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https://issues.apache.org/jira/browse/HIVE-12274?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Naveen Gangam updated HIVE-12274:
---------------------------------
Status: Open (was: Patch Available)
The precommit build failed with some ptest error. It did not run the tests at
all. Will re-submit the patch to kick off the build
> Increase width of columns used for general configuration in the metastore.
> --------------------------------------------------------------------------
>
> Key: HIVE-12274
> URL: https://issues.apache.org/jira/browse/HIVE-12274
> Project: Hive
> Issue Type: Improvement
> Components: Metastore
> Affects Versions: 2.0.0
> Reporter: Elliot West
> Assignee: Naveen Gangam
> Labels: metastore
> Attachments: HIVE-12274.example.ddl.hql, HIVE-12274.patch,
> HIVE-12274.patch
>
>
> h2. Overview
> This issue is very similar in principle to HIVE-1364. We are hitting a limit
> when processing JSON data that has a large nested schema. The struct
> definition is truncated when inserted into the metastore database column
> {{COLUMNS_V2.YPE_NAME}} as it is greater than 4000 characters in length.
> Given that the purpose of these columns is to hold very loosely defined
> configuration values it seems rather limiting to impose such a relatively low
> length bound. One can imagine that valid use cases will arise where
> reasonable parameter/property values exceed the current limit.
> h2. Context
> These limitations were in by the [patch
> attributed|https://github.com/apache/hive/commit/c21a526b0a752df2a51d20a2729cc8493c228799]
> to HIVE-1364 which mentions the _"max length on Oracle 9i/10g/11g"_ as the
> reason. However, nowadays the limit can be increased because:
> * Oracle DB's {{varchar2}} supports 32767 bytes now, by setting the
> configuration parameter {{MAX_STRING_SIZE}} to {{EXTENDED}}.
> ([source|http://docs.oracle.com/database/121/SQLRF/sql_elements001.htm#SQLRF55623])
> * Postgres supports a max of 1GB for {{character}} datatype.
> ([source|http://www.postgresql.org/docs/8.3/static/datatype-character.html])
> * MySQL can support upto 65535 bytes for the entire row. So long as the
> {{PARAM_KEY}} value + {{PARAM_VALUE}} is less than 65535, we should be good.
> ([source|http://dev.mysql.com/doc/refman/5.0/en/char.html])
> * SQL Server's {{varchar}} max length is 8000 and can go beyond using
> "varchar(max)" with the same limitation as MySQL being 65535 bytes for the
> entire row. ([source|http://dev.mysql.com/doc/refman/5.0/en/char.html])
> * Derby's {{varchar}} can be upto 32672 bytes.
> ([source|https://db.apache.org/derby/docs/10.7/ref/rrefsqlj41207.html])
> h2. Proposal
> Can these columns not use CLOB-like types as for example as used by
> {{TBLS.VIEW_EXPANDED_TEXT}}? It would seem that suitable type equivalents
> exist for all targeted database platforms:
> * MySQL: {{mediumtext}}
> * Postgres: {{text}}
> * Oracle: {{CLOB}}
> * Derby: {{LONG VARCHAR}}
> I'd suggest that the candidates for type change are:
> * {{COLUMNS_V2.TYPE_NAME}}
> * {{TABLE_PARAMS.PARAM_VALUE}}
> * {{SERDE_PARAMS.PARAM_VALUE}}
> * {{SD_PARAMS.PARAM_VALUE}}
> After updating the maximum length the metastore database needs to be
> configured and restarted with the new settings. Altering {{MAX_STRING_SIZE}}
> will update database objects and possibly invalidate them, as follows:
> * Tables with virtual columns will be updated with new data type metadata for
> virtual columns of {{VARCHAR2(4000)}}, 4000-byte {{NVARCHAR2}}, or
> {{RAW(2000)}} type.
> * Functional indexes will become unusable if a change to their associated
> virtual columns causes the index key to exceed index key length limits.
> Attempts to rebuild such indexes will fail with {{ORA-01450: maximum key
> length exceeded}}.
> * Views will be invalidated if they contain {{VARCHAR2(4000)}}, 4000-byte
> {{NVARCHAR2}}, or {{RAW(2000)}} typed expression columns.
> * Materialized views will be updated with new metadata {{VARCHAR2(4000)}},
> 4000-byte {{NVARCHAR2}}, and {{RAW(2000)}} typed expression columns
> * So the limitation could be raised to 32672 bytes, with the caveat that
> MySQL and SQL Server limit the row length to 65535 bytes, so that should also
> be validated to provide consistency.
> Finally, will this limitation persist in the work resulting from HIVE-9452?
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