MonetDB: default - Better match statements with constants

[mk]

Changeset: 7791d762b01b for MonetDB
URL: http://dev.monetdb.org/hg/MonetDB?cmd=changeset;node=7791d762b01b
Modified Files:
        monetdb5/optimizer/opt_commonTerms.mx
Branch: default
Log Message:

Better match statements with constants
The optimizer built a list based on the last argument in each call.
Mostly this is a variable with limited re-use. However, when it
is a constant value, then there may be another version of it in
the symbol table with a different varid. This means, that
two instruction that match on value were not recognized.

The solution is to keep a single list for all constants
and try the out all. This is based on the assumption that
the number of constants is mostly limited.
It solves the repeatitive occurrences of sql.binds.


diffs (51 lines):

diff --git a/monetdb5/optimizer/opt_commonTerms.mx 
b/monetdb5/optimizer/opt_commonTerms.mx
--- a/monetdb5/optimizer/opt_commonTerms.mx
+++ b/monetdb5/optimizer/opt_commonTerms.mx
@@ -35,6 +35,7 @@
 
 @:exportOptimizer(commonTerms)@
 
+/* #define DEBUG_OPT_COMMONTERMS_MORE */
 #define OPTDEBUGcommonTerms  if ( optDebug & (1 <<DEBUG_OPT_COMMONTERMS) )
 
 #endif
@@ -115,6 +116,9 @@
        int *alias;
        InstrPtr *old;
        int *list;      
+       /* link all final constant expressions in a list */
+       /* it will help to find duplicate sql.bind calls */
+       int cstlist=0;
        int *vars;
 
        (void) cntxt;
@@ -147,10 +151,15 @@
                if ( alias[getArg(p,k)] )
                        getArg(p,k) = alias[getArg(p,k)];
 
-               /* Link the statement to the previous use, based on the first 
argument.*/
+               /* Link the statement to the previous use, based on the last 
argument.*/
                if ( p->retc < p->argc ) {
                        candidate = vars[getArg(p,p->argc-1)];
-                       list[i]= vars[ getArg(p,p->argc-1) ];
+                       if ( isVarConstant(mb, getArg(p,p->argc-1)) ){
+                               /* all instructions with constant tail are 
linked */
+                               list[i] = cstlist;
+                               cstlist = i;
+                       } else
+                               list[i]= vars[ getArg(p,p->argc-1) ];
                        vars[getArg(p,p->argc-1)] = i;
                } else candidate = 0;
 
@@ -188,8 +197,10 @@
                printInstruction(cntxt->fdout, mb, 0, p, LIST_MAL_ALL);
 #endif
                prop = hasSideEffects(p,TRUE) || isUpdateInstruction(p);
+               j =     isVarConstant(mb, getArg(p,p->argc-1))? cstlist: 
candidate;
+                               
                if ( !prop)
-               for (j = candidate; j ; j = list[j]) 
+               for (; j ; j = list[j]) 
                        if ( (q=getInstrPtr(mb,j))->fcn == p->fcn  && 
!isUnsafeFunction(q)){
 #ifdef DEBUG_OPT_COMMONTERMS_MORE
                        mnstr_printf(cntxt->fdout,"#CANDIDATE %d, %d  %d %d ", 
i, j, 
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