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https://issues.apache.org/jira/browse/DERBY-6109?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13610181#comment-13610181
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Rick Hillegas commented on DERBY-6109:
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A typical wrapper view looks like this:
create view v as select * from ...
When you use the view in the following query...
select a from v
...the projection which the optimizer pushes down to the table element (base
table or table function) is...
select *
...but you want the optimizer to push down this projection instead...
select a
If you used a synonym instead, I'm supposing that the synonym would be replaced
with the reference to the table element at bind() time, before the optimizer
sees the query. The optimizer would only see "select a" and not "select *", so
"select a" would be pushed down.
Note that I haven't verified that that's what happens with table synonyms
today. In the long run, what we really want to do is fix DERBY-6036.
> Allow CREATE SYNONYM for table function invocations.
> ----------------------------------------------------
>
> Key: DERBY-6109
> URL: https://issues.apache.org/jira/browse/DERBY-6109
> Project: Derby
> Issue Type: Improvement
> Components: SQL
> Affects Versions: 10.10.1.1
> Reporter: Rick Hillegas
>
> SYNONYMs are a non-standard extension supported by many databases. See
> DERBY-335. Right now SYNONYMs are only allowed for tables and views. It would
> be useful (and should be easy) to extend this feature to support SYNONYMs for
> table function invocations. E.g.:
> CREATE SYNONYM LT0 for TABLE( LT0() )
> CREATE SYNONYM LT0_P for TABLE( LT0('with_provenance') )
> See the discussion of this topic on this email thread:
> http://apache-database.10148.n7.nabble.com/Limitations-of-Table-Functions-vs-old-VTIs-td127988.html
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