Function IndexKeyDocumentEquivalent

pg_documentdb/src/metadata/index.c:2507–2586

* Checks if Index keys are equivalent. The keys are equal if everything * matches. They are equivalent if one index key can be treated as the same * index key to another index even if it's not an exact match (e.g. text indexes). * Otherwise, the keys are not equal. */

 * Otherwise, the keys are not equal.
 */
static IndexOptionsEquivalency
IndexKeyDocumentEquivalent(pgbson *leftKey, pgbson *rightKey)
{
	if (PgbsonEquals(leftKey, rightKey))
	{
		return IndexOptionsEquivalency_Equal;
	}

	/*
	 * Here we check for multiple things:
	 * If left or right has at least one text index, they're automatically equivalent.
	 * Are the keys/values unequal - then not equivalent
	 * If count(left keys) != count(right keys) then not equivalent.
	 */
	bool leftHasTextIndexes = false;
	bool rightHasTextIndexes = false;
	bool areEqual = true;

	/* The equivalency matters for text indexes */
	bson_iter_t leftIter;
	bson_iter_t rightIter;
	PgbsonInitIterator(leftKey, &leftIter);
	PgbsonInitIterator(rightKey, &rightIter);
	bool leftHasNext = bson_iter_next(&leftIter);
	bool rightHasNext = bson_iter_next(&rightIter);

	while (leftHasNext && rightHasNext)
	{
		if (areEqual && strcmp(bson_iter_key(&leftIter), bson_iter_key(&rightIter)) != 0)
		{
			areEqual = false;
		}

		const bson_value_t *leftValue = bson_iter_value(&leftIter);
		const bson_value_t *rightValue = bson_iter_value(&rightIter);

		if (areEqual && !BsonValueEquals(leftValue, rightValue))
		{
			areEqual = false;
		}

		leftHasTextIndexes = leftHasTextIndexes || IsTextIndex(leftValue);
		rightHasTextIndexes = rightHasTextIndexes || IsTextIndex(rightValue);

		leftHasNext = bson_iter_next(&leftIter);
		rightHasNext = bson_iter_next(&rightIter);
	}

	while (leftHasNext)
	{
		areEqual = false;
		const bson_value_t *leftValue = bson_iter_value(&leftIter);
		leftHasTextIndexes = leftHasTextIndexes || IsTextIndex(leftValue);
		leftHasNext = bson_iter_next(&leftIter);
	}

	while (rightHasNext)
	{