Function GetIndexBoundsForExplain

pg_documentdb/src/index_am/rum.c:1536–1588

static List *
GetIndexBoundsForExplain(Relation index_rel, Datum compositeArgDatum, bool hasOrderBy,
						 List **rawPerPathBounds)
{
	uint32_t nentries = 0;
	bool *partialMatch = NULL;
	Pointer *extraData = NULL;

	/* From the composite keys, get the lower bounds of the scans */
	/* Call extract_query to get the index details */
	int32_t ginScanType = hasOrderBy ? GIN_SEARCH_MODE_ALL :
						  GIN_SEARCH_MODE_DEFAULT;
	LOCAL_FCINFO(fcinfo, 7);
	fcinfo->flinfo = palloc(sizeof(FmgrInfo));
	fmgr_info_copy(fcinfo->flinfo,
				   index_getprocinfo(index_rel, 1,
									 GIN_EXTRACTQUERY_PROC),
				   CurrentMemoryContext);

	fcinfo->args[0].value = compositeArgDatum;
	fcinfo->args[1].value = PointerGetDatum(&nentries);
	fcinfo->args[2].value = Int16GetDatum(BSON_INDEX_STRATEGY_COMPOSITE_QUERY);
	fcinfo->args[3].value = PointerGetDatum(&partialMatch);
	fcinfo->args[4].value = PointerGetDatum(&extraData);
	fcinfo->args[6].value = PointerGetDatum(&ginScanType);

	Datum *entryRes = (Datum *) gin_bson_composite_path_extract_query(fcinfo);

	/* Now write out the result for explain */
	List *boundsList = NIL;
	for (uint32_t i = 0; i < nentries; i++)
	{
		bytea *entry = DatumGetByteaPP(entryRes[i]);

		if (IsSerializedRootTruncationTerm(entry))
		{
			continue;
		}

		List *rawPathBoundsInner = NIL;
		char *serializedBound = SerializeBoundsStringForExplain(entry,
																extraData[i],
																fcinfo,
																&rawPathBoundsInner);
		boundsList = lappend(boundsList, serializedBound);
		if (rawPathBoundsInner != NIL)
		{
			*rawPerPathBounds = list_concat(*rawPerPathBounds, rawPathBoundsInner);
		}
	}

	return boundsList;
}


static void