Function QueryCtx_LockForCommit

src/query_ctx.c:345–390

starts a locking flow before commiting changes Locking flow: 1. lock GIL 2. open key with `write` flag 3. graph R/W lock with write flag since 2PL protocal is implemented, the method returns true if it managed to achieve locks in this call or a previous call in case that the locks are already locked, there will be no attempt to lock them again this method returns false if the key has changed from

// them again this method returns false if the key has changed
// from the current graph, and sets the relevant error message
bool QueryCtx_LockForCommit(void) {
	QueryCtx *ctx = _QueryCtx_GetCreateCtx();
	if(ctx->internal_exec_ctx.locked_for_commit) return true;

	// lock GIL
	RedisModuleCtx *redis_ctx = ctx->global_exec_ctx.redis_ctx;
	GraphContext *gc = ctx->gc;
	RedisModuleString *graphID = RedisModule_CreateString(redis_ctx, gc->graph_name,
														  strlen(gc->graph_name));
	_QueryCtx_ThreadSafeContextLock(ctx);

	// open key and verify
	RedisModuleKey *key = RedisModule_OpenKey(redis_ctx, graphID, REDISMODULE_WRITE);
	RedisModule_FreeString(redis_ctx, graphID);
	if(RedisModule_KeyType(key) == REDISMODULE_KEYTYPE_EMPTY) {
		ErrorCtx_SetError("Encountered an empty key when opened key %s", ctx->gc->graph_name);
		goto clean_up;
	}
	if(RedisModule_ModuleTypeGetType(key) != GraphContextRedisModuleType) {
		ErrorCtx_SetError("Encountered a non-graph value type when opened key %s", ctx->gc->graph_name);
		goto clean_up;

	}
	if(gc != RedisModule_ModuleTypeGetValue(key)) {
		ErrorCtx_SetError("Encountered different graph value when opened key %s", ctx->gc->graph_name);
		goto clean_up;
	}
	ctx->internal_exec_ctx.key = key;

	// acquire graph write lock
	Graph_AcquireWriteLock(gc->g);
	ctx->internal_exec_ctx.locked_for_commit = true;

	return true;

clean_up:
	// free key handle
	RedisModule_CloseKey(key);

	// unlock GIL
	_QueryCtx_ThreadSafeContextUnlock(ctx);

	// if there is a break point for runtime exception, raise it, otherwise return false
	ErrorCtx_RaiseRuntimeException(NULL);
	return false;
}

static void _QueryCtx_UnlockCommit
(