Thread

1. Optimizing GetConflictingVirtualXIDs()

   Simon Riggs <simon@2ndquadrant.com> — 2010-02-14T14:59:22Z

   Optimize GetConflictingVirtualXIDs() in roughly the same manner we
   optimize TransactionIdIsInProgress().
   
   Views?
   
   -- 
    Simon Riggs           www.2ndQuadrant.com
   

2. Re: Optimizing GetConflictingVirtualXIDs()

   Greg Stark <gsstark@mit.edu> — 2010-02-14T17:06:09Z

   On Sun, Feb 14, 2010 at 2:59 PM, Simon Riggs <simon@2ndquadrant.com> wrote:
   > Optimize GetConflictingVirtualXIDs() in roughly the same manner we
   > optimize TransactionIdIsInProgress().
   >
   > Views?
   
   EINSUFFICIENTEXPLANATION :)
   
   
   -- 
   greg
   
   

3. Re: Optimizing GetConflictingVirtualXIDs()

   Simon Riggs <simon@2ndquadrant.com> — 2010-02-14T17:39:28Z

   On Sun, 2010-02-14 at 17:06 +0000, Greg Stark wrote:
   > On Sun, Feb 14, 2010 at 2:59 PM, Simon Riggs <simon@2ndquadrant.com> wrote:
   > > Optimize GetConflictingVirtualXIDs() in roughly the same manner we
   > > optimize TransactionIdIsInProgress().
   > >
   > > Views?
   > 
   > EINSUFFICIENTEXPLANATION :)
   
   ...I like that error code.
   
   
   The patch adds a calculation of RecentGlobalXmin each time it accesses
   the proc array to derive conflicts. It then uses the derived value to
   provide a fast-path out if a potential snapshot conflict arrives that we
   already know will not conflict with any backends. The purpose of this is
   to reduce the number of scans of the procarray and improve the
   performance of the startup process.
   
   The mechanism and purpose is the same as the first check in
   TransactionIdIsInProgress().
   
   -- 
    Simon Riggs           www.2ndQuadrant.com
   
   
   

4. Re: Optimizing GetConflictingVirtualXIDs()

   Tom Lane <tgl@sss.pgh.pa.us> — 2010-02-14T17:45:50Z

   Simon Riggs <simon@2ndQuadrant.com> writes:
   > On Sun, 2010-02-14 at 17:06 +0000, Greg Stark wrote:
   >> EINSUFFICIENTEXPLANATION :)
   
   > ...I like that error code.
   
   I think more EINSUFFICIENTCOMMENTS.  The patch should also add a comment
   to the function, along the lines of "While we have the lock, also update
   RecentGlobalXmin, so that we will have as up-to-date a value as possible
   for next time".  You've also failed to document the meaning or purpose
   of the added output parameter.
   
   			regards, tom lane