diff options
Diffstat (limited to 'src/backend/commands/analyze.c')
| -rw-r--r-- | src/backend/commands/analyze.c | 19 |
1 files changed, 11 insertions, 8 deletions
diff --git a/src/backend/commands/analyze.c b/src/backend/commands/analyze.c index 268905aca94..bd66543f105 100644 --- a/src/backend/commands/analyze.c +++ b/src/backend/commands/analyze.c @@ -1194,19 +1194,22 @@ acquire_sample_rows(Relation onerel, int elevel, qsort((void *) rows, numrows, sizeof(HeapTuple), compare_rows); /* - * Estimate total numbers of rows in relation. For live rows, use - * vac_estimate_reltuples; for dead rows, we have no source of old - * information, so we have to assume the density is the same in unseen - * pages as in the pages we scanned. + * Estimate total numbers of live and dead rows in relation, extrapolating + * on the assumption that the average tuple density in pages we didn't + * scan is the same as in the pages we did scan. Since what we scanned is + * a random sample of the pages in the relation, this should be a good + * assumption. */ - *totalrows = vac_estimate_reltuples(onerel, true, - totalblocks, - bs.m, - liverows); if (bs.m > 0) + { + *totalrows = floor((liverows / bs.m) * totalblocks + 0.5); *totaldeadrows = floor((deadrows / bs.m) * totalblocks + 0.5); + } else + { + *totalrows = 0.0; *totaldeadrows = 0.0; + } /* * Emit some interesting relation info |