[Improve][Connector-Clickhouse] improve ck batch parallel read by using last batch row sorting value approach, instead of limit offset.#9801
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…ng last batch row sorting value approach, instead of limit offset.
Hisoka-X
reviewed
Sep 1, 2025
| } else { | ||
| return clickhouseSourceSplit.getParts().stream() | ||
| .map(ClickhouseValueReader.this::buildPartQuery) | ||
| .map(this::buildStreamPartQuery) |
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Actually, I just want to separate the methods for building query sql in different modes. The buildBatchSqlQuery and buildBatchPartQuery methods are only used for sql query construction in batch mode. This way, there is no need to make additional logical judgments within the method regarding the generation of sql in the Stream scenario.
Hisoka-X
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Sep 2, 2025
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| Method buildKeysetWhereConditionMethod = | ||
| ClickhouseValueReader.class.getDeclaredMethod( | ||
| "buildKeysetWhereCondition", String.class, List.class); | ||
| buildKeysetWhereConditionMethod.setAccessible(true); |
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Could you reuse
corgy-w
approved these changes
Sep 8, 2025
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Purpose of this pull request
Improve ck batch parallel read by using last batch row sorting value approach, instead of limit offset.
When reading large amounts of data, using the limit offset method will first construct the complete result set and then skip the number of rows specified by the offset. The larger the value of OFFSET is, the higher the cost of the query will be. Therefore, for the optimization of batch reading, the maximum value of the sorting key of the last batch is recorded. This approach utilizes the WHERE condition to "skip" the previous data.
before:
after:
Does this PR introduce any user-facing change?
How was this patch tested?
Check list
New License Guide