peter
608fde2d55
A concurrent build that failed part-way leaves an INVALID index under its name; IF NOT EXISTS kept it on the re-run, and 0095 then dropped the old channel_id index, leaving none usable. The leftover is now dropped and built again, and the old index goes only once the new one is valid.
54 lines
2.2 KiB
Python
54 lines
2.2 KiB
Python
"""A concurrent index build that failed part-way, then re-run (E31 S5 review), DB-lane.
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CREATE INDEX CONCURRENTLY that fails leaves an INVALID index under its name, and alembic_version is not
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stamped, so the next start runs the migration again. `IF NOT EXISTS` matched the name and kept the
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leftover, which the planner never uses; 0095 then dropped the old channel_id index, leaving `videos`
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with no usable one. A re-run now rebuilds the leftover and drops the old index only once the new one is
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valid.
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"""
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from alembic import command
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from alembic.config import Config
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from sqlalchemy import text
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from app.db import engine
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def _index(name: str) -> tuple[bool, str] | None:
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with engine.connect() as conn:
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row = conn.execute(
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text(
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"SELECT i.indisvalid, pg_get_indexdef(i.indexrelid) FROM pg_index i "
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"JOIN pg_class c ON c.oid = i.indexrelid WHERE c.relname = :name"
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),
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{"name": name},
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).first()
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return None if row is None else (bool(row[0]), row[1])
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def _leave_invalid(name: str) -> None:
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"""What a build that failed part-way leaves behind: the name taken, the index INVALID."""
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with engine.connect().execution_options(isolation_level="AUTOCOMMIT") as conn:
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conn.execute(text(f"CREATE INDEX {name} ON videos (id)"))
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conn.execute(
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text(f"UPDATE pg_index SET indisvalid = false WHERE indexrelid = '{name}'::regclass")
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)
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def test_a_rerun_rebuilds_an_invalid_leftover_before_dropping_the_old_index(db):
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db.rollback() # CONCURRENTLY waits for every open transaction, this session's too
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cfg = Config("alembic.ini")
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command.downgrade(cfg, "0094_plex_genres_hu_everywhere")
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try:
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_leave_invalid("ix_videos_channel_pub_cover")
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_leave_invalid("ix_videos_views_desc")
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finally:
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command.upgrade(cfg, "head")
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cover = _index("ix_videos_channel_pub_cover")
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assert cover is not None and cover[0], cover
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assert "INCLUDE (duration_seconds" in cover[1]
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assert _index("ix_videos_channel_pub_desc") is None
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views = _index("ix_videos_views_desc")
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assert views is not None and views[0] and "view_count DESC NULLS LAST" in views[1], views
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