Changeset: b113bfda9b97 for MonetDB
URL: https://dev.monetdb.org/hg/MonetDB?cmd=changeset;node=b113bfda9b97
Modified Files:
monetdb5/optimizer/opt_constants.c
Branch: default
Log Message:
Don't cap the constant table, but cap the look back for matching ones.
In many generated code situations the distance to a previous constant is small.
diffs (39 lines):
diff --git a/monetdb5/optimizer/opt_constants.c
b/monetdb5/optimizer/opt_constants.c
--- a/monetdb5/optimizer/opt_constants.c
+++ b/monetdb5/optimizer/opt_constants.c
@@ -17,6 +17,10 @@
/*
* We have to keep an alias table to reorganize the program
* after the variable stack has changed.
+ * The plan may contain many constants and to check them all would be
quadratic
+ * in the size of the constant list.
+ * The heuristic is to look back into the list only partially.
+ * A hash structure could help out with further reduction.
*/
#include "monetdb_config.h"
#include "mal_instruction.h"
@@ -25,7 +29,7 @@
str
OPTconstantsImplementation(Client cntxt, MalBlkPtr mb, MalStkPtr stk, InstrPtr
p)
{
- int i,k=1, n=0, fnd=0, actions=0;
+ int i, k = 1, n = 0, fnd = 0, actions = 0, limit = 0;
int *alias, *index;
VarPtr x,y, *cst;
char buf[256];
@@ -50,12 +54,13 @@ OPTconstantsImplementation(Client cntxt,
for (i=0; i< mb->vtop; i++)
alias[ i]= i;
- for (i=0; i< mb->vtop && n < 100; i++)
+ for (i=0; i< mb->vtop; i++)
if ( isVarConstant(mb,i) && isVarFixed(mb,i) &&
getVarType(mb,i) != TYPE_ptr){
x= getVar(mb,i);
fnd = 0;
+ limit = n - 128; // don't look to far back
if ( x->type && x->value.vtype)
- for( k= n-1; k>=0; k--){
+ for( k = n-1; k >= 0 && k > limit; k--){
y= cst[k];
if ( x->type == y->type &&
x->rowcnt == y->rowcnt &&
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