Function SerializeTermToWriter

pg_documentdb/src/opclass/gin_index_term.c:1744–2017

* Serializes a given term to a pgbson writer honoring the truncation limits. * Returns whether the term was truncated or not. */

 * Returns whether the term was truncated or not.
 */
static bool
SerializeTermToWriter(pgbson_writer *writer, pgbsonelement *indexElement,
					  const IndexTermCreateMetadata *termMetadata,
					  bool allowValueOnly, bool *isValueOnly)
{
	/* Bson size + \0 overhead + path + \0 + type marker */
	StringView indexPath =
	{
		.length = indexElement->pathLength,
		.string = indexElement->path
	};

	char *newPath = NULL;

	if (termMetadata->pathPrefix.length > 0 && indexPath.length > 0 &&
		!termMetadata->isWildcard)
	{
		if (!StringViewEquals(&indexPath, &termMetadata->pathPrefix))
		{
			ereport(ERROR, (errcode(ERRCODE_DOCUMENTDB_INTERNALERROR),
							errmsg(
								"Wildcard Prefix path encountered with non-wildcard index - path %s, prefix %s",
								indexPath.string, termMetadata->pathPrefix.string)));
		}

		/* Index term should occupy a minimal amount of space */
		if (termMetadata->allowValueOnly && allowValueOnly)
		{
			indexPath.length = 0;
			indexPath.string = "";
			*isValueOnly = true;
		}
		else
		{
			indexPath.length = 1;
			indexPath.string = "$";
		}
	}
	else if (termMetadata->indexTermSizeLimit > 0 && termMetadata->isWildcard)
	{
		/* If it is a single path wildcard index with a non root projection we can trim down the key by removing the prefix. */
		if (!termMetadata->isWildcardProjection && termMetadata->pathPrefix.length > 0 &&
			indexPath.length > 0)
		{
			int32_t newIndexPathLength = indexPath.length -
										 termMetadata->pathPrefix.length;

			/* We only proceed with the optimization if the new index path length >= 0, otherwise we lose the root term */
			if (newIndexPathLength == 0)
			{
				indexPath.string = "$";
				indexPath.length = 1;
			}
			if (newIndexPathLength > 0)
			{
				newPath = palloc0(sizeof(char) * (newIndexPathLength + 2));

				/* Build the $.suffix string i.e if the pathPrefix is a.b.c.d.e.$** and the index element path is a.b.c.d.e.f.g we can transform to $.f.g */