Stamatis Zampetakis created HIVE-27755:
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Summary: Quote identifiers in SQL emitted by SchemaTool for MySQL
Key: HIVE-27755
URL: https://issues.apache.org/jira/browse/HIVE-27755
Project: Hive
Issue Type: Improvement
Components: Standalone Metastore
Affects Versions: 4.0.0-beta-1
Reporter: Stamatis Zampetakis
Assignee: Stamatis Zampetakis
Various SchemaTool options/tasks (e.g., "validate") generate and run SQL
statements on the underlying database. Depending on the database identifiers in
the SQL statements may be quoted (see
[https://github.com/apache/hive/blob/2dbfbeefc1a73d6a50f1c829658846fc827fc780/standalone-metastore/metastore-server/src/main/java/org/apache/hadoop/hive/metastore/tools/schematool/HiveSchemaHelper.java#L173]).
Currently, all identifiers are quoted when the database is Postgres and this
tickets aims to do the same for MySQL/MariaDB.
The main motivation behind this change is to avoid unexpected surprises and
query failures when/if the database decides to turn some of the tables/columns
we are using internally to reserved keywords.
As a concrete example, the Percona fork of MySQL recently turned SEQUENCE_TABLE
into a reserved keyword
([https://docs.percona.com/percona-server/8.0/flexibility/sequence_table.html])
and this comes in conflict with our internal metastore table.
The installation scripts do not fail since in that case SEQUENCE_TABLE is
quoted
([https://github.com/apache/hive/blob/2dbfbeefc1a73d6a50f1c829658846fc827fc780/standalone-metastore/metastore-server/src/main/sql/mysql/hive-schema-4.0.0-beta-2.mysql.sql#L447])
but validation queries emitted by the SchemaTool will fail
([https://github.com/apache/hive/blob/2dbfbeefc1a73d6a50f1c829658846fc827fc780/standalone-metastore/metastore-server/src/main/java/org/apache/hadoop/hive/metastore/tools/schematool/SchemaToolTaskValidate.java#L117])
if we don't use quoted identifiers.
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