Function bson_dollar_expr

pg_documentdb/src/query/bson_dollar_operators.c:1736–1797

* implements $expr functionality * in the runtime. Evaluates the expression pointed to by the filter * against the document. Returns true in the following cases: * 1) The expression evaluated to a boolean result and is true. * 2) The expression evaluated to a numeric and is not 0. * 3) The expression evaluated to a result that is defined. */

 * 3) The expression evaluated to a result that is defined.
 */
Datum
bson_dollar_expr(PG_FUNCTION_ARGS)
{
	pgbson *document = PG_GETARG_PGBSON(0);
	pgbson *filter = PG_GETARG_PGBSON(1);
	pgbson *variablesContext = NULL;

	int argPositions[2] = { 1, 2 };
	int numArgs = 1;

	if (PG_NARGS() > 2)
	{
		variablesContext = PG_GETARG_MAYBE_NULL_PGBSON(2);
		numArgs = 2;
	}

	const BsonDollarExprQueryState *cachedExprQueryState = NULL;
	BsonDollarExprQueryState localState = { 0 };
	SetCachedFunctionStateMultiArgs(
		cachedExprQueryState,
		BsonDollarExprQueryState,
		argPositions,
		numArgs,
		PopulateExprStateFromQuery,
		filter,
		variablesContext);

	if (cachedExprQueryState == NULL)
	{
		PopulateExprStateFromQuery(&localState, filter, variablesContext);
		cachedExprQueryState = &localState;
	}

	pgbson_writer writer;
	PgbsonWriterInit(&writer);
	bool isNullOnEmpty = false;
	StringView emptyPathView = { .length = 0, .string = "" };
	EvaluateAggregationExpressionDataToWriter(
		cachedExprQueryState->expression,
		document, emptyPathView, &writer,
		cachedExprQueryState->variableContext,
		isNullOnEmpty);

	bson_iter_t resultIterator;
	PgbsonWriterGetIterator(&writer, &resultIterator);

	if (!bson_iter_next(&resultIterator))
	{
		PG_RETURN_BOOL(false);
	}

	pgbsonelement resultElement;
	BsonIterToPgbsonElement(&resultIterator, &resultElement);
	if (BsonValueIsNumberOrBool(&resultElement.bsonValue))
	{
		PG_RETURN_BOOL(BsonValueAsInt32(&resultElement.bsonValue) != 0);
	}