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Make sure we request pages with a known-flushed LSN. (#10413)

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This should fix the largest source of flakyness of
test_nbtree_pagesplit_cycleid.

## Problem

https://github.com/neondatabase/neon/issues/10390

## Summary of changes

By using a guaranteed-flushed LSN, we ensure that PS won't have to wait
forever.

(If it does wait forever, we know the issue can't be with Compute's WAL)
This commit is contained in:
Matthias van de Meent
2025-01-16 09:34:11 +01:00
committed by GitHub
parent 6fe4c6798f
commit 7be971081a
1 changed files with 13 additions and 7 deletions
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20
test_runner/regress/test_nbtree_pagesplit_cycleid.py
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@@ -4,9 +4,19 @@ import time
from fixtures.neon_fixtures import NeonEnv
BTREE_NUM_CYCLEID_PAGES = """
WITH raw_pages AS (
SELECT blkno, get_raw_page_at_lsn('t_uidx', 'main', blkno, NULL, NULL) page
FROM generate_series(1, pg_relation_size('t_uidx'::regclass) / 8192) blkno
WITH lsns AS (
/*
* pg_switch_wal() ensures we have an LSN that
* 1. is after any previous modifications, but also,
* 2. (critically) is flushed, preventing any issues with waiting for
* unflushed WAL in PageServer.
*/
SELECT pg_switch_wal() as lsn
),
raw_pages AS (
SELECT blkno, get_raw_page_at_lsn('t_uidx', 'main', blkno, lsn, lsn) page
FROM generate_series(1, pg_relation_size('t_uidx'::regclass) / 8192) AS blkno,
lsns l(lsn)
),
parsed_pages AS (
/* cycle ID is the last 2 bytes of the btree page */
@@ -36,7 +46,6 @@ def test_nbtree_pagesplit_cycleid(neon_simple_env: NeonEnv):
ses1.execute("CREATE UNIQUE INDEX t_uidx ON t(id);")
ses1.execute("INSERT INTO t (txt) SELECT i::text FROM generate_series(1, 2035) i;")
ses1.execute("SELECT neon_xlogflush();")
ses1.execute(BTREE_NUM_CYCLEID_PAGES)
pages = ses1.fetchall()
assert (
@@ -57,7 +66,6 @@ def test_nbtree_pagesplit_cycleid(neon_simple_env: NeonEnv):
ses1.execute("DELETE FROM t WHERE id <= 610;")
# Flush wal, for checking purposes
ses1.execute("SELECT neon_xlogflush();")
ses1.execute(BTREE_NUM_CYCLEID_PAGES)
pages = ses1.fetchall()
assert len(pages) == 0, f"No back splits with cycle ID expected, got batches of {pages} instead"
@@ -108,8 +116,6 @@ def test_nbtree_pagesplit_cycleid(neon_simple_env: NeonEnv):
# unpin the btree page, allowing s3's vacuum to complete
ses2.execute("FETCH ALL FROM foo;")
ses2.execute("ROLLBACK;")
# flush WAL to make sure PS is up-to-date
ses1.execute("SELECT neon_xlogflush();")
# check that our expectations are correct
ses1.execute(BTREE_NUM_CYCLEID_PAGES)
pages = ses1.fetchall()