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Update test_runner/performance/test_unlogged.py

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Co-authored-by: Heikki Linnakangas <heikki@neon.tech>
This commit is contained in:
Konstantin Knizhnik
2025-07-22 18:52:17 +03:00
committed by Konstantin Knizhnik
parent 9955d02a01
commit 388be47144
1 changed files with 3 additions and 3 deletions
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test_runner/performance/test_unlogged.py
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@@ -13,9 +13,9 @@ if TYPE_CHECKING:
# This test demonstrates effect of relkind cache. Postgres doesn't store relation persistence in shared buffer tag.
# It means that if page is evicted from shared buffers and relation is not cache in relation cache, then persistence=0 (auto) is used.
# For vanilla Postgres it is not important, because in both cases we need to write changes to the file.
# In Neon for permanent relations neon_write does nothing, while for unlogged relation - should store data in local file.
# Originally Neon uses `mdexists` call to check if local file exists and so determine if it is unlogged relation.
# mdexists is not so cheap: it closes and opens file. Relkind cache allow to eliminate this checks.
# In Neon, neon_write does nothing nothing for a permanent relation, while for an unlogged relation, it writes the page to the local file.
# Originally Neon always called `mdexists` to check if the local file exists and determine if it's an unlogged relation. Now we check the cache first.
# mdexists is not so cheap: it closes and opens the file.
#
# This test tries to emulate situation when most of writes are with persistence=0.
# We create multiple connections to the database and in each fill it's own table. So each backends writes only it's own table and other tables