About
Schema tool helps to initialise and upgrade metastore database and hive sys schema.
Metastore Schema Verification
Hive records the schema version in the metastore database and verifies that the metastore schema version is compatible with Hive binaries that are going to access the metastore. Note that the 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 query against 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:
... Caused by: MetaException(message:Version information not found in metastore. ) ...
By default the configuration property metastore.schema.verification is true. If we set it false, metastore implicitly writes the schema version if it's not matching. To disable the strict schema verification, you need to set this property 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 metastore schema manipulation. This tool can be used to initialize the metastore schema for the current 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 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 schematool
figures out the SQL scripts required to initialize or upgrade the schema and then 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 configuration. You can provide alternate DB credentials if needed.
Warning: You should always initialize the metastore schema first and the Hive schema second. The Hive schema initialization checks the metastore database schema and if it is not initialized, it puts some objects into the metastore database as well to make sure hive schema is running. That also means if you want to run the metastore schema initialization after the hive one, it will fail as it finds a database that already contains some objects.
The schematool
Command
The schematool
command invokes the Hive schema tool with these options:
$ schematool -help usage: schemaTool -dbType <databaseType> Metastore database type -driver <driver> Driver name for connection -dryRun List SQL scripts (no execute) -help Print this message -info Show config and schema details -initSchema Schema initialization -initSchemaTo <initTo> Schema initialization to a version -metaDbType <metaDatabaseType> Used only if upgrading the system catalog for hive -passWord <password> Override config file password -upgradeSchema Schema upgrade -upgradeSchemaFrom <upgradeFrom> Schema upgrade from a version -url <url> Connection url to the database -userName <user> Override config file user name -verbose Only print SQL statements (Additional catalog related options added in Hive 3.0.0 (HIVE-19135] release are below. -createCatalog <catalog> Create catalog with given name -catalogLocation <location> Location of new catalog, required when adding a catalog -catalogDescription <description> Description of new catalog -ifNotExists If passed then it is not an error to create an existing catalog -moveDatabase <database> Move a database between catalogs. All tables under it would still be under it as part of new catalog. Argument is the database name. Requires --fromCatalog and --toCatalog parameters as well -moveTable <table> Move a table to a different database. Argument is the table name. Requires --fromCatalog, --toCatalog, --fromDatabase, and --toDatabase -toCatalog <catalog> Catalog a moving database or table is going to. This is required if you are moving a database or table. -fromCatalog <catalog> Catalog a moving database or table is coming from. This is required if you are moving a database or table. -toDatabase <database> Database a moving table is going to. This is required if you are moving a table. -fromDatabase <database> Database a moving table is coming from. This is required if you are moving a table.
The dbType is required and can be one of:
derby|mysql|postgres|oracle|mssql
Version
The dbType "mssql
" was added in Hive 0.13.1 with HIVE-6862.
Usage Examples
Initialize to current schema for a new Hive setup:
$ 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 completed
Get schema information:
$ 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 completed
Attempt to get schema information with older metastore:
$ 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 doesn't store the version information, the tool reports an error retrieving it.
Upgrade schema from an 0.10.0 release by specifying the 'from' version:
$ 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 completed
Upgrade dry run can be used to list the required scripts for the given upgrade.
$ 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 completed
This is useful if you just want to find out all the required scripts for the schema upgrade.
Moving a database and tables under it from default Hive catalog to a custom spark catalog
build/dist/bin/schematool -moveDatabase db1 -fromCatalog hive -toCatalog spark
Moving a table from Hive catalog to Spark Catalog
# Create the desired target database in spark catalog if it doesn't already exist. beeline ... -e "create database if not exists newdb"; schematool -moveDatabase newdb -fromCatalog hive -toCatalog spark # Now move the table to target db under the spark catalog. schematool -moveTable table1 -fromCatalog hive -toCatalog spark -fromDatabase db1 -toDatabase newdb