Stephen Allen created JENA-568:
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Summary: Improve Fuseki/TDB transaction memory usage
Key: JENA-568
URL: https://issues.apache.org/jira/browse/JENA-568
Project: Apache Jena
Issue Type: Improvement
Components: TDB
Reporter: Stephen Allen
Assignee: Stephen Allen
TDB has to buffer in memory all of the modified blocks for a transaction before
committing it. This causes out of memory exceptions when attempting to add a
large number of statements in a single transaction.
An easy way to fix this would be to copy the write block contents into a memory
mapped file instead of heap memory ^†^. We can provide three user specified
options for controlling the location of the temporary blocks:
# JVM heap (default, and what we currently use)
# Direct memory (process heap, but not in the JVM)
# Memory mapped temporary file
See this [Jena thread| http://markmail.org/thread/ckeevvhl2luevixw] for some
additional discussion.
^†^ _The harder way would involve writing the old blocks to the journal, then
writing the new blocks directly to the indexes, with a tombstone pointing to
the old block in the journal so that readers could still retrieve the old
version. This however would seem to require a substantial refactor, as well as
a change to the on-disk database format._
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