Function DoSingleUpdateWithSubTxn

pg_documentdb/src/commands/update.c:1212–1275

* Updates a single update in a single sub-transaction. */

 * Updates a single update in a single sub-transaction.
 */
static bool
DoSingleUpdateWithSubTxn(MongoCollection *collection, UpdateSpec *updateSpec,
						 text *transactionId,
						 BatchUpdateResult *batchResult, int updateIndex, bool
						 forceInlineWrites,
						 ExprEvalState *volatile stateForSchemaValidation)
{
	/*
	 * Execute the query inside a sub-transaction, so we can restore order
	 * after a failure.
	 */
	MemoryContext oldContext = CurrentMemoryContext;
	ResourceOwner oldOwner = CurrentResourceOwner;

	/* declared volatile because of the longjmp in PG_CATCH */
	volatile bool isSuccess = false;

	UpdateResult updateResult;
	memset(&updateResult, 0, sizeof(updateResult));

	/* use a subtransaction to correctly handle failures */
	BeginInternalSubTransaction(NULL);

	PG_TRY();
	{
		ProcessUpdate(collection, updateSpec, transactionId, &updateResult,
					  forceInlineWrites, stateForSchemaValidation);

		/* Commit the inner transaction, return to outer xact context */
		ReleaseCurrentSubTransaction();
		MemoryContextSwitchTo(oldContext);
		CurrentResourceOwner = oldOwner;

		UpdateResultInBatch(batchResult, &updateResult,
							batchResult->resultMemoryContext, updateIndex);
		isSuccess = true;
	}
	PG_CATCH();
	{
		MemoryContextSwitchTo(oldContext);
		ErrorData *errorData = CopyErrorDataAndFlush();

		/* Abort the inner transaction */
		RollbackAndReleaseCurrentSubTransaction();
		MemoryContextSwitchTo(oldContext);
		CurrentResourceOwner = oldOwner;

		if (IsOperatorInterventionError(errorData))
		{
			ReThrowError(errorData);
		}

		MemoryContextSwitchTo(batchResult->resultMemoryContext);
		batchResult->writeErrors = lappend(batchResult->writeErrors,
										   GetWriteErrorFromErrorData(errorData,
																	  updateIndex));
		MemoryContextSwitchTo(oldContext);
		FreeErrorData(errorData);