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Metastore Schema Verification

Hive now records the schema version in the metastore database and verifies that the metastore schema version is compatible hive with Hive binaries that are going to accesss the meatstoremetastore. Note that the hive Hive properties to implicitly create or alter the existing schema are disabled by default. Hive will not attempt to change the metastore schema implicitly. When you execute a hive Hive query against a an old schema, it will fail to access the metastore:

$ build/dist/bin/hive -e "show tables"
FAILED: Execution Error, return code 1 from org.apache.hadoop.hive.ql.exec.DDLTask. java.lang.RuntimeException: Unable to instantiate org.apache.hadoop.hive.metastore.HiveMetaStoreClient

The log will contain an error about version information not found:

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Caused by: MetaException(message:Version information not found in metastore. )
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To suppress the schema check and allow the metastore to implicitly modify the schema, you need to set a configuration property hive.metastore.schema.verification to false in hive-site.xml.

See Hive Metastore Administration for general information about the metastore.

The Hive Schema Tool

The Hive distribution now includes an offline tool for hive Hive metastore schema manipulation. This tool can be used to initialize the metastore schema for the current hive Hive version. It can also handle upgrading the schema from an older version to current. It tries to find the current schema from the metastore if its it is available. This will be applicable to future upgrades like 0.12.0 to 0.13.0. In case of upgrades from older releases like 0.7.0 or 0.10.0, you can specify the schema version of the existing metastore as a command line option to the tool.

The schmeatool schematool figures out the sql SQL scripts required to initialize or upgrade the schema and then execute executes those scripts against the backend database. The metastore DB connection information like JDBC URL, JDBC driver and DB credentials are extracted from the hive Hive configuration. You can provide alternate DB credentials if needed.

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The schematool Command

The schematool command invokes the Hive schema tool with these options:

$ schematool -help
usage: schemaTool
 -dbType <databaseType>             Metastore database type
 -dryRun                            

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List SQL scripts (no execute)
 -help                              

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Print this message
 -info                              Show config and schema details
 -initSchema                        Schema initialization
 -initSchemaTo <initTo>             Schema initialization to a version
 -passWord <password>               Override config file password
 -upgradeSchema                     Schema upgrade
 -upgradeSchemaFrom <upgradeFrom>   Schema upgrade from a version
 -userName <user>                   Override config file user name
 -verbose                           

...

Only print SQL statements

The dbType is required and can be one of:

 derby|mysql|postgres|oracle 

Usage Examples

• Initialize to current schema for a new hive Hive setup:

  No Format
  $ schematool -dbType derby -initSchema Metastore connection URL: jdbc:derby:;databaseName=metastore_db;create=true Metastore Connection Driver : org.apache.derby.jdbc.EmbeddedDriver Metastore connection User: APP Starting metastore schema initialization to 0.13.0 Initialization script hive-schema-0.13.0.derby.sql Initialization script completed schemaTool completeted

• Get schema information:

  No Format
  $ schematool -dbType derby -info Metastore connection URL: jdbc:derby:;databaseName=metastore_db;create=true Metastore Connection Driver : org.apache.derby.jdbc.EmbeddedDriver Metastore connection User: APP Hive distribution version: 0.13.0 Metastore schema version: 0.13.0 schemaTool completeted

• Attempt to get schema information with older metastore:

  No Format
  $ schematool -dbType derby -info Metastore connection URL: jdbc:derby:;databaseName=metastore_db;create=true Metastore Connection Driver : org.apache.derby.jdbc.EmbeddedDriver Metastore connection User: APP Hive distribution version: 0.13.0 org.apache.hadoop.hive.metastore.HiveMetaException: Failed to get schema version. *** schemaTool failed ***

  Since the older metastore dondoesn't store the version informatinformation, the tool reports an error retrieving it.

• Upgrade schema from an 0.10.0 release by specifying the 'from' version:

  No Format

  $ schematool -dbType derby -upgradeSchemaFrom 0.10.0 Metastore connection URL: jdbc:derby:;databaseName=metastore_db;create=true Metastore Connection Driver : org.apache.derby.jdbc.EmbeddedDriver Metastore connection User: APP Starting upgrade metastore schema from version 0.10.0 to 0.13.0 Upgrade script upgrade-0.10.0-to-0.11.0.derby.sql Completed upgrade-0.10.0-to-0.11.0.derby.sql Upgrade script upgrade-0.11.0-to-0.12.0.derby.sql Completed upgrade-0.11.0-to-0.12.0.derby.sql Upgrade script upgrade-0.12.0-to-0.13.0.derby.sql Completed upgrade-0.12.0-to-0.13.0.derby.sql schemaTool completeted

• Upgrade dry run can be used to list the required scripts for the given upgrade.

  No Format

  $ build/dist/bin/schematool -dbType derby -upgradeSchemaFrom 0.7.0 -dryRun Metastore Connection Driver : org.apache.derby.jdbc.EmbeddedDriver Metastore connection User: APP Starting upgrade metastore schema from version 0.7.0 to 0.13.0 Upgrade script upgrade-0.7.0-to-0.8.0.derby.sql Upgrade script upgrade-0.8.0-to-0.9.0.derby.sql Upgrade script upgrade-0.9.0-to-0.10.0.derby.sql Upgrade script upgrade-0.10.0-to-0.11.0.derby.sql Upgrade script upgrade-0.11.0-to-0.12.0.derby.sql Upgrade script upgrade-0.12.0-to-0.13.0.derby.sql schemaTool completeted

  This is useful if you just want to find out all the all required scripts for the schema upgrade.