Activity - extractPhysicalSchema

Activity Type: Relational

Description

Retrieve physical metadata from a database, such as table sizes and row counts.

Examples

<extractPhysicalSchema name="extract">
  <output name="schema">
</extractPhysicalSchema>

<extractPhysicalSchema name="extract">
  <getTables name="littleblackbook">
  <output name="schema">
</extractPhysicalSchema>

Specification

Element extractPhysicalSchema:

• Attribute name - unique name for the activity within the scope of a request.
• Element getTables (optional) - retrieve the physical schema for a specified table only
  • Attribute name (required) - the name of a table
• Element output (required) - output stream.
  • Attribute name - name of the activity's output stream.

Data Resource Accessor

This activity requires a data resource accessor that implements the following interface: uk.org.ogsadai.dataresource.JDBCConnectionProvider

XML Schema

OGSA-DAI/schema/ogsadai/xsd/activities/extract_database_schema.xsd

Classes

Implementations of this activity are database specific. The table below lists supported databases and corresponding classes for dynamically extracting the physical schema.

Alternatively, physical schema information may be provided by the service deployer in a static way. The following implementation loads a physical schema from a configuration file:

uk.org.ogsadai.activity.relational.PhysicalSchemaFileActivity

This implementation is actually independent of the type of data resource and does not require a specific data resource accessor. However, the resulting physical schema provides information on tables, rows and indexes.

Configuration

When deploying the PhysicalSchemaFileActivity implementation the physical schema will not be extracted dynamically but is provided in a static way. This can be used, for example, if the database is not supported by the dynamic extractors or if dynamic extraction would be too costly. The static information is provided in a configuration file for the activity. The location of the configuration file is specified in the activity configuration document.

For example:

<database name="ogsadai" maxJoinSize="23234" joinBufferSize="99999">
  <table name="littleblackbook"
         dataLength="100000" 
         indexLength="0" 
         avgRowLength="124" 
         rowCount="10000" 
         rowFormat="Compressed"/>
</database>

Element database - root element of the configuration:

• Attribute name - name of the database
• Attribute maxJoinSize - maximum number of rows that are accessed when executing a select or join statement
• Attribute joinBufferSize - size of the buffer that is used for full joins
• Element table - specifies the name of a table and physical metadata for this table
  • Attribute name - name of the table
  • Attribute dataLength - size of the table in bytes
  • Attribute indexLength - size of the table index in bytes.
  • Attribute avgRowLength - average row length
  • Attribute rowCount - number of rows
  • Attribute rowFormat - row storage format (database specific)

NOTE: For implementations that extract metadata dynamically (see above for supported databases) a configuration file need not be provided.

Client Toolkit Class

uk.org.ogsadai.client.toolkit.activity.relational.ExtractDatabaseSchema