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Posted to issues@calcite.apache.org by "Julian Hyde (Jira)" <ji...@apache.org> on 2022/01/25 16:13:00 UTC
[jira] [Commented] (CALCITE-4994) SqlToRelConverter creates FieldMap for every Identifier Instead of Memoizing it
[ https://issues.apache.org/jira/browse/CALCITE-4994?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17481921#comment-17481921 ]
Julian Hyde commented on CALCITE-4994:
--------------------------------------
I haven’t thought about this very much, so I reserve judgment on whether memoization will benefit the average case.
As you claim that there is a particular query that performs poorly without the fix, can you create a test or microbenchmark that demonstrates this.
> SqlToRelConverter creates FieldMap for every Identifier Instead of Memoizing it
> -------------------------------------------------------------------------------
>
> 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
> Time Spent: 10m
> 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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