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fix(retrieval): support PostgreSQL 17+ checkpoint stats in capacity probe #496

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fix(retrieval): support PostgreSQL 17+ checkpoint stats in capacity probe #496

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23 changes: 21 additions & 2 deletions scripts/publication_benchmark/capacity_execution.py
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Original file line number Diff line number Diff line change
Expand Up @@ -47,9 +47,28 @@ class CapacityBatch:
container_name: str | None = None


def _pg_checkpoints_fragment(engine) -> str:
"""Return the checkpoint-count subselect for this PostgreSQL version.

PostgreSQL 17 moved checkpoint stats out of ``pg_stat_bgwriter`` into
``pg_stat_checkpointer`` (columns renamed to ``num_timed``/
``num_requested``), and pre-17 PostgreSQL keeps them in
``pg_stat_bgwriter`` (``checkpoints_timed``/``checkpoints_req``).
Detect the server version so the capacity probe works on both.
"""
with engine.connect() as connection:
version_number = int(
connection.execute(text("SHOW server_version_num")).scalar_one()
)
if version_number >= 170000:
return "(SELECT num_timed + num_requested FROM pg_stat_checkpointer)"
return "(SELECT checkpoints_timed + checkpoints_req FROM pg_stat_bgwriter)"


def _database_resources(database_url: str, spec: RetrievalProbeSpec) -> dict[str, int]:
engine = create_engine(database_url_for_owner(database_url, owner="sync"))
try:
checkpoints_fragment = _pg_checkpoints_fragment(engine)
with engine.connect() as connection:
row = (
connection.execute(
Expand All @@ -58,8 +77,8 @@ def _database_resources(database_url: str, spec: RetrievalProbeSpec) -> dict[str
"(SELECT temp_bytes FROM pg_stat_database WHERE datname = current_database()) "
"AS temp_bytes, (SELECT deadlocks FROM pg_stat_database "
"WHERE datname = current_database()) AS deadlocks, "
"(SELECT checkpoints_timed + checkpoints_req FROM pg_stat_bgwriter) "
"AS checkpoints, pg_database_size(current_database()) AS database_bytes, "
+ checkpoints_fragment
+ " AS checkpoints, pg_database_size(current_database()) AS database_bytes, "
"(SELECT coalesce(sum(pg_relation_size(c.oid)), 0) FROM pg_class c "
"WHERE c.relkind IN ('r', 'm') AND c.relnamespace IN "
"(SELECT oid FROM pg_namespace WHERE nspname = 'public')) AS table_bytes, "
Expand Down