wjhypo opened a new pull request #9810:
URL: https://github.com/apache/druid/pull/9810
Fixes #9809.
### Description
Currently segment pruning uses the time interval. For further filtering on
secondary partitions, only single dimension ShardSpec is supported (done in
#2982). For hash based partitioning (`HashBasedNumberedShardSpec`), we can also
apply pruning by rehash the `partitionDimensions` in the query filter to locate
segments.
This PR addresses this by rehashing the `partitionDimensions` values in
`HashBasedNumberedShardSpec` from the query filter using the same hashing
mechanism used during ingestion, and use the hashed value mod `partitions` to
determine if it equals `partitionNum` of a segment. We only attempt pruning if
1) all `partitionDimensions` present in the query filter and 2) the values of
`partitionDimensions` are discrete values not range values because we can't
hash range values and 3) during ingestion time, `partitionDimensions` are
explicitly set because otherwise the hash during ingestion is based on all
dimensions plus the truncated input timestamp according to QueryGranularity
instead of just `partitionDimensions` and we don't record timestamp in shard
spec. Then we enumerate all combinations of the values of the dimensions in
`partitionDimensions` drawn from the filter and check if the hashed value mod
`partitions` matches the `partitionNum` of a segment. E.g., if the query
contains filter "dim1 = v1 and dim2 in (v2, v3, v4)", then the hash values we
will check are: hash(v1, v2), hash(v1, v3), hash(v1, v4).
This PR has:
- [x] been self-reviewed.
- [ ] using the [concurrency
checklist](https://github.com/apache/druid/blob/master/dev/code-review/concurrency.md)
(Remove this item if the PR doesn't have any relation to concurrency.)
- [x] added documentation for new or modified features or behaviors.
- [x] added Javadocs for most classes and all non-trivial methods. Linked
related entities via Javadoc links.
- [ ] added or updated version, license, or notice information in
[licenses.yaml](https://github.com/apache/druid/blob/master/licenses.yaml)
- [x] added comments explaining the "why" and the intent of the code
wherever would not be obvious for an unfamiliar reader.
- [x] added unit tests or modified existing tests to cover new code paths.
- [ ] added integration tests.
- [x] been tested in a test Druid cluster.
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