Function BuildRelationExtStatistics

src/backend/statistics/extended_stats.c:114–251

* Compute requested extended stats, using the rows sampled for the plain * (single-column) stats. * * This fetches a list of stats types from pg_statistic_ext, computes the * requested stats, and serializes them back into the catalog. */

 * requested stats, and serializes them back into the catalog.
 */
void
BuildRelationExtStatistics(Relation onerel, double totalrows,
						   int numrows, HeapTuple *rows,
						   int natts, VacAttrStats **vacattrstats)
{
	Relation	pg_stext;
	ListCell   *lc;
	List	   *statslist;
	MemoryContext cxt;
	MemoryContext oldcxt;
	int64		ext_cnt;

	/* Do nothing if there are no columns to analyze. */
	if (Gp_role == GP_ROLE_EXECUTE || !natts)
		return;

	/* the list of stats has to be allocated outside the memory context */
	pg_stext = table_open(StatisticExtRelationId, RowExclusiveLock);
	statslist = fetch_statentries_for_relation(pg_stext, RelationGetRelid(onerel));

	/* memory context for building each statistics object */
	cxt = AllocSetContextCreate(CurrentMemoryContext,
								"BuildRelationExtStatistics",
								ALLOCSET_DEFAULT_SIZES);
	oldcxt = MemoryContextSwitchTo(cxt);

	/* report this phase */
	if (statslist != NIL)
	{
		const int	index[] = {
			PROGRESS_ANALYZE_PHASE,
			PROGRESS_ANALYZE_EXT_STATS_TOTAL
		};
		const int64 val[] = {
			PROGRESS_ANALYZE_PHASE_COMPUTE_EXT_STATS,
			list_length(statslist)
		};

		pgstat_progress_update_multi_param(2, index, val);
	}

	ext_cnt = 0;
	foreach(lc, statslist)
	{
		StatExtEntry *stat = (StatExtEntry *) lfirst(lc);
		MVNDistinct *ndistinct = NULL;
		MVDependencies *dependencies = NULL;
		MCVList    *mcv = NULL;
		Datum		exprstats = (Datum) 0;
		VacAttrStats **stats;
		ListCell   *lc2;
		int			stattarget;
		StatsBuildData *data;

		/*
		 * Check if we can build these stats based on the column analyzed. If
		 * not, report this fact (except in autovacuum) and move on.
		 */