Thread

1. [PATCH] Replace a long chain of if's in eval_const_expressions_mutator by a switch()

   Andres Freund <andres@anarazel.de> — 2011-11-18T20:13:25Z

   Hi,
   
   While playing around with writing a newer allocator last week (using a 
   somewhat slab allocator alike architecture) I found 
   eval_const_expressions_mutator to be surprisingly high in profiles.
   
   For unknown reasons the function used non chained ifs for every handled
   nodeType.
   
   Replacing the if chain with if; else if; ... resulted in a small
   speedup. Replacing it with a switch() in a bigger one.
   
   When testing with a statement containing a longer VALUES statement:
   pgbench -M prepared -f stmt -T 10:
   orig: 10015.28
   if: 10075.48
   switch: 10246.52
   
   Thats a 2.3% increase over several runs. Other statements yielded smaller but 
   all positive results.
   
   As far as I can see there currently is no point for writing the function as it 
   is right now. Am I missing something?
   
   Andres
   
   

2. Re: [PATCH] Replace a long chain of if's in eval_const_expressions_mutator by a switch()

   Tom Lane <tgl@sss.pgh.pa.us> — 2011-11-18T21:14:22Z

   Andres Freund <andres@anarazel.de> writes:
   > For unknown reasons the function used non chained ifs for every handled
   > nodeType.
   > Replacing the if chain with if; else if; ... resulted in a small
   > speedup. Replacing it with a switch() in a bigger one.
   
   Cool, but this patch is impossible to validate by eye.  Could you
   resubmit a version that doesn't reindent unchanged code?  Leave it
   for pgindent to clean that up later.
   
   			regards, tom lane
   
   

3. Re: [PATCH] Replace a long chain of if's in eval_const_expressions_mutator by a switch()

   Andres Freund <andres@anarazel.de> — 2011-11-18T21:45:31Z

   On Friday, November 18, 2011 10:14:22 PM Tom Lane wrote:
   > Andres Freund <andres@anarazel.de> writes:
   > > For unknown reasons the function used non chained ifs for every handled
   > > nodeType.
   > > Replacing the if chain with if; else if; ... resulted in a small
   > > speedup. Replacing it with a switch() in a bigger one.
   > 
   > Cool, but this patch is impossible to validate by eye.  Could you
   > resubmit a version that doesn't reindent unchanged code?  Leave it
   > for pgindent to clean that up later.
   Sure. It was just to confusing reading the code without reindenting.
   
   Btw, I found git diff/show/blame -w very useful to view reindent code.
   
   Actually git show -w seems to produce an applyable patch which doesn't 
   reindent...
   
   Andres
   

4. Re: [PATCH] Replace a long chain of if's in eval_const_expressions_mutator by a switch()

   Tom Lane <tgl@sss.pgh.pa.us> — 2011-11-28T19:23:58Z

   Andres Freund <andres@anarazel.de> writes:
   > On Friday, November 18, 2011 10:14:22 PM Tom Lane wrote:
   >> Andres Freund <andres@anarazel.de> writes:
   >>> Replacing the if chain with if; else if; ... resulted in a small
   >>> speedup. Replacing it with a switch() in a bigger one.
   
   >> Cool, but this patch is impossible to validate by eye.  Could you
   >> resubmit a version that doesn't reindent unchanged code?  Leave it
   >> for pgindent to clean that up later.
   
   > Sure. It was just to confusing reading the code without reindenting.
   > Btw, I found git diff/show/blame -w very useful to view reindent code.
   
   Applied, thanks.  Bruce, would you mind running pgindent on
   just src/backend/optimizer/util/clauses.c ?  That seems safer than
   reindenting manually.
   
   			regards, tom lane
   
   

5. Re: [PATCH] Replace a long chain of if's in eval_const_expressions_mutator by a switch()

   Bruce Momjian <bruce@momjian.us> — 2011-11-28T21:47:52Z

   Tom Lane wrote:
   > Andres Freund <andres@anarazel.de> writes:
   > > On Friday, November 18, 2011 10:14:22 PM Tom Lane wrote:
   > >> Andres Freund <andres@anarazel.de> writes:
   > >>> Replacing the if chain with if; else if; ... resulted in a small
   > >>> speedup. Replacing it with a switch() in a bigger one.
   > 
   > >> Cool, but this patch is impossible to validate by eye.  Could you
   > >> resubmit a version that doesn't reindent unchanged code?  Leave it
   > >> for pgindent to clean that up later.
   > 
   > > Sure. It was just to confusing reading the code without reindenting.
   > > Btw, I found git diff/show/blame -w very useful to view reindent code.
   > 
   > Applied, thanks.  Bruce, would you mind running pgindent on
   > just src/backend/optimizer/util/clauses.c ?  That seems safer than
   > reindenting manually.
   
   Done.
   
   -- 
     Bruce Momjian  <bruce@momjian.us>        http://momjian.us
     EnterpriseDB                             http://enterprisedb.com
   
     + It's impossible for everything to be true. +