_ensureCollection() runs once per document on the embed path, but only
createCollection sat behind the collectionExists guard — the
getCollections probe and the three createPayloadIndex calls fired
unconditionally every time. On large ZIM ingestions those redundant
requests consumed roughly 45% of per-document Qdrant time, making jobs
look stalled while they were slowly progressing.
Memoize ensured collections in a per-instance Set, recorded only after
every step succeeds so partial failures retry. The cache is cleared
when the Qdrant health check resets the client (server may have been
recreated), and the entry is dropped before resetAndRebuild()
recreates the collection it just deleted.
Memoizing instead of moving the index calls inside the guard keeps
missing indexes healing on collections that predate the current
payload schema.
Closes#1129
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>
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