On Fri, Aug 23, 2024 at 10:26 AM Adrian Klaver <adrian.kla...@aklaver.com> wrote:
> On 8/23/24 09:14, Matthew Tice wrote: > > Hi All, > > > > I'm trying to understand why there's a difference between what > > pgstattuple reports and pg_stat_user_tables reports (for the number of > > dead tuples). > > > > As I understand, pgstattuple and pgstattuple_approx return the exact > > number of dead tuples (as noted in the documentation) and based on an > > https://www.postgresql.org/docs/current/pgstattuple.html > > pgstattuple_approx(regclass) returns record > > pgstattuple_approx is a faster alternative to pgstattuple that > returns approximate results. > > Not sure how you get exact count out of that? > Maybe the wording is a little confusing to me. Under the section for pgstattuple_approx: "pgstattuple_approx tries to avoid the full-table scan and returns exact dead tuple statistics along with an approximation of the number and size of live tuples and free space." > > > This is a Google Alloy DB instance running: > > https://cloud.google.com/alloydb/docs/overview > > "AlloyDB for PostgreSQL is a fully managed, PostgreSQL-compatible > database service that's designed for your most demanding workloads, > including hybrid transactional and analytical processing. AlloyDB pairs > a Google-built database engine with a cloud-based, multi-node > architecture to deliver enterprise-grade performance, reliability, and > availability." > > Where the important parts are 'PostgreSQL-compatible' and 'Google-built > database engine'. You probably need to reach out to Google to see what > that means for this situation. > > Got it, thanks Adrian. > > > > select version(); > > -[ RECORD 1 ]------------------------- > > version | PostgreSQL 14.10 on x86_64-pc-linux-gnu, compiled by Debian > > clang version 12.0.1, 64-bit > > SELECT 1 > > -- > Adrian Klaver > adrian.kla...@aklaver.com > >
