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http://objectstyle.org/jira/secure/ViewIssue.jspa?key=CAY-222
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Key: CAY-222
Summary: Change CREATE statement for HSQLDB when Generating SQL
Type: Improvement
Status: Assigned
Priority: Minor
Project: Cayenne
Components:
CayenneModeler GUI
Assignee: Andrus Adamchik
Reporter: Michael Gentry
Created: Fri, 29 Oct 2004 9:49 AM
Updated: Fri, 29 Oct 2004 9:49 AM
Environment: All environments.
Description:
When generating SQL for HSQLDB in the Modeler, table creation is specified as:
CREATE TABLE ...
when it should most likely be:
CREATE CACHED TABLE ...
In HSQLDB, the default version is a "memory" table, which means all data for the table is in memory (even if it is writing through to the disk as INSERT statements). The "cached" table only keeps a portion of the table/indexes in memory, which allows for much larger tables (yes, the terminology is confusing since it seems that the cached table would be kept in memory).
To quote the documentation:
Memory tables are the default type when the CREATE TABLE command is used. Their data is held entirely in memory but any change to their structure or contents is written to the <dbname>.script file. The script file is read the next time the database is opened, and the MEMORY tables are recreated with all their contents. So unlike TEMP table, the default, MEMORY tables are persistent.
CACHED tables are created with the CREATE CACHED TABLE command. Only part of their data or indexes is held in memory, allowing large tables that would otherwise take up to several hundred megabytes of memory. Another advantage of cached tables is that the database engine takes less time to start up when a cached table is used for large amounts of data. The disadvantage of cached tables is a reduction in speed. Do not use cached tables if your data set is relatively small. In an application with some small tables and some large ones, it is better to use the default, MEMORY mode for the small tables.
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This archive was generated by hypermail 2.0.0 : Fri Oct 29 2004 - 09:49:49 EDT