Thread

[PATCH] Add sampling statistics to autoanalyze log output

Tatsuya Kawata <kawatatatsuya0913@gmail.com> — 2025-12-06T17:39:45Z

Hi,

I would like to propose a patch to add sampling statistics to autoanalyze
log output, addressing an inconsistency between ANALYZE VERBOSE and
autoanalyze logging.

## Problem

Currently, ANALYZE VERBOSE displays sampling statistics, but autoanalyze
does not log this information.
This makes it harder to diagnose issues with automatic statistics
collection.

Example (current behavior):
- ANALYZE VERBOSE: Shows "INFO:  "pg_class": scanned 14 of 14 pages,
containing 434 live rows and 11 dead rows; 434 rows in sample, 434
estimated total rows."
- autoanalyze: No sampling information

## Solution

This patch unifies the logging output by moving sampling statistics from
acquire_sample_rows() to do_analyze_rel()'s instrumentation section. Now
both ANALYZE VERBOSE and autoanalyze output the same sampling information
in a consolidated log message.

Key changes:
1. Updated AcquireSampleRowsFunc typedef to include 4 new output parameters
2. Modified acquire_sample_rows() and acquire_inherited_sample_rows() to
populate these parameters
3. Added sampling statistics output in do_analyze_rel()
4. Updated postgres_fdw and file_fdw implementations

## Example Output

After the patch(adding both ANALYZE VERBOSE and autoanalyze) :
sampling: scanned 14 of 14 pages, containing 434 live rows and 11 dead
rows; 434 rows in sample, 434 estimated total rows

For inherited tables, statistics are accumulated across all children.

## Design Question

For inherited tables, the current patch shows only the accumulated total.
An alternative approach would be to show per-child statistics followed by
the total.
I wanted to align with do_analyze_rel()'s structure to properly support
autoanalyze (autovacuum) logging.
However, I haven't found a clean way to preserve per-child output while
maintaining this structure.
I would appreciate any advice or suggestions on how to achieve both goals
if there's a better approach I'm missing.

I would appreciate your feedback!

Regards,