Add Postgres support for like-for-like benchmark comparisons#3
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MrLukeSmith wants to merge 20 commits into
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Add Postgres support for like-for-like benchmark comparisons#3MrLukeSmith wants to merge 20 commits into
MrLukeSmith wants to merge 20 commits into
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…-db-cpus/--db-memory Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
…_cpu Comparing a mysql result against a postgres result no longer trips the ProfileMismatch guard (that guard only checks topology/resource fields). The Database row is purely informational.
Postgres has no ROUND(double precision, integer) overload, only ROUND(numeric, integer) - discovered via Task 14's manual Postgres smoke run, which failed with 'function round(double precision, integer) does not exist' when fetching top statement digests.
pg_stat_statements' query text can span multiple lines (e.g. Rails' own multi-line schema-introspection queries), which a bare newline-per-row split shreds into bogus extra rows with empty columns - discovered via Task 14's manual Postgres smoke run, whose top_statements output was garbage. psql's --csv mode quotes multi-line fields per RFC4180, so Ruby's CSV library parses them correctly.
Cheap insurance recommended by the final whole-feature review - this bug was only caught by a live Postgres run; without this assertion, reverting the ::numeric cast would stay green in the unit suite.
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Context
Adds Postgres as a second, selectable database engine so we can compare MySQL vs Postgres performance like-for-like with
bin/bench compare.Change summary
--database mysql|postgresflag onbin/bench run(defaultmysql), backed by a newBench::Enginesregistry and aBench::PostgresClientmirroringBench::MysqlClient.docker-compose.ymlgains apostgresservice; only the selected engine's container is started per run.--mysql-cpus/--mysql-memory→--db-cpus/--db-memory,mysql:→db:inprofiles/*.yml,mysql_cpumetric →db_cpu.bin/bench comparenow shows which engine each side used; comparing MySQL vs Postgres under the same profile is not treated as a mismatch.result.jsonfiles predate thedatabase/db_cpufields and thedb_cpusprofile key — comparing an old result against a new one will show blank values for those fields.Technical considerations
ROUND(double precision, integer)overload (needed an explicit::numericcast), andpg_stat_statements' query text can span multiple lines, which broke naive newline-per-row parsing —PostgresClientnow parsespsql --csvoutput via Ruby'sCSVlibrary instead. Both have regression coverage now, but there's no CI job against real Postgres/MySQL containers, so similar issues would again only surface via manualmise run smoke/--database postgresruns.Gemfilenow bundlespgunconditionally; its native extension needslibpqdev headers on the host (documented in the README).