Function PQgetResult

src/interfaces/libpq/fe-exec.c:2016–2187

* PQgetResult * Get the next PGresult produced by a query. Returns NULL if no * query work remains or an error has occurred (e.g. out of * memory). * * In pipeline mode, once all the result of a query have been returned, * PQgetResult returns NULL to let the user know that the next * query is being processed. At the end of the pipeline, returns a * result with PQresultStatu

 *	  result with PQresultStatus(result) == PGRES_PIPELINE_SYNC.
 */
PGresult *
PQgetResult(PGconn *conn)
{
	PGresult   *res;

	if (!conn)
		return NULL;

	/* Parse any available data, if our state permits. */
	parseInput(conn);

	/* If not ready to return something, block until we are. */
	while (conn->asyncStatus == PGASYNC_BUSY)
	{
		int			flushResult;

		/*
		 * If data remains unsent, send it.  Else we might be waiting for the
		 * result of a command the backend hasn't even got yet.
		 */
		while ((flushResult = pqFlush(conn)) > 0)
		{
			if (pqWait(false, true, conn))
			{
				flushResult = -1;
				break;
			}
		}

		/*
		 * Wait for some more data, and load it.  (Note: if the connection has
		 * been lost, pqWait should return immediately because the socket
		 * should be read-ready, either with the last server data or with an
		 * EOF indication.  We expect therefore that this won't result in any
		 * undue delay in reporting a previous write failure.)
		 */
		if (flushResult ||
			pqWait(true, false, conn) ||
			pqReadData(conn) < 0)
		{
			/*
			 * conn->errorMessage has been set by pqWait or pqReadData. We
			 * want to append it to any already-received error message.
			 */
			pqSaveErrorResult(conn);
			conn->asyncStatus = PGASYNC_IDLE;
			return pqPrepareAsyncResult(conn);
		}

		/* Parse it. */
		parseInput(conn);

		/*
		 * If we had a write error, but nothing above obtained a query result
		 * or detected a read error, report the write error.
		 */
		if (conn->write_failed && conn->asyncStatus == PGASYNC_BUSY)
		{