Paul Rogers created DRILL-5023:
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Summary: ExternalSortBatch does not spill fully, throws off spill
calculations
Key: DRILL-5023
URL: https://issues.apache.org/jira/browse/DRILL-5023
Project: Apache Drill
Issue Type: Bug
Affects Versions: 1.8.0
Reporter: Paul Rogers
Priority: Minor
The {{ExternalSortBatch}} (ESB) operator sorts records, spilling to disk as
needed to operate within a defined memory budget.
When needed, ESB spills accumulated record batches to disk. However, when doing
so, the ESB carves off the first spillable batch and holds it in memory:
{{code}}
// 1 output container is kept in memory, so we want to hold on to it and
transferClone
// allows keeping ownership
VectorContainer c1 = VectorContainer.getTransferClone(outputContainer,
oContext);
c1.buildSchema(BatchSchema.SelectionVectorMode.NONE);
c1.setRecordCount(count);
...
BatchGroup newGroup = new BatchGroup(c1, fs, outputFile, oContext);
}}
When the spill batch size gets larger (to fix DRILL-5022), the result is that
nothing is spilled as the first spillable batch is simply stored back into
memory on the (supposedly) spilled batches list.
The desired behavior is for all spillable batches to be written to disk. If the
first batch is held back to work around some issue (to keep a schema, say?),
then fine a different solution that allows the actual data to spill.
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