[jira] [Resolved] (CALCITE-4994) SQL-to-RelNode conversion is slow if table contains hundreds of fields

["Julian Hyde (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/CALCITE-4994?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Julian Hyde resolved CALCITE-4994.
----------------------------------
    Fix Version/s: 1.30.0
       Resolution: Fixed

Fixed in [e6f7cac6|https://github.com/apache/calcite/commit/e6f7cac6a2fc4cd4ddf9dc6f29723947cbf99afe]; thanks for the PR, [~jaynarale]!

> 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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