Partition by hash formula
Hello,
recently I read
https://blog.dbi-services.com/hash-partitioning-in-postgresql-11/
and reproduced steps from the, which gave exact same count outcome,
which made me think
hashing is a pure function.
Examined the data I saw following distribution:
dept_1: 1,14,39...; dept_2: 3,11,21...; dept_3: 16,18,25...
I also found commit 1aba8e651a introducing the feature, but I'm not too
much into internals.
I wonder, could somebody write that hashing formula in pseudo-code or
point to specific place in the code, please?
Thanks,
Vlad
On Fri, 2020-03-20 at 12:50 +0300, Vlad Bokov wrote:
recently I read
https://blog.dbi-services.com/hash-partitioning-in-postgresql-11/
and reproduced steps from the, which gave exact same count outcome,
which made me think
hashing is a pure function.Examined the data I saw following distribution:
dept_1: 1,14,39...; dept_2: 3,11,21...; dept_3: 16,18,25...I also found commit 1aba8e651a introducing the feature, but I'm not too
much into internals.
I wonder, could somebody write that hashing formula in pseudo-code or
point to specific place in the code, please?
Look for the int4hashfast, texthashfast and similar functions in
src/backend/utils/cache/catcache.c
Yours,
Laurenz Albe
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