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https://issues.apache.org/jira/browse/CALCITE-7618?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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ASF GitHub Bot updated CALCITE-7618:
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Labels: pull-request-available (was: )
> Add filter pushdown support to the file adapter's CSV table implementation
> --------------------------------------------------------------------------
>
> Key: CALCITE-7618
> URL: https://issues.apache.org/jira/browse/CALCITE-7618
> Project: Calcite
> Issue Type: Improvement
> Components: file-adapter
> Reporter: Diveyam Mishra
> Assignee: Diveyam Mishra
> Priority: Minor
> Labels: pull-request-available
>
> The file adapter's CSV implementation currently supports projection pushdown
> but does not appear to support filter pushdown.
> For example:
> {code}
> SELECT name, empno
> FROM EMPS
> WHERE deptno = 20
> {code}
> The resulting plan is:
> {code}
> PLAN=EnumerableCalc(expr#0..2=[\{inputs}], expr#3=[20], expr#4=[=($t2, $t3)],
> NAME=[$t1], EMPNO=[$t0], $condition=[$t4])
> CsvTableScan(table=[[SALES, EMPS]], fields=[[0, 1, 2]])
> {code}
> Desired Plan could be something like:
> {code}
> CsvTableScan(..., filters=[deptno=20])
> {code}
> The filter condition is evaluated in the upper \{{EnumerableCalc}} node
> rather than during the CSV scan itself. As a result, all rows are read from
> the underlying CSV file and filtering occurs afterward.
> The file adapter already contains infrastructure related to filtering:
> * {\{CsvEnumerator}} contains \{{filterValues}}-based row filtering logic.
> * {\{CsvTable}} was originally derived from the demo CSV adapter's
> filterable implementation.
> * The file adapter defines table flavors including \{{FILTERABLE}}.
> However, the file adapter currently exposes \{{CsvTranslatableTable}}, and
> there does not appear to be a mechanism that translates pushdown-compatible
> filter predicates into the filtering capabilities already present in
> \{{CsvEnumerator}}.
> Evidence:
> * Physical plan for the query above contains \{{EnumerableCalc}} over
> \{{CsvTableScan}}.
> * Planner logs show projection pushdown via \{{CsvProjectTableScanRule}}.
> * No file-adapter-specific filter pushdown rule appears to fire.
> * Filter evaluation remains outside the scan.
> This results in unnecessary parsing and processing of rows that could
> potentially be eliminated during scanning.
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