Function TryProcessOrIntoDollarIn

pg_documentdb/src/query/query_operator.c:4725–4844

static Expr *
TryProcessOrIntoDollarIn(BsonQueryOperatorContext *context,
						 List *orQuals)
{
	const MongoQueryOperator *op = GetMongoQueryOperatorByQueryOperatorType(
		QUERY_OPERATOR_EQ, context->inputType);

	/* First pass - validate all paths are the same and the $eq operator */
	StringView singlePath = { .length = 0, .string = "" };
	Expr *firstArg = NULL;
	ListCell *cell;
	pgbson_writer inValueWriter;
	PgbsonWriterInit(&inValueWriter);

	pgbson_element_writer elementWriter;
	PgbsonInitObjectElementWriter(&inValueWriter, &elementWriter, "", 0);

	pgbson_array_writer arrayWriter;
	PgbsonElementWriterStartArray(&elementWriter, &arrayWriter);
	foreach(cell, orQuals)
	{
		Expr *currentExpr = lfirst(cell);
		if (IsA(currentExpr, BoolExpr))
		{
			BoolExpr *boolExpr = (BoolExpr *) currentExpr;
			if (boolExpr->boolop == AND_EXPR &&
				list_length(boolExpr->args) == 1)
			{
				/* Flatten single $and */
				currentExpr = linitial(boolExpr->args);
			}
		}

		Oid funcId;
		List *args;
		if (IsA(currentExpr, FuncExpr))
		{
			FuncExpr *expr = (FuncExpr *) currentExpr;
			funcId = expr->funcid;
			args = expr->args;
		}
		else if (IsA(currentExpr, OpExpr))
		{
			OpExpr *opExpr = (OpExpr *) currentExpr;
			funcId = opExpr->opfuncid;
			args = opExpr->args;
		}
		else
		{
			return NULL;
		}

		/* Not a $eq - cannot convert to $in */
		if (funcId != op->postgresRuntimeFunctionOidLookup())
		{
			return NULL;
		}