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From Rick Hillegas <rick.hille...@oracle.com>
Subject documenting --derby-properties
Date Wed, 07 Aug 2013 18:03:32 GMT
The topic of documenting Derby dash properties is being discussed on 
DERBY-6305. These are the properties which occur in comments in Derby 
queries, prefixed by the comment-initiating string "--derby-properties". 
Some of these properties are documented. Some aren't. Some can be set by 
users. Others can only be set by internal Derby-generated statements. A 
document attached to DERBY-6305 lists these properties together with our 
understanding of how they're used and whether they're described by our 
user docs: DerbyDashProperties.html.

Probably our user docs shouldn't describe the internal properties. The 
wiki can do that.

All of the customer-settable properties appear to be workarounds for 
Derby performance bugs. It's unclear why some of these workarounds are 
documented but others aren't. Possible reasons include:

1) We know how to characterize the performance issues addressed by the 
documented workarounds. Conversely, we can't concisely describe why tech 
support would recommend the undocumented workarounds.

2) We don't care if tech support forgets to file a performance bug after 
recommending a documented workaround. Conversely, we want to make sure 
that we hear about all performance bugs which would be addressed by 
undocumented workarounds.

3) The undocumented, customer-settable Derby dash properties aren't 
really workarounds. Instead, they are debug switches for use by derby-dev.

The documented Derby dash properties are:

   joinOrder
   index
   constraint
   joinStrategy

The undocumented Derby dash properties are:

   useStatistics
   hashIntialCapacity
   hashLoadFactor
   hashMaxCapacity
   bulkFetch

Can anyone shed light on why some of the customer-settable Derby dash 
properties are documented but the others aren't?  This may involve code 
or doc archaeology because some of the workarounds had their own 
Cloudscape-specific syntax; that syntax was deprecated when Derby was 
open-sourced and the workarounds were relegated to --derby-properties 
comments.

Thanks,
-Rick


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