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https://issues.apache.org/jira/browse/CALCITE-7906?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18135329#comment-18135329
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Julian Hyde commented on CALCITE-7906:
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This seems related to CALCITE-7153 (simplifying LIKE patterns to make them more
efficient).
> Improve LikePattern to support '_' wildcard and enhance the performance of
> '%' wildcard
> ---------------------------------------------------------------------------------------
>
> Key: CALCITE-7906
> URL: https://issues.apache.org/jira/browse/CALCITE-7906
> Project: Calcite
> Issue Type: Improvement
> Components: core
> Reporter: Ruben Q L
> Assignee: Ruben Q L
> Priority: Major
> Labels: pull-request-available
> Fix For: 1.43.0
>
>
> LikePattern (which handles the patterns passed to JDBC {{DatabaseMetaData}}
> methods such as {{getTables}} and {{getColumns}} and to {{Lookup.getNames}})
> has implements matching via {{likeToRegex}} which turns each % into .* and
> matches with java.util.regex. For example:
> {noformat}
> %%%%%%%%%%x => .*.*.*.*.*.*.*.*.*.*x
> %a%a%a%a%a%a%a%a%a%a%x => .*a.*a.*a.*a.*a.*a.*a.*a.*a.*a.*x
> {noformat}
> A pattern with many wildcards makes the regex engine backtrack heavily when
> the name doesn't match.
> Apart from that, it currently does not support '_' wildcard, as JDBC
> specification requires.
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