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https://issues.apache.org/jira/browse/HIVE-4070?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13667121#comment-13667121
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Edward Capriolo commented on HIVE-4070:
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The risk, as I see it, is that there are already a large number of people
depending on the current behaviour. If we change the default that would change
the results current users are getting. Better that the new users learn how hive
works, since they are learning anyway, then break assumptions of current users.
Most users do not want to have to heavily test before upgrade, they want
consistent behaviour between versions.
You suggestion to have a global or session level property is a good one. There
are some cases where I have thought about doing this. In general, it is not
ideal because no other component in hive works this way. Thus having a one-off
configuration for handling how like statements work is odd. Also the query is
no longer self documenting. Based on how some parameter outside the query is
set, the system functions differently. Imagine if we had 10 such parameters
could the same query produce 100 different results based on permutations of
properties?
For the most part, we model functionality in hive based on what mysql does. You
will find a lot of compatibility in how UDFs work and other language features.
There are many ways this can be dealt with, hive has 'like' and 'rlike'. If
there is an sql standard on how like must work that might be ammo for the
argument of changing the default, but basing a change solely on how mysql does
something just for new users is not attractive. MySQL has made its own bad
choices over the years (non standard things like enum) (non standard date/time
types) (non standard ways to specify indexes).
I am guessing that hive's like is the way it is because hive initially only
supported java's UTf8 strings and that comparison is by default case sensitive.
> Like operator in Hive is case sensitive while in MySQL (and most likely other
> DBs) it's case insensitive
> --------------------------------------------------------------------------------------------------------
>
> Key: HIVE-4070
> URL: https://issues.apache.org/jira/browse/HIVE-4070
> Project: Hive
> Issue Type: Bug
> Components: UDF
> Affects Versions: 0.10.0
> Reporter: Mark Grover
> Assignee: Mark Grover
> Priority: Trivial
>
> Hive's like operator seems to be case sensitive.
> See
> https://github.com/apache/hive/blob/trunk/ql/src/java/org/apache/hadoop/hive/ql/udf/UDFLike.java#L164
> However, MySQL's like operator is case insensitive. I don't have other DB's
> (like PostgreSQL) installed and handy but I am guessing their LIKE is case
> insensitive as well.
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