3 files changed, 182 insertions, 7 deletions

diff --git a/src/backend/utils/adt/json.c b/src/backend/utils/adt/json.c
index dcd2bb2234a..49080e5fbff 100644
--- a/src/backend/utils/adt/json.c
+++ b/src/backend/utils/adt/json.c
@@ -62,6 +62,23 @@ typedef struct JsonUniqueHashEntry
 	int			object_id;
 } JsonUniqueHashEntry;
 
+/* Stack element for key uniqueness check during JSON parsing */
+typedef struct JsonUniqueStackEntry
+{
+	struct JsonUniqueStackEntry *parent;
+	int			object_id;
+} JsonUniqueStackEntry;
+
+/* Context struct for key uniqueness check during JSON parsing */
+typedef struct JsonUniqueParsingState
+{
+	JsonLexContext *lex;
+	JsonUniqueCheckState check;
+	JsonUniqueStackEntry *stack;
+	int			id_counter;
+	bool		unique;
+} JsonUniqueParsingState;
+
 /* Context struct for key uniqueness check during JSON building */
 typedef struct JsonUniqueBuilderState
 {
@@ -1648,6 +1665,110 @@ escape_json(StringInfo buf, const char *str)
 	appendStringInfoCharMacro(buf, '"');
 }
 
+/* Semantic actions for key uniqueness check */
+static JsonParseErrorType
+json_unique_object_start(void *_state)
+{
+	JsonUniqueParsingState *state = _state;
+	JsonUniqueStackEntry *entry;
+
+	if (!state->unique)
+		return JSON_SUCCESS;
+
+	/* push object entry to stack */
+	entry = palloc(sizeof(*entry));
+	entry->object_id = state->id_counter++;
+	entry->parent = state->stack;
+	state->stack = entry;
+
+	return JSON_SUCCESS;
+}
+
+static JsonParseErrorType
+json_unique_object_end(void *_state)
+{
+	JsonUniqueParsingState *state = _state;
+	JsonUniqueStackEntry *entry;
+
+	if (!state->unique)
+		return JSON_SUCCESS;
+
+	entry = state->stack;
+	state->stack = entry->parent;	/* pop object from stack */
+	pfree(entry);
+	return JSON_SUCCESS;
+}
+
+static JsonParseErrorType
+json_unique_object_field_start(void *_state, char *field, bool isnull)
+{
+	JsonUniqueParsingState *state = _state;
+	JsonUniqueStackEntry *entry;
+
+	if (!state->unique)
+		return JSON_SUCCESS;
+
+	/* find key collision in the current object */
+	if (json_unique_check_key(&state->check, field, state->stack->object_id))
+		return JSON_SUCCESS;
+
+	state->unique = false;
+
+	/* pop all objects entries */
+	while ((entry = state->stack))
+	{
+		state->stack = entry->parent;
+		pfree(entry);
+	}
+	return JSON_SUCCESS;
+}
+
+/* Validate JSON text and additionally check key uniqueness */
+bool
+json_validate(text *json, bool check_unique_keys, bool throw_error)
+{
+	JsonLexContext *lex = makeJsonLexContext(json, check_unique_keys);
+	JsonSemAction uniqueSemAction = {0};
+	JsonUniqueParsingState state;
+	JsonParseErrorType result;
+
+	if (check_unique_keys)
+	{
+		state.lex = lex;
+		state.stack = NULL;
+		state.id_counter = 0;
+		state.unique = true;
+		json_unique_check_init(&state.check);
+
+		uniqueSemAction.semstate = &state;
+		uniqueSemAction.object_start = json_unique_object_start;
+		uniqueSemAction.object_field_start = json_unique_object_field_start;
+		uniqueSemAction.object_end = json_unique_object_end;
+	}
+
+	result = pg_parse_json(lex, check_unique_keys ? &uniqueSemAction : &nullSemAction);
+
+	if (result != JSON_SUCCESS)
+	{
+		if (throw_error)
+			json_errsave_error(result, lex, NULL);
+
+		return false;			/* invalid json */
+	}
+
+	if (check_unique_keys && !state.unique)
+	{
+		if (throw_error)
+			ereport(ERROR,
+					(errcode(ERRCODE_DUPLICATE_JSON_OBJECT_KEY_VALUE),
+					 errmsg("duplicate JSON object key value")));
+
+		return false;			/* not unique keys */
+	}
+
+	return true;				/* ok */
+}
+
 /*
  * SQL function json_typeof(json) -> text
  *
@@ -1663,21 +1784,18 @@ escape_json(StringInfo buf, const char *str)
 Datum
 json_typeof(PG_FUNCTION_ARGS)
 {
-	text	   *json;
-
-	JsonLexContext *lex;
-	JsonTokenType tok;
+	text	   *json = PG_GETARG_TEXT_PP(0);
+	JsonLexContext *lex = makeJsonLexContext(json, false);
 	char	   *type;
+	JsonTokenType tok;
 	JsonParseErrorType result;
 
