Update client varcache with canonical values from server#879
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JelteF merged 1 commit intoDec 30, 2023
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This makes caching variable caching with PgBouncer more efficient, because now the client is setting the same values that the server reports. See these PgBouncer issues/PRs for details: pgbouncer/pgbouncer#776 pgbouncer/pgbouncer#879
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davecramer
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This makes caching variable caching with PgBouncer more efficient, because now the client is setting the same values that the server reports. See these PgBouncer issues/PRs for details: pgbouncer/pgbouncer#776 pgbouncer/pgbouncer#879
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I did some basic benchmarks against PG15 using: And the TPS is as follows on my machine:
If I introduce 10ms of artificial latency between PgBouncer and Postgres then it goes from:
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Since PG14, Postgres doesn't send ParameterStatus packets anymore when a setting has not actually changed. This could cause the client varcache and server varcache to become out of sync. Which then in turn resulted in unnecessary `SET` commands to be sent to the server. Fixes pgbouncer#776
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I tested this fix with PG 16.0. It looks good from functional perspective. The downside is the overhead of checking the startup parameters against the canonical ones for every new client connection even if such clients might be in minority. But I am not sure if this feature should be made opt-in. Since the size of varcache we need to iterate for every new connection is so small, the perf hit should be negligible. So, IMO, it does not worth it to introduce a yet another config param. |
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Since PG14, Postgres doesn't send ParameterStatus packets anymore when a
setting has not actually changed. This could cause the client varcache
and server varcache to become out of sync. Which then in turn resulted
in unnecessary
SETcommands to be sent to the server.Fixes #776