Function IndexStatsWorker

pg_documentdb/src/aggregation/index_stats.c:125–276

* The core logic that queries each worker and gets the * index statistics. * The logic is simply to call pg_stat_all_indexes and get * the index accesses per index. */

 * the index accesses per index.
 */
static pgbson *
IndexStatsWorker(void *fcinfoPointer)
{
	PG_FUNCTION_ARGS = fcinfoPointer;
	Datum databaseName = PG_GETARG_DATUM(0);
	Datum collectionName = PG_GETARG_DATUM(1);

	MongoCollection *collection =
		GetMongoCollectionByNameDatum(databaseName,
									  collectionName,
									  AccessShareLock);

	if (collection == NULL)
	{
		ereport(ERROR, (errcode(ERRCODE_DOCUMENTDB_INVALIDNAMESPACE),
						errmsg("Collection '%s.%s' does not exist",
							   TextDatumGetCString(databaseName),
							   TextDatumGetCString(collectionName))));
	}

	/* First step, get the relevant shards on this node (We're already in the query worker) */
	ArrayType *shardNames = NULL;
	ArrayType *shardOids = NULL;

	/* Next get the relation and table size */
	pgbson_writer writer;
	PgbsonWriterInit(&writer);

	/* Only do work if there are shards */
	if (!GetMongoCollectionShardOidsAndNames(collection, &shardOids, &shardNames))
	{
		return PgbsonWriterGetPgbson(&writer);
	}

	Assert(shardNames != NULL);

	/*
	 * Walk the indexes for these shards and write out their sizes.
	 */
	pgbson_writer indexWriter;
	PgbsonWriterStartDocument(&writer, IndexUsageKey, -1, &indexWriter);

	const char *query =
		"SELECT indexrelid, idx_scan FROM pg_catalog.pg_stat_all_indexes "
		" WHERE relid =ANY ($1)";

	int nargs = 1;
	Oid argTypes[1] = { OIDARRAYOID };
	Datum argValues[1] = { PointerGetDatum(shardOids) };

	bool readOnly = true;
	MemoryContext priorMemoryContext = CurrentMemoryContext;

	HTAB *indexHash = CreatePgbsonElementHashSet();
	SPI_connect();

	Portal statsPortal = SPI_cursor_open_with_args("workerIndexUsageStats", query, nargs,
												   argTypes, argValues,