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https://issues.apache.org/jira/browse/CALCITE-4994?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Liya Fan closed CALCITE-4994.
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Resolved in release 1.30.0 (2022-03-20)
> SQL-to-RelNode conversion is slow if table contains hundreds of fields
> ----------------------------------------------------------------------
>
> Key: CALCITE-4994
> URL: https://issues.apache.org/jira/browse/CALCITE-4994
> Project: Calcite
> Issue Type: Improvement
> Components: core
> Reporter: Jay Narale
> Priority: Major
> Labels: pull-request-available
> Fix For: 1.30.0
>
> Time Spent: 40m
> Remaining Estimate: 0h
>
> When converting from Sql To Rel, In SqlToRelConverter for every single
> instance of an identifier we create a new map in
> *_org.apache.calcite.sql2rel.SqlToRelConverter.Blackboard#lookupExp_*
>
> {code:java}
> final Map<String, Integer> fieldOffsets = new HashMap<>();
> for (RelDataTypeField f : resolve.rowType().getFieldList()) {
> if (!fieldOffsets.containsKey(f.getName())) {
> fieldOffsets.put(f.getName(), f.getIndex());
> }
> }
> final Map<String, Integer> map = ImmutableMap.copyOf(fieldOffsets);{code}
>
> So for a Sql Query
> {code:java}
> SELECT name, nation FROM customer{code}
> We would do the above operation twice.
> Memoization of this information will improve performance.
> In my database, I had observed that for a large table involving 1200 columns
> and a huge select having multiple expressions and operators, this part was a
> bottleneck.
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