Function CancelIndexBuildRequest

pg_documentdb/src/commands/drop_indexes.c:990–1053

* CancelIndexBuildRequest cancels an existing (if there is any) running Index Build request for the indexId. */

 * CancelIndexBuildRequest cancels an existing (if there is any) running Index Build request for the indexId.
 */
static void
CancelIndexBuildRequest(int indexId)
{
	char *cancelIndexBuildRequestQueryStr = NULL;
	cancelIndexBuildRequestQueryStr = TryGetCancelIndexBuildQuery(indexId,
																  CREATE_INDEX_COMMAND_TYPE);
	if (cancelIndexBuildRequestQueryStr == NULL)
	{
		StringInfo cmdStr = makeStringInfo();
		appendStringInfo(cmdStr,
						 "SELECT iq.global_pid AS pid, iq.start_time AS timestamp");
		appendStringInfo(cmdStr,
						 " FROM %s iq WHERE index_id = %d",
						 GetIndexQueueName(), indexId);

		cancelIndexBuildRequestQueryStr = cmdStr->data;
	}

	bool readOnly = true;
	int numValues = 2;
	bool isNull[2];
	Datum results[2];
	ExtensionExecuteMultiValueQueryViaSPI(cancelIndexBuildRequestQueryStr, readOnly,
										  SPI_OK_SELECT, results,
										  isNull, numValues);

	if (!isNull[0])
	{
		StringInfo cancelCmdStr = makeStringInfo();
		Datum pid = results[0];
		Datum startTime = results[1];
		appendStringInfo(cancelCmdStr,
						 " SELECT pg_cancel_backend(pid) FROM pg_stat_activity ");
		appendStringInfo(cancelCmdStr, " WHERE pid = $1 AND query_start = $2");

		int nargs = 2;
		Oid argTypes[2] = { INT4OID, TIMESTAMPTZOID };
		Datum argValues[2] = {
			pid, startTime
		};

		const char **parameterValues = (const char **) palloc(nargs * sizeof(char *));

		/* TODO Now we also have a provision to cancel create index only when authenticated user is same as user who has submitted the create index request if(GetAuthenticatedUserId == user_oid)*/
		for (int i = 0; i < nargs; i++)
		{
			bool isVarlen;
			Oid funcOutOid;
			getTypeOutputInfo(argTypes[i], &funcOutOid, &isVarlen);
			parameterValues[i] = OidOutputFunctionCall(funcOutOid, argValues[i]);
		}

		/* Run pg_cancel_backend as super user via libpq otherwise we will not be able to cancel cron-job (launched as super user) */
		ExtensionExecuteQueryWithArgsAsUserOnLocalhostViaLibPQ(cancelCmdStr->data,
															   DocumentDBApiExtensionOwner(),
															   nargs, argTypes,
															   parameterValues);