zghong opened a new pull request, #66477:
URL: https://github.com/apache/doris/pull/66477
### What problem does this PR solve?
Issue Number: close #66231
Problem Summary:
Hash Bucketing previously supported only the CRC32 hash function to map a
row to its bucket. There was no way for users to choose a different bucketing
scheme, which prevents scenarios (e.g. bucket pruning / colocation with
external systems) that rely on a plain identity mapping of the bucket key, as
shown in #66231.
This PR introduces a table-level `distribution_hash_type` property for Hash
Bucketing tables, supporting two values:
- `crc32` (default, keeps existing behavior), means `crc32(key) %
bucket_num`.
- `identity` (map rows to buckets by the raw key value), means `key %
bucket_num`.
Main changes:
- FE: parse and validate the new `distribution_hash_type` property in
`PropertyAnalyzer`; carry the hash type through `HashDistributionInfo`,
`HashDistributionDesc`, `ColocateGroupSchema`, `DataPartition`,
`DistributionSpecHash` and related create-table / colocate paths; a new
`FeMetaVersion` is added for metadata persistence. `ADD PARTITION` now inherits
the table hash type.
- Nereids: the optimizer is taught to recognize the non-CRC32 (identity)
hash type when reasoning about distribution properties, so shuffle can be
eliminated and bucket pruning (`HashDistributionPruner`, `PruneOlapScanTablet`)
still works correctly for identity buckets.
- BE: `TDistributionHashType` is added to thrift and threaded through the
exchange / local-exchange sink operators and the tablet-sink partitioner so
that the backend uses the same bucketing function as the FE plan, keeping FE/BE
bucketing consistent. An identity partitioner is implemented.
- thrift: add `TDistributionHashType` and propagate the field in
`Descriptors`, `Partitions`, `PlanNodes` and `Types`.
Before this PR: only CRC32 bucketing was available.
After this PR: users can create Hash Bucketing tables with
`"distribution_hash_type" = "identity"`, and FE plan optimization plus BE data
sink produce consistent bucketing results. And more hash functions can be
extended in the future.
### Release note
Support a new table property `distribution_hash_type` for Hash Bucketing
tables. It accepts `crc32` (default) and `identity` now, allowing users to
choose the hash function used to map rows to buckets.
### Check List (For Author)
- Test <!-- At least one of them must be included. -->
- [x] Regression test
- [x] Unit Test
- [ ] Manual test (add detailed scripts or steps below)
- [ ] No need to test or manual test. Explain why:
- [ ] This is a refactor/code format and no logic has been changed.
- [ ] Previous test can cover this change.
- [ ] No code files have been changed.
- [ ] Other reason <!-- Add your reason? -->
- Behavior changed:
- [ ] No.
- [x] Yes. <!-- Explain the behavior change --> A new
`distribution_hash_type` property is added; but default behavior (crc32) is
unchanged.
- Does this need documentation?
- [ ] No.
- [x] Yes. <!-- Add document PR link here. eg:
https://github.com/apache/doris-website/pull/1214 --> Detail docs will be added
after further reviews.
### Check List (For Reviewer who merge this PR)
- [ ] Confirm the release note
- [ ] Confirm test cases
- [ ] Confirm document
- [ ] Add branch pick label <!-- Add branch pick label that this PR should
merge into -->
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