Add variable-length JsonContainer data

Nikita Glukhov · Nikita Glukhov · commit c30f00189bfb · 2022-07-27T00:46:13.000+03:00
diff --git a/src/backend/utils/adt/json_generic.c b/src/backend/utils/adt/json_generic.c
@@ -77,9 +77,9 @@ JsonInit(Json *json)
 	const void *data = DatumGetPointer(json->obj.value);
 	struct varlena *detoasted_data;
 
-	Assert(json->root.data || data);
+	Assert(JsonContainerDataPtr(&json->root) || data);
 
-	if (json->root.data || !data)
+	if (JsonContainerDataPtr(&json->root) || !data) /* FIXME */
 		return;
 
 	detoasted_data = PG_DETOAST_DATUM(json->obj.value);
@@ -92,18 +92,19 @@ JsonInit(Json *json)
 static Json *
 JsonExpand(Json *tmp, Datum value, bool freeValue, JsonContainerOps *ops)
 {
-	Json		   *json = tmp ? tmp : (Json *) palloc(sizeof(Json));
+	Json		   *json = tmp ? tmp : (Json *) palloc(JsonAllocSize(ops->data_size));
 
 	json->obj.value = value;
 	json->obj.freeValue = freeValue;
 	json->obj.isTemporary = tmp != NULL;
-	json->root.data = NULL;
 	json->root.len = 0;
 	json->root.ops = ops;
 	json->root.size = -1;
 	json->root.type = jbvBinary;
 	json->is_json = false;
 
+	memset(json->root._data, 0, ops->data_size);
+
 	return json;
 }
 
@@ -148,6 +149,8 @@ JsonValueToJson(JsonValue *val)
 									  jc->ops);
 
 		json->root = *jc;
+		memcpy(json->root._data, jc->_data, jc->ops->data_size);
+
 		return json;
 	}
 	else
@@ -161,11 +164,11 @@ JsonValueToJson(JsonValue *val)
 JsonContainer *
 JsonCopyFlat(JsonContainer *jc)
 {
-	JsonContainerData *res = JsonContainerAlloc();
+	JsonContainerData *res = JsonContainerAlloc(jc->ops);
 
 	*res = *jc;
-	res->data = palloc(jc->len);
-	memcpy(res->data, jc->data, jc->len);
+	JsonContainerDataPtr(res) = palloc(jc->len);
+	memcpy(JsonContainerDataPtr(res), JsonContainerDataPtr(jc), jc->len);
 
 	return res;
 }
diff --git a/src/backend/utils/adt/jsonb_util.c b/src/backend/utils/adt/jsonb_util.c
@@ -123,10 +123,12 @@ JsonContainerFlatten(JsonContainer *jc, JsonValueEncoder encoder,
 
 	if (jc->ops == ops)
 	{
-		int		size = jc->len;
-		void   *out = palloc(VARHDRSZ + size);
+		int			size = jc->len;
+		void       *out = palloc(VARHDRSZ + size);
+
 		SET_VARSIZE(out, VARHDRSZ + size);
-		memcpy(VARDATA(out), jc->data, size);
+		memcpy(VARDATA(out), JsonContainerDataPtr(jc), size);
+
 		return out;
 	}
 
@@ -429,7 +431,7 @@ JsonbArrayIteratorGetIth(JsonbArrayIterator *it, uint32 i)
 static JsonbValue *
 jsonbFindValueInArray(JsonContainer *jsc, const JsonbValue *key)
 {
-	const JsonbContainerHeader *container = jsc->data;
+	const JsonbContainerHeader *container = JsonContainerDataPtr(jsc);
 	JsonbArrayIterator	it;
 	JsonbValue		   *result = palloc(sizeof(JsonbValue));
 
@@ -508,7 +510,7 @@ static JsonbValue *
 jsonbFindKeyInObject(JsonContainer *jsc, const char *keyVal, int keyLen,
 					 JsonValue *res)
 {
-	const JsonbContainerHeader *container = jsc->data;
+	const JsonbContainerHeader *container = JsonContainerDataPtr(jsc);
 	const JEntry *children = container->children;
 	int			count = JsonContainerSize(jsc);
 	char	   *baseAddr;
@@ -583,7 +585,7 @@ jsonbGetArrayElement(JsonContainer *jsc, uint32 i)
 	if (!JsonContainerIsArray(jsc))
 		elog(ERROR, "not a jsonb array");
 
