Quantify small changes to predicate evaluation

Hello everybody,

I am currently trying to squeeze some performance out of the current
predicate evaluation implementation. In fact I was able to get some positive
results.
I have some more points on my developement plan, but I am facing the problem
that theses changes will only help very little when talking about runtimes.

Therefore I am not able to quantify these changes at the moment as my
overall query runtimes do not seem to be stable across instance restarts.

Consider the following example:
Start postgres, run to warm up buffers
measure query wall clock time: 24.141s
Stop Postgres:

Start postgres, run to warm up buffers
measure query wall clock time: 25.845
Stop Postgres

I expect my current changes to be resposible for about 0.2-0.3s for this
query but because of the huge time differences I am not able to quantify my
changes.

Maybe somebody can tell me about a better approach to quantify my changes or
give me some input on how to get more stable postgres time measurements.

Thank you very much.

Kind regards

Dennis

If needed please find some configuration parameters below
max_connections = 2
superuser_reserved_connections = 1
ssl = off
shared_buffers = 20GB
max_prepared_transactions = 0
work_mem = 500MB
fsync = off
archive_mode = off
hot_standby = off
effective_cache_size = 20GB
logging_collector = off
debug_print_parse = off
debug_print_rewritten = off
debug_print_plan = off
debug_pretty_print = off
log_checkpoints = off
log_connections = off
log_disconnections = off
log_duration = off
log_hostname = off
track_activities = off
track_counts = off
track_io_timing = off
track_functions = none
log_parser_stats = off
log_planner_stats = off
log_executor_stats = off
log_statement_stats = off
autovacuum = off

--
View this message in context: http://postgresql.1045698.n5.nabble.com/Quantify-small-changes-to-predicate-evaluation-tp5807190.html
Sent from the PostgreSQL - hackers mailing list archive at Nabble.com.