Function DbStatsWorker

pg_documentdb/src/commands/db_stats.c:544–599

* This is the core logic for db_stats that executes on * every node in the cluster. */

 * every node in the cluster.
 */
static pgbson *
DbStatsWorker(void *fcinfoPointer)
{
	PG_FUNCTION_ARGS = fcinfoPointer;
	ArrayType *collectionIdArray = PG_GETARG_ARRAYTYPE_P(0);

	/* 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 (GetAllMongoCollectionShardOidsAndNamesInDB(collectionIdArray, &shardOids,
												   &shardNames))
	{
		Assert(shardNames != NULL);

		/*
		 * Given the relevant shard tables, get the total size of the overall table
		 * that is relevant to this node (sum up the table sizes across the shards
		 * located in this node).
		 */
		int64 totalRelationSize, totalTableSize;
		GetPostgresRelationSizes(shardOids, &totalRelationSize, &totalTableSize);

		/* Write it out to the target writer */
		PgbsonWriterAppendInt64(&writer, "total_rel_size", 14, totalRelationSize);
		PgbsonWriterAppendInt64(&writer, "total_tbl_size", 14, totalTableSize);

		/*
		 * Next get statistics details: Fetch document count from statistics
		 * We don't do runtime counts here - instead we do it in the coordinator
		 * if it's needed.
		 */
		int64 documentCount = GetPostgresDocumentCountStats(shardOids);

		PgbsonWriterAppendInt64(&writer, "total_doc_count", 15, documentCount);

		/*
		 * Look at statistics for document sizes.
		 */
		int32 workerAvgDocSize = GetAverageDocumentSizeFromStats(shardNames);
		PgbsonWriterAppendInt32(&writer, "avg_doc_size", 12, workerAvgDocSize);

		/*
		 * Get cumulative size of all indexes for given relationIds.
		 */
		int64 indexesSize = GetIndexSizesWorker(shardOids);
		PgbsonWriterAppendInt64(&writer, "indexes_size", 12, indexesSize);
	}

	return PgbsonWriterGetPgbson(&writer);
}