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## Summary
Replacing a replaceable or addressable event soft-deletes the previous
head, but its `event_mentions` rows stayed behind. Only the hard-delete
kinds (read-state and mesh status) removed theirs, in a separate
statement. No mention-index read (`#p` filters and feeds) returns a
soft-deleted event, so those rows are pure cost: every `#p` read walks
them and throws them away.
A kind:39002 roster republish leaves one dead row per channel member, so
a large channel piles them up with every join. Relay-emitted replaceable
lists with p-tags do the same.
The statement that retires the old head now deletes that head's mention
rows as well, through a data-modifying CTE over `RETURNING id`, on all
three supersede paths:
- the relay's kind:39002 roster writer
(`LockedMemberSnapshot::replace_member_event`)
- `replace_addressable_event` (kind 0/3/10000–19999, including the
relay-signed kind:13535 list)
- the NIP-33 parameterized path
Because the CTE covers every row the retire statement touches, a
coordinate that somehow had more than one live row also gets cleaned up.
The shared `superseded_with_mentions_sql!` macro sits at the crate root
so all three mention-indexing replacement paths use the same statement.
The kind:13534 membership-list and push-lease writers also retire heads,
with a bare `UPDATE`, but neither indexes p-tags, so they leave no
mention rows.
## What got simpler
The hard-delete special case (`if hard_delete_superseded { DELETE FROM
event_mentions … }`) is gone. Both retire statements go through one
macro, so a head and its mention rows leave together on all three paths.
## Not in this PR
- Mention rows already left behind by earlier supersedes.
`docs/database.md` rules out data backfills in migrations, so these get
cleaned up out of band, in batches.
- Other soft-delete paths (NIP-09 deletion, moderation, channel deletion
retiring its 39000–39002 events) also keep mention rows. They are
low-volume, and are noted here as identified debt.
## Tests
`superseded_heads_drop_their_mention_rows` (pg) has one table row per
supersede path: the member-snapshot roster writer (lock, replace,
release), the addressable path, the NIP-33 path, and the two NIP-33
kinds that are hard-deleted (NIP-RS read state and mesh status). In each
case the old head keeps zero mention rows and the new head is indexed.
Soft-delete rows check that the old head stays soft-deleted, and
hard-delete rows check that it is gone. Reverting the macro, any single
call site, or the hard-delete statement alone fails this test.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
---------
Signed-off-by: Luke Tornquist <tornquist@squareup.com>
Co-authored-by: Elrond <28d6302a099e5225b02c4155ac4236e4912603df2ab08dbfc2f4fef08ce598c8@buzz.block.builderlab.xyz>
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>