Fix indexing of empty arrays and objects

Author: Nikita Glukhov

data/test_jsquery.data

@@ -1015,6 +1015,8 @@
 {"t": "a"}
 {"t": true}
 {"t": false}
+{}
+[]
 [1, 2, 3]
 ["a", "b", "c"]
 1

expected/jsquery.out

@@ -2631,13 +2631,13 @@ select count(*) from test_jsquery where v @@ '$ is numeric';
 select count(*) from test_jsquery where v @@ '$ is array';
  count 
 -------
-     2
+     3
 (1 row)
 
 select count(*) from test_jsquery where v @@ '$ is object';
  count 
 -------
-  1017
+  1018
 (1 row)
 
 select count(*) from test_jsquery where v @@ 'similar_product_ids.#: is numeric';
@@ -2655,7 +2655,7 @@ select count(*) from test_jsquery where v @@ 'similar_product_ids.#: is string';
 select count(*) from test_jsquery where v @@ 'NOT similar_product_ids.#: (NOT $ = "0440180295")';
  count 
 -------
-    40
+    42
 (1 row)
 
 select count(*) from test_jsquery where v @@ '$ > 2';
@@ -2679,7 +2679,7 @@ select count(*) from test_jsquery where v @@ 't';
 select count(*) from test_jsquery where v @@ '$';
  count 
 -------
-  1034
+  1036
 (1 row)
 
 select count(*) from test_jsquery where v @@ 'similar_product_ids.#';
@@ -2909,13 +2909,13 @@ select count(*) from test_jsquery where v @@ '$ is numeric';
 select count(*) from test_jsquery where v @@ '$ is array';
  count 
 -------
-     2
+     3
 (1 row)
 
 select count(*) from test_jsquery where v @@ '$ is object';
  count 
 -------
-  1017
+  1018
 (1 row)
 
 select count(*) from test_jsquery where v @@ 'similar_product_ids.#: is numeric';
@@ -2957,7 +2957,7 @@ select count(*) from test_jsquery where v @@ 't';
 select count(*) from test_jsquery where v @@ '$';
  count 
 -------
-  1034
+  1036
 (1 row)
 
 select count(*) from test_jsquery where v @@ 'similar_product_ids.#';
@@ -3232,13 +3232,13 @@ select count(*) from test_jsquery where v @@ '$ is numeric';
 select count(*) from test_jsquery where v @@ '$ is array';
  count 
 -------
-     2
+     3
 (1 row)
 
 select count(*) from test_jsquery where v @@ '$ is object';
  count 
 -------
-  1017
+  1018
 (1 row)
 
 select count(*) from test_jsquery where v @@ 'similar_product_ids.#: is numeric';
@@ -3280,7 +3280,7 @@ select count(*) from test_jsquery where v @@ 't';
 select count(*) from test_jsquery where v @@ '$';
  count 
 -------
-  1034
+  1036
 (1 row)
 
 select count(*) from test_jsquery where v @@ 'similar_product_ids.#';

jsonb_gin_ops.c

@@ -656,10 +656,7 @@ gin_extract_jsonb_value_path_internal(Jsonb *jb, int32 *nentries, uint32 **bloom
 	uint32		hash;
 
 	if (total == 0)
-	{
-		*nentries = 0;
-		return NULL;
-	}
+		total = 2;	/* single entry for empty object/array */
 
 	entries = (Datum *) palloc(sizeof(Datum) * total);
 	if (bloom)
@@ -1093,10 +1090,7 @@ gin_extract_jsonb_path_value_internal(Jsonb *jb, int32 *nentries)
 	Datum	   *entries = NULL;
 
 	if (total == 0)
-	{
-		*nentries = 0;
-		return NULL;
-	}
+		total = 2;	/* single entry for empty object/array */
 
 	entries = (Datum *) palloc(sizeof(Datum) * total);