* Up to 9.5, all information is available in the pg_am tuple */
@@ -443,6 +444,14 @@ hypo_index_store_parsetree(IndexStmt *node, const char *queryString)
 					 errmsg("hypopg: access method \"%s\" does not support multicolumn indexes",
 							node->accessMethod)));
 
+#if PG_VERSION_NUM >= 110000
+		if (node-> indexIncludingParams != NIL && !entry->amcaninclude)
+			ereport(ERROR,
+					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+					 errmsg("hypopg: access method \"%s\" does not support included columns",
+							node->accessMethod)));
+#endif
+
 		entry->unique = node->unique;
 		entry->ncolumns = nkeycolumns + ninccolumns;
 		entry->nkeycolumns = nkeycolumns;

include/hypopg_index.h

@@ -95,6 +95,8 @@ typedef struct hypoIndex
 	bool		amhasgetbitmap; /* does AM have amgetbitmap interface? */
 #if PG_VERSION_NUM >= 110000
 	bool		amcanparallel;	/* does AM support parallel scan? */
+	bool		amcaninclude;	/* does AM support columns included with clause
+								   INCLUDE? */
 #endif
 	bool		amcanunique;	/* does AM support UNIQUE indexes? */
 	bool		amcanmulticol;	/* does AM support multi-column indexes? */

test/sql/hypo_include.sql

@@ -0,0 +1,29 @@
+-- hypothetical indexes using INCLUDE keyword, pg11+
+
+-- Remove all the hypothetical indexes if any
+SELECT hypopg_reset();
+
+-- Make sure stats and visibility map are up to date
+VACUUM ANALYZE hypo;
+
+-- Should not use hypothetical index
+
+-- Create normal index
+SELECT hypopg_create_index('CREATE INDEX ON hypo (id)');
+
+-- Should use hypothetical index using a regular Index Scan
+SELECT COUNT(*) FROM do_explain('SELECT val FROM hypo WHERE id = 1') e
+WHERE e ~ 'Index Scan.*<\d+>btree_hypo.*';
+
+-- Remove all the hypothetical indexes
+SELECT hypopg_reset();
+
+-- Create INCLUDE index
+SELECT hypopg_create_index('CREATE INDEX ON hypo (id) INCLUDE (val)');
+
+-- Should use hypothetical index using an Index Only Scan
+SELECT COUNT(*) FROM do_explain('SELECT val FROM hypo WHERE id = 1') e
+WHERE e ~ 'Index Only Scan.*<\d+>btree_hypo.*';
+
+-- Deparse the index DDL
+SELECT hypopg_get_indexdef(indexrelid) FROM hypopg();