[jira] [Updated] (CALCITE-963) Hoist literals

["ASF GitHub Bot (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/CALCITE-963?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

ASF GitHub Bot updated CALCITE-963:
-----------------------------------
    Labels: pull-request-available  (was: )

> Hoist literals
> --------------
>
>                 Key: CALCITE-963
>                 URL: https://issues.apache.org/jira/browse/CALCITE-963
>             Project: Calcite
>          Issue Type: Bug
>            Reporter: Julian Hyde
>            Priority: Major
>              Labels: pull-request-available
>
> Convert literals into (internal) bind variables so that statements that differ only in literal values can be executed using the same plan.
> In [mail thread|http://mail-archives.apache.org/mod_mbox/calcite-dev/201511.mbox/%3C56437BF8.70802@gmail.com%3E] Homer wrote:
> {quote}Imagine that it is common to run a large number of very similar machine generated queries that just change the literals in the sql query.
> For example (the real queries would be much more complex):
> {code}Select * from emp where empno = 1;
> Select * from emp where empno = 2;
> etc.{code}
> The plan that is likely being generated for these kind of queries is going to be very much the same each time, so to save some time, I would like to recognize that the literals are all that have changed in a query and use the previously optimized execution plan and just replace the literals.{quote}
> I think this could be done as a transform on the initial RelNode tree. It would find literals (RexLiteral), replace them with bind variables (RexDynamicParam) and write the value into a pool. The next statement would go through the same process and the RelNode tree would be identical, but with possibly different values for the bind variables.
> The bind variables are of course internal; not visible from JDBC. When the statement is executed, the bind variables are implicitly bound.
> Statements would be held in a Guava cache.
> This would be enabled by a config parameter. Unfortunately I don't think we could do this by default -- we'd lose optimization power because we would no longer be able to do constant reduction.



--
This message was sent by Atlassian Jira
(v8.3.4#803005)