commit e71e84c9087098b65475e1441a26f0ee4aa93aae
Author: Alexander Korotkov <akorotkov@postgresql.org>
Date:   Sat Mar 30 18:11:29 2019 +0300

    Throw error in jsonb_path_match() when result is not single boolean
    
    jsonb_path_match() checks if jsonb document matches jsonpath query.  Therefore,
    jsonpath query should return single boolean.  Currently, if result of jsonpath
    is not a single boolean, NULL is returned independently whether silent mode
    is on or off.  But that appears to be wrong when silent mode is off.  This
    commit makes jsonb_path_match() throw an error in this case.
    
    Author: Nikita Glukhov

diff --git a/src/backend/utils/adt/jsonpath_exec.c b/src/backend/utils/adt/jsonpath_exec.c
index c07225749e5..074cea24ae3 100644
--- a/src/backend/utils/adt/jsonpath_exec.c
+++ b/src/backend/utils/adt/jsonpath_exec.c
@@ -320,7 +320,6 @@ jsonb_path_match(PG_FUNCTION_ARGS)
 {
 	Jsonb	   *jb = PG_GETARG_JSONB_P(0);
 	JsonPath   *jp = PG_GETARG_JSONPATH_P(1);
-	JsonbValue *jbv;
 	JsonValueList found = {0};
 	Jsonb	   *vars = NULL;
 	bool		silent = true;
@@ -333,18 +332,27 @@ jsonb_path_match(PG_FUNCTION_ARGS)
 
 	(void) executeJsonPath(jp, vars, jb, !silent, &found);
 
-	if (JsonValueListLength(&found) < 1)
-		PG_RETURN_NULL();
-
-	jbv = JsonValueListHead(&found);
-
 	PG_FREE_IF_COPY(jb, 0);
 	PG_FREE_IF_COPY(jp, 1);
 
-	if (jbv->type != jbvBool)
-		PG_RETURN_NULL();
+	if (JsonValueListLength(&found) == 1)
+	{
+		JsonbValue *jbv = JsonValueListHead(&found);
+
+		if (jbv->type == jbvBool)
+			PG_RETURN_BOOL(jbv->val.boolean);
+
+		if (jbv->type == jbvNull)
+			PG_RETURN_NULL();
+	}
+
+	if (!silent)
+		ereport(ERROR,
+				(errcode(ERRCODE_SINGLETON_JSON_ITEM_REQUIRED),
+				 errmsg(ERRMSG_SINGLETON_JSON_ITEM_REQUIRED),
+				 errdetail("expression should return a singleton boolean")));
 
-	PG_RETURN_BOOL(jbv->val.boolean);
+	PG_RETURN_NULL();
 }
 
 /*
diff --git a/src/test/regress/expected/jsonb_jsonpath.out b/src/test/regress/expected/jsonb_jsonpath.out
index 4a84d9157fa..49a857bca62 100644
--- a/src/test/regress/expected/jsonb_jsonpath.out
+++ b/src/test/regress/expected/jsonb_jsonpath.out
@@ -1769,6 +1769,57 @@ SELECT jsonb_path_exists('[{"a": 1}, {"a": 2}, {"a": 3}, {"a": 5}]', '$[*] ? (@.
  f
 (1 row)
 
+SELECT jsonb_path_match('true', '$', silent => false);
+ jsonb_path_match 
+------------------
+ t
+(1 row)
+
+SELECT jsonb_path_match('false', '$', silent => false);
+ jsonb_path_match 
+------------------
+ f
+(1 row)
+
+SELECT jsonb_path_match('null', '$', silent => false);
+ jsonb_path_match 
+------------------
+ 
+(1 row)
+
+SELECT jsonb_path_match('1', '$', silent => true);
+ jsonb_path_match 
+------------------
+ 
+(1 row)
+
+SELECT jsonb_path_match('1', '$', silent => false);
+ERROR:  singleton SQL/JSON item required
+DETAIL:  expression should return a singleton boolean
+SELECT jsonb_path_match('"a"', '$', silent => false);
+ERROR:  singleton SQL/JSON item required
+DETAIL:  expression should return a singleton boolean
+SELECT jsonb_path_match('{}', '$', silent => false);
+ERROR:  singleton SQL/JSON item required
+DETAIL:  expression should return a singleton boolean
+SELECT jsonb_path_match('[true]', '$', silent => false);
+ERROR:  singleton SQL/JSON item required
+DETAIL:  expression should return a singleton boolean
+SELECT jsonb_path_match('{}', 'lax $.a', silent => false);
+ERROR:  singleton SQL/JSON item required
+DETAIL:  expression should return a singleton boolean
+SELECT jsonb_path_match('{}', 'strict $.a', silent => false);
+ERROR:  SQL/JSON member not found
+DETAIL:  JSON object does not contain key "a"
+SELECT jsonb_path_match('{}', 'strict $.a', silent => true);
+ jsonb_path_match 
+------------------
+ 
+(1 row)
+
+SELECT jsonb_path_match('[true, true]', '$[*]', silent => false);
+ERROR:  singleton SQL/JSON item required
+DETAIL:  expression should return a singleton boolean
 SELECT jsonb '[{"a": 1}, {"a": 2}]' @@ '$[*].a > 1';
  ?column? 
 ----------
diff --git a/src/test/regress/sql/jsonb_jsonpath.sql b/src/test/regress/sql/jsonb_jsonpath.sql
index 28c861bb179..464ff94be37 100644
--- a/src/test/regress/sql/jsonb_jsonpath.sql
+++ b/src/test/regress/sql/jsonb_jsonpath.sql
@@ -366,6 +366,18 @@ SELECT jsonb_path_exists('[{"a": 1}, {"a": 2}]', '$[*].a ? (@ > 1)');
 SELECT jsonb_path_exists('[{"a": 1}, {"a": 2}, {"a": 3}, {"a": 5}]', '$[*] ? (@.a > $min && @.a < $max)', vars => '{"min": 1, "max": 4}');
 SELECT jsonb_path_exists('[{"a": 1}, {"a": 2}, {"a": 3}, {"a": 5}]', '$[*] ? (@.a > $min && @.a < $max)', vars => '{"min": 3, "max": 4}');
 
+SELECT jsonb_path_match('true', '$', silent => false);
+SELECT jsonb_path_match('false', '$', silent => false);
+SELECT jsonb_path_match('null', '$', silent => false);
+SELECT jsonb_path_match('1', '$', silent => true);
+SELECT jsonb_path_match('1', '$', silent => false);
+SELECT jsonb_path_match('"a"', '$', silent => false);
+SELECT jsonb_path_match('{}', '$', silent => false);
+SELECT jsonb_path_match('[true]', '$', silent => false);
+SELECT jsonb_path_match('{}', 'lax $.a', silent => false);
+SELECT jsonb_path_match('{}', 'strict $.a', silent => false);
+SELECT jsonb_path_match('{}', 'strict $.a', silent => true);
+SELECT jsonb_path_match('[true, true]', '$[*]', silent => false);
 SELECT jsonb '[{"a": 1}, {"a": 2}]' @@ '$[*].a > 1';
 SELECT jsonb '[{"a": 1}, {"a": 2}]' @@ '$[*].a > 2';
 SELECT jsonb_path_match('[{"a": 1}, {"a": 2}]', '$[*].a > 1');