Fix failure with hypo index on unexisting table for pg10+.

expected/hypo_index.out

@@ -1,4 +1,8 @@
 -- Hypothetical index tests
+-- Hypothetical index on unexisting table
+SELECT COUNT(*) AS nb
+FROM public.hypopg_create_index('CREATE INDEX ON notatable(meh);');
+ERROR:  relation "notatable" does not exist
 CREATE TABLE hypo (id integer, val text);
 INSERT INTO hypo SELECT i, 'line ' || i
 FROM generate_series(1,100000) f(i);

hypopg_index.c

@@ -352,7 +352,12 @@ hypo_index_store_parsetree(IndexStmt *node, const char *queryString)
 		hypoTable  *table = hypo_table_name_get_entry(rv->relname);
 
 		if (!table)
-			elog(ERROR, "hypopg: table %s does not exists",
+			/*
+			 * We use the same error message as postgres so users (and
+			 * regression tests) get a consistent message error before and
+			 * after pg10.
+			 */
+			elog(ERROR, "relation \"%s\" does not exist",
 				 quote_identifier(rv->relname));
 
 		if (table->partkey)

hypopg_table.c

@@ -1920,15 +1920,18 @@ hypo_find_table(Oid tableid, bool missing_ok)
 }
 
 /*
- * Return the hypothetical oid if  the given name is an hypothetical partition,
- * otherwise return InvalidOid
+ * Return the hypothetical table if the given unqualified object name is an
+ * hypothetical partition, otherwise return NULL.
  */
 hypoTable *
 hypo_table_name_get_entry(const char *name)
 {
 	HASH_SEQ_STATUS hash_seq;
 	hypoTable  *entry;
 
+	if (!hypoTables)
+		return NULL;
+
 	hash_seq_init(&hash_seq, hypoTables);
 	while ((entry = hash_seq_search(&hash_seq)) != NULL)
 	{

test/sql/hypo_index.sql

@@ -1,5 +1,9 @@
 -- Hypothetical index tests
 
+-- Hypothetical index on unexisting table
+SELECT COUNT(*) AS nb
+FROM public.hypopg_create_index('CREATE INDEX ON notatable(meh);');
+
 CREATE TABLE hypo (id integer, val text);
 
 INSERT INTO hypo SELECT i, 'line ' || i