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https://issues.apache.org/jira/browse/HIVE-460?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12714807#action_12714807
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Zheng Shao commented on HIVE-460:
---------------------------------
hive-460-2009-05-29-noaliasallowed.patch:
* HiveStringUtils: I think it's better to use
http://java.sun.com/j2se/1.4.2/docs/api/java/lang/Character.html#isLetterOrDigit(char)
* patch line 103: I think we can revert this change
* patch line 124 & 132: what is the special case for join?
* patch line 334: The replaceAllIllegalCharWithUnderline does not return a
unique string: "a+b" and "a-b" will both become "a_b".
* patch line 362: fields -> fieldNames, also, we need to find a way to get
unique names if there are duplicates.
* patch line 405: we are regenerating the field names here. We should serialize
the field names in the operator desc - this will make sure the way to get
unique names in the compilation time and runtime will be the same.
I think the basic idea is good - we are now using the real expression (or
modified real expression due to illegal chars and duplicates), instead of "0",
"1", "2", as the internal names.
In case of "SELECT a + b as c", I think we should use "c" as internal name. In
case of "SELECT a + b", we just use "a_b" as internal name. If it's "SELECT a +
b, a - b", then we can use "a_b"， "a_b2". What do you think?
BTW, I think "SELECT kv1.key as key_alias, sum(substr(kv1.value,5)) GROUP BY
key_alias LIMIT 5" never worked, so it's not an issue here.
But we definitely need to make sure:
"SELECT field1, field2 FROM (SELECT key + value as field1, key - value as
field2 FROM src) t"
works.
"SELECT * FROM (SELECT key + value, key - value FROM src) t" should also work.
> Improve ColumnPruner to prune more aggressively and keep column information
> for input tables
> --------------------------------------------------------------------------------------------
>
> Key: HIVE-460
> URL: https://issues.apache.org/jira/browse/HIVE-460
> Project: Hadoop Hive
> Issue Type: Improvement
> Components: Query Processor
> Affects Versions: 0.4.0
> Reporter: Zheng Shao
> Assignee: He Yongqiang
> Attachments: hive-460-2009-05-29-noaliasallowed.patch,
> HIVE-460.1.patch
>
>
> This is required for column-based table format.
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