-	JsonbArrayIteratorInit(&it, jsc->data);
+	JsonbArrayIteratorInit(&it, JsonContainerDataPtr(jsc));
 
 	return JsonbArrayIteratorGetIth(&it, i);
 }
@@ -637,7 +639,7 @@ fillJsonbValue(const JsonbContainerHeader *container, int index,
 	{
 		Assert(JBE_ISCONTAINER(entry));
 		result->type = jbvBinary;
-		result->val.binary.data = JsonContainerAlloc();
+		result->val.binary.data = JsonContainerAlloc(&jsonbContainerOps);
 		jsonbInitContainer((JsonContainerData *) result->val.binary.data,
 				/* Remove alignment padding from data pointer and length */
 						   (JsonbContainerHeader *)(base_addr + INTALIGN(offset)),
@@ -1199,7 +1201,7 @@ iteratorFromContainer(JsonContainer *container, jsonbIterator *parent)
 static JsonIterator *
 jsonbIteratorInit(JsonContainer *cont)
 {
-	const JsonbContainerHeader *container = cont->data;
+	const JsonbContainerHeader *container = JsonContainerDataPtr(cont);
 	jsonbIterator *it;
 
 	it = palloc0(sizeof(jsonbIterator));
@@ -2069,7 +2071,7 @@ convertJsonbBinary(StringInfo buffer, JEntry *pheader, const JsonbValue *val,
 	{
 		int base_offset = buffer->len;
 		padBufferToInt(buffer);
-		appendToBuffer(buffer, jc->data, jc->len);
+		appendToBuffer(buffer, JsonContainerDataPtr(jc), jc->len);
 		*pheader = JENTRY_ISCONTAINER | (buffer->len - base_offset);
 	}
 	else
@@ -2201,12 +2203,11 @@ uniqueifyJsonbObject(JsonbValue *object, bool unique_keys, bool skip_nulls)
 	}
 }
 
-
 static void
 jsonbInitContainer(JsonContainerData *jc, JsonbContainerHeader *jbc, int len)
 {
 	jc->ops = &jsonbContainerOps;
-	jc->data = jbc;
+	JsonContainerDataPtr(jc) = jbc;
 	jc->len = len;
 	jc->size = jbc->header & JBC_CMASK;
 	jc->type = jbc->header & JBC_FOBJECT ? jbvObject :
@@ -2224,6 +2225,7 @@ jsonbInit(JsonContainerData *jc, Datum value)
 JsonContainerOps
 jsonbContainerOps =
 {
+	sizeof(JsonbContainerHeader *),
 	jsonbInit,
 	jsonbIteratorInit,
 	jsonbFindKeyInObject,
diff --git a/src/backend/utils/adt/jsonpath_exec.c b/src/backend/utils/adt/jsonpath_exec.c
@@ -2049,7 +2049,8 @@ executeKeyValueMethod(JsonPathExecContext *cxt, JsonPathItem *jsp,
 
 	/* construct object id from its base object and offset inside that */
 	id = jb->type != jbvBinary ? 0 :
-		(int64) ((char *) jbc->data - (char *) cxt->baseObject.jbc->data);	/* FIXME */
+		(int64) ((char *) JsonContainerDataPtr(jbc) -
+				 (char *) JsonContainerDataPtr(cxt->baseObject.jbc));	/* FIXME */
 	id += (int64) cxt->baseObject.id * INT64CONST(10000000000);
 
 	idval.type = jbvNumeric;
diff --git a/src/include/utils/json_generic.h b/src/include/utils/json_generic.h
@@ -26,10 +26,10 @@ typedef struct JsonContainerOps JsonContainerOps;
 typedef struct JsonContainerData
 {
 	JsonContainerOps   *ops;
-	void			   *data;
 	int					len;
 	int					size;
 	JsonbValueType		type;
+	void			   *_data[FLEXIBLE_ARRAY_MEMBER];
 } JsonContainerData;
 
 typedef const JsonContainerData JsonContainer;
@@ -49,6 +49,7 @@ struct JsonIteratorData
 
 struct JsonContainerOps
 {
+	int				data_size;
 	void			(*init)(JsonContainerData *jc, Datum value);
 	JsonIterator   *(*iteratorInit)(JsonContainer *jc);
 	JsonValue	   *(*findKeyInObject)(JsonContainer *object,
@@ -73,13 +74,14 @@ typedef struct CompressedObject
 typedef struct Json
 {
 	CompressedObject obj;
-	JsonContainerData root;
 	bool		is_json;		/* json or jsonb */
+	JsonContainerData root;
 } Json;
 
 typedef Json Jsonb;
 typedef JsonContainer JsonbContainer;
 
+#define JsonContainerDataPtr(jc)	((jc)->_data[0])
 
 #define JsonIsTemporary(json)		((json)->obj.isTemporary)
 
@@ -189,8 +191,14 @@ extern Json *DatumGetJson(Datum val, JsonContainerOps *ops, Json *tmp);
 extern void JsonFree(Json *json);
 extern Json *JsonCopyTemporary(Json *tmp);
 
-#define JsonContainerAlloc() \
-	((JsonContainerData *) palloc(sizeof(JsonContainerData)))
+#define JsonAllocSize(data_size) \
+	(offsetof(Json, root._data) + (data_size))
+
+#define JsonContainerAllocSize(data_size) \
+	(offsetof(JsonContainerData, _data) + (data_size))
+
+#define JsonContainerAlloc(ops) \
+	((JsonContainerData *) palloc(JsonContainerAllocSize((ops)->data_size)))
 
 extern JsonValue *JsonFindValueInContainer(JsonContainer *json, uint32 flags,
 										   JsonValue *key);
