[
https://issues.apache.org/jira/browse/QPID-8245?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16627756#comment-16627756
]
Rob Godfrey commented on QPID-8245:
-----------------------------------
[~alex.rufous] My assumption is that it will be quicker to "skip" than to
decode a value, and that the only time on the critical path where
get(<propertyname>) will ever be called will be on the filtering code, and that
in all other cases (such as converting a message to a different protocol, or
displaying the headers in the console) we can ignore the overhead of completely
re-decoding... so the code would look something like this:
{code}
private static final Object NOT_PRESENT = new Object();
public Object get(String key)
{
Object value = _cached.get(key);
if(value == null)
{
value = findValueForKey(key);
_cached.putIfAbsent(key, value);
}
return value == NOT_PRESENT ? null : value;
}
private Object findValueForKey(key)
{
AMQShortString keyAsShortString = AMQShortString.valueOf(key);
QpidByteBuffer dup = _encodedForm.duplicate();
while(dup.hasRemaining())
{
if(nextKeyEquals(dup, keyAsShortString)
{
AMQTypedValue value = AMQTypedValue.readFromBuffer(slice);
return value.getValue();
}
else
{
skipValue(dup);
}
}
return NOT_PRESENT;
}
{code}
> [Broker-J] [AMQP 0-8..0-91] Decode FiledTable fields on demand
> --------------------------------------------------------------
>
> Key: QPID-8245
> URL: https://issues.apache.org/jira/browse/QPID-8245
> Project: Qpid
> Issue Type: Improvement
> Components: Broker-J
> Affects Versions: qpid-java-broker-7.1.0
> Reporter: Alex Rudyy
> Priority: Major
> Fix For: qpid-java-broker-7.1.0
>
> Attachments:
> 0001-QPID-8245-Broker-J-Stop-rellocating-message-headers-.patch,
> 0002-QPID-8245-Add-factory-methods-to-create-field-table-.patch,
> 0003-QPID-8245-Remove-FiledTable-setters-methods-modifyin.patch,
> 0004-QPID-8245-Decode-field-table-properties-when-require.patch,
> 0005-QPID-8245-Remove-methods-getXXX-in-order-to-simplify.patch,
> 0005-QPID-8245-Split-field-table-into-2-implementations.patch
>
>
> At the moment all field table properties are decoded when decode
> functionality is invoked. For use cases when only some of the field table
> properties are queried, the decoding functionality can be changed to stop
> decoding on getting the requested property. Potentially, such approach can
> improve the performance of routing transient messages when destinations are
> bound to the routing exchange using selector filters. As filter expression
> contains only some properties, the decoding of message headers can be stopped
> on getting all fields specified in selector expression.
> The idea is illustrated by Rob Godfrey on
> [QPID-8238|https://issues.apache.org/jira/browse/QPID-8238?focusedCommentId=16601936&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-16601936]
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