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## Problem LFC is not enabled by default in tests, but it is enabled in production. This increases the risk of errors in the production environment, which were not found during the routine workflow. However, enabling LFC for all the tests may overload the disk on our servers and increase the number of failures. So, we try enabling LFC in one case to evaluate the possible risk. ## Summary of changes A new environment variable, USE_LFC is introduced. If it is set to true, LFC is enabled by default in all the tests. In our workflow, we enable LFC for PG17, release, x86-64, and disabled for all other combinations. --------- Co-authored-by: Alexey Masterov <alexeymasterov@neon.tech> Co-authored-by: a-masterov <72613290+a-masterov@users.noreply.github.com>
86 lines
3.1 KiB
Python
86 lines
3.1 KiB
Python
from __future__ import annotations
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from pathlib import Path
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import pytest
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from fixtures.log_helper import log
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from fixtures.neon_fixtures import NeonEnv
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from fixtures.utils import USE_LFC
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@pytest.mark.skipif(not USE_LFC, reason="LFC is disabled, skipping")
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def test_explain_with_lfc_stats(neon_simple_env: NeonEnv):
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env = neon_simple_env
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cache_dir = Path(env.repo_dir) / "file_cache"
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cache_dir.mkdir(exist_ok=True)
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log.info("Creating endpoint with 1MB shared_buffers and 64 MB LFC")
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endpoint = env.endpoints.create_start(
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"main",
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config_lines=[
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"neon.max_file_cache_size='128MB'",
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"neon.file_cache_size_limit='64MB'",
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],
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)
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cur = endpoint.connect().cursor()
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log.info(f"preparing some data in {endpoint.connstr()}")
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ddl = """
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CREATE TABLE pgbench_accounts (
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aid bigint NOT NULL,
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bid integer,
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abalance integer,
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filler character(84),
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-- more web-app like columns
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text_column_plain TEXT DEFAULT repeat('NeonIsCool', 5),
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jsonb_column_extended JSONB DEFAULT ('{ "tell everyone": [' || repeat('{"Neon": "IsCool"},',9) || ' {"Neon": "IsCool"}]}')::jsonb
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)
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WITH (fillfactor='100');
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"""
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cur.execute(ddl)
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cur.execute(
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"insert into pgbench_accounts(aid,bid,abalance,filler) select aid, (aid - 1) / 100000 + 1, 0, '' from generate_series(1, 100000) as aid;"
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)
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log.info(f"warming up caches with sequential scan in {endpoint.connstr()}")
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cur.execute("SELECT * FROM pgbench_accounts WHERE abalance > 0")
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log.info("running explain analyze without LFC values to verify they do not show up in the plan")
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cur.execute("EXPLAIN (ANALYZE, BUFFERS) SELECT * FROM pgbench_accounts WHERE abalance > 0")
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rows = cur.fetchall()
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plan = "\n".join(r[0] for r in rows)
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log.debug(plan)
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assert "Seq Scan on pgbench_accounts" in plan
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assert "Buffers: shared hit" in plan
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assert "File cache: hits=" not in plan
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log.info("running explain analyze WITH LFC values to verify they do now show up")
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cur.execute(
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"EXPLAIN (ANALYZE, BUFFERS,FILECACHE) SELECT * FROM pgbench_accounts WHERE abalance > 0"
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)
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rows = cur.fetchall()
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plan = "\n".join(r[0] for r in rows)
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log.debug(plan)
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assert "Seq Scan on pgbench_accounts" in plan
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assert "Buffers: shared hit" in plan
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assert "File cache: hits=" in plan
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log.info("running explain analyze WITH LFC values to verify json output")
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cur.execute(
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"EXPLAIN (ANALYZE, BUFFERS,FILECACHE, FORMAT JSON) SELECT * FROM pgbench_accounts WHERE abalance > 0"
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)
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jsonplan = cur.fetchall()[0][0]
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log.debug(jsonplan)
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# Directly access the 'Plan' part of the first element of the JSON array
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plan_details = jsonplan[0]["Plan"]
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# Extract "File Cache Hits" and "File Cache Misses"
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file_cache_hits = plan_details.get("File Cache Hits")
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file_cache_misses = plan_details.get("File Cache Misses")
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# Now you can assert the values
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assert file_cache_hits >= 5000, f"Expected File Cache Hits to be > 5000, got {file_cache_hits}"
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assert file_cache_misses == 0, f"Expected File Cache Misses to be 0, got {file_cache_misses}"
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