-	json = PG_GETARG_TEXT_PP(0);
-	lex = makeJsonLexContext(json, false);
-
 	/* Lex exactly one token from the input and check its type. */
 	result = json_lex(lex);
 	if (result != JSON_SUCCESS)
 		json_errsave_error(result, lex, NULL);
 	tok = lex->token_type;
+
 	switch (tok)
 	{
 		case JSON_TOKEN_OBJECT_START:
diff --git a/src/backend/utils/adt/jsonfuncs.c b/src/backend/utils/adt/jsonfuncs.c
index 7a36f74dad4..4c5abaff257 100644
--- a/src/backend/utils/adt/jsonfuncs.c
+++ b/src/backend/utils/adt/jsonfuncs.c
@@ -5665,3 +5665,23 @@ transform_string_values_scalar(void *state, char *token, JsonTokenType tokentype
 
 	return JSON_SUCCESS;
 }
+
+JsonTokenType
+json_get_first_token(text *json, bool throw_error)
+{
+	JsonLexContext *lex;
+	JsonParseErrorType result;
+
+	lex = makeJsonLexContext(json, false);
+
+	/* Lex exactly one token from the input and check its type. */
+	result = json_lex(lex);
+
+	if (result == JSON_SUCCESS)
+		return lex->token_type;
+
+	if (throw_error)
+		json_errsave_error(result, lex, NULL);
+
+	return JSON_TOKEN_INVALID;	/* invalid json */
+}
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 1c078d700d4..461735e84f0 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -8227,6 +8227,7 @@ isSimpleNode(Node *node, Node *parentNode, int prettyFlags)
 		case T_NullTest:
 		case T_BooleanTest:
 		case T_DistinctExpr:
+		case T_JsonIsPredicate:
 			switch (nodeTag(parentNode))
 			{
 				case T_FuncExpr:
@@ -9530,6 +9531,42 @@ get_rule_expr(Node *node, deparse_context *context,
 			get_json_constructor((JsonConstructorExpr *) node, context, false);
 			break;
 
+		case T_JsonIsPredicate:
+			{
+				JsonIsPredicate *pred = (JsonIsPredicate *) node;
+
+				if (!PRETTY_PAREN(context))
+					appendStringInfoChar(context->buf, '(');
+
+				get_rule_expr_paren(pred->expr, context, true, node);
+
+				appendStringInfoString(context->buf, " IS JSON");
+
+				/* TODO: handle FORMAT clause */
+
+				switch (pred->item_type)
+				{
+					case JS_TYPE_SCALAR:
+						appendStringInfoString(context->buf, " SCALAR");
+						break;
+					case JS_TYPE_ARRAY:
+						appendStringInfoString(context->buf, " ARRAY");
+						break;
+					case JS_TYPE_OBJECT:
+						appendStringInfoString(context->buf, " OBJECT");
+						break;
+					default:
+						break;
+				}
+
+				if (pred->unique_keys)
+					appendStringInfoString(context->buf, " WITH UNIQUE KEYS");
+
+				if (!PRETTY_PAREN(context))
+					appendStringInfoChar(context->buf, ')');
+			}
+			break;
+
 		case T_List:
 			{
 				char	   *sep;