CNDB-12342 Fix query view builder inifinite loop #1516
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pkolaczk
commented
Jan 17, 2025
pkolaczk
commented
- Revert "CNDB-12342: Avoid unnecessary looping in QueryView#build (CNDB-12342: Avoid unnecessary looping in QueryView#build #1491)" (Revert "CNDB-12342: Avoid unnecessary looping in QueryView#build (#1491)" #1510)
- CNDB-12342: Avoid unnecessary looping in QueryView#build
Instead of matching sstables and memtables to indexes we know, go in the opposite direction: find a corresponding index for each sstable and memtable. That limits the necessity of retrying. It also has an additional benefit of detecting reliably the situation when the indexes are suddenly dropped during the query or when the indexes are permanently missing for any other reason - we can signal those situations immediately with an exception instead of looping until the query timeout. Retrying is only needed whenever an index view update happens (e.g. due to a flush or compaction) and the index view is temporarily out of sync from the C* View. We now detect this situation more accurately than before - the SAI View class now keeps track not only of the indexes, but also of all the sstables regardless of their index status. This way we can quickly check if current index view is up to date by consulting its sstable list. See View#containsSSTableIndex and View#isAwareOfSSTable. For memtables we don't have a similar mechanism of detecting in-flight memtable index set update yet, but fortunately memtables are created empty, so when a new memtable appears, and we miss it, we don't introduce a correctness problem. We just need to be a bit more careful on memtable / memtable index removal - we need to make sure we capture the sstable and sstable indexes flushed from the memtable, so if we don't find the memtable index, we retry once.
pkolaczk
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