Merge pull request #2638 from arc53/better-index-pg

Create 0027_user_logs_agent_lookup_idx.py

application/alembic/versions/0028_user_logs_agent_lookup_idx.py

@@ -0,0 +1,114 @@
+"""0028 index the per-agent log lookups so /api/get_user_logs stops timing out.
+
+The per-agent Logs timeline filters ``user_logs`` on two JSONB keys
+(``data->>'api_key'`` / ``data->>'agent_id'``) and ``stack_logs`` on
+``(agent_id OR api_key)``. None of those had a usable index, so both branches
+seq-scanned.
+
+``user_logs`` is the expensive one, and not for the obvious reason: its heap is
+only ~107 MB but ``data`` is a ~1.16 GB TOAST, and filtering on a JSONB key
+forces a detoast of *every* row. Measured on prod (99,535 rows): **618,809
+buffer accesses to return 6,012 rows — 4.5 s warm, >90 s cold**, against a 30 s
+``STATEMENT_TIMEOUT_MS``. That warm/cold spread is why the endpoint failed
+intermittently rather than always. (``stack_logs`` seq-scans too but stays
+~38 ms: its filter columns live in the heap, so its own 1.9 GB TOAST is never
+touched.)
+
+The two expression indexes turn that detoast scan into a direct lookup. They
+also give the planner statistics on the expressions, which it badly lacked —
+it estimated 974 rows where the truth was 6,012.
+
+``stack_logs (api_key)`` matters for a subtler reason: 0026 added
+``ix_stack_logs_agent_id`` and it works well in isolation (1,759 buffers /
+11.6 ms), but the query ORs it against the unindexed ``api_key`` and Postgres
+cannot BitmapOr when only one side is indexed — so the new index was being
+bypassed entirely. Indexing the second arm is what actually activates it.
+
+Indexes are built ``CONCURRENTLY`` in autocommit blocks (following 0018): a
+plain CREATE INDEX would take an ACCESS EXCLUSIVE lock on a 1.3 GB table on a
+live database. The ``user_logs`` builds each detoast the full ~1.16 GB once, so
+they are not instant; CONCURRENTLY keeps them non-blocking. Because a cancelled
+concurrent build leaves an INVALID index behind that ``IF NOT EXISTS`` would
+then skip forever, each build first clears such a leftover — see
+``_rebuild_if_invalid``. Idempotent both ways.
+
+Revision ID: 0028_user_logs_agent_lookup_idx
+Revises: 0027_schedule_run_error_types
+"""
+
+from typing import Sequence, Union
+
+from alembic import op
+
+
+revision: str = "0028_user_logs_agent_lookup_idx"
+down_revision: Union[str, None] = "0027_schedule_run_error_types"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+# Partial: only rows that actually carry the key are ever looked up by it, and
+# most user_logs rows (owner chats) carry neither, so this keeps the indexes
+# small without changing which rows they can answer for.
+_INDEXES = (
+    (
+        "user_logs_data_api_key_idx",
+        "user_logs ((data->>'api_key'))",
+        "(data->>'api_key') IS NOT NULL",
+    ),
+    (
+        "user_logs_data_agent_id_idx",
+        "user_logs ((data->>'agent_id'))",
+        "(data->>'agent_id') IS NOT NULL",
+    ),
+    (
+        "stack_logs_api_key_idx",
+        "stack_logs (api_key)",
+        "api_key IS NOT NULL",
+    ),
+)
+
+
+def _rebuild_if_invalid(name: str) -> None:
+    """Drop ``name`` only when a previous concurrent build left it INVALID.
+
+    A failed/cancelled ``CREATE INDEX CONCURRENTLY`` does not roll back — it
+    leaves an index in the catalog with ``indisvalid = false`` that still owns
+    the name. ``IF NOT EXISTS`` then skips it forever, so the migration reports
+    success while the planner refuses to use the index: a silent no-op. Clearing
+    it first makes the rebuild actually happen.
+
+    The check is deliberately conditional rather than an unconditional drop
+    (0018's approach): the ``user_logs`` builds detoast ~1.16 GB each, so
+    re-running this migration against a healthy database should not pay that
+    cost again. ``to_regclass`` returns NULL for a name that doesn't exist, so
+    the first run selects no row and skips the drop.
+    """
+    invalid = (
+        op.get_bind()
+        .exec_driver_sql(
+            "SELECT NOT indisvalid FROM pg_index "
+            f"WHERE indexrelid = to_regclass('{name}')"
+        )
+        .scalar()
+    )
+    if invalid:
+        op.execute(f"DROP INDEX CONCURRENTLY IF EXISTS {name};")
+
+
+def upgrade() -> None:
+    # CONCURRENTLY can't run inside a transaction; the autocommit block lets
+    # each build run without locking out writers on a multi-GB live table.
+    for name, target, predicate in _INDEXES:
+        with op.get_context().autocommit_block():
+            _rebuild_if_invalid(name)
+            op.execute(
+                f"CREATE INDEX CONCURRENTLY IF NOT EXISTS {name} "
+                f"ON {target} WHERE {predicate};"
+            )
+
+
+def downgrade() -> None:
+    for name, _target, _predicate in reversed(_INDEXES):
+        with op.get_context().autocommit_block():
+            op.execute(f"DROP INDEX CONCURRENTLY IF EXISTS {name};")