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https://issues.apache.org/jira/browse/HIVE-3745?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13766654#comment-13766654
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Eugene Koifman commented on HIVE-3745:
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Making this configurable may be difficult: suppose you have a join with ON
clause comparing 2 strings and the join is a hash join. This setting would
affect how hash table is built/probed (depending on how one chooses to
implement this) and any other operator that relies on hashing. Predicate
pushdown and index building/usage could be affected.
I've see DBs that ignore trailing white space and some that do not. I've also
seen some that are case sensitive and some that are not. (Unfortunately I
don't have a complete list, SQL server is insensitive, for example)
> Hive does improper "=" based string comparisons for strings with trailing
> whitespaces
> -------------------------------------------------------------------------------------
>
> Key: HIVE-3745
> URL: https://issues.apache.org/jira/browse/HIVE-3745
> Project: Hive
> Issue Type: Bug
> Components: SQL
> Affects Versions: 0.9.0
> Reporter: Harsh J
> Assignee: Kevin Wilfong
>
> Compared to other systems such as DB2, MySQL, etc., which disregard trailing
> whitespaces in a string used when comparing two strings with the "{{=}}"
> relational operator, Hive does not do this.
> For example, note the following line from the MySQL manual:
> http://dev.mysql.com/doc/refman/5.1/en/char.html
> {quote}
> All MySQL collations are of type PADSPACE. This means that all CHAR and
> VARCHAR values in MySQL are compared without regard to any trailing spaces.
> {quote}
> Hive still is whitespace sensitive and regards trailing spaces of a string as
> worthy elements when comparing. Ideally {{LIKE}} should consider this
> strongly, but {{=}} should not.
> Is there a specific reason behind this difference of implementation in Hive's
> SQL?
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