firebird/firebird-mirror
firebird/firebird-mirror
8
0
Fork 1
mirror of https://github.com/FirebirdSQL/firebird.git synced 2025-01-24 19:23:02 +01:00
Code Issues

More optimizer adjustments + named constants instead of hardcoded numbers.

Browse Source 
In particular, this commit should resolve the degraded restore performance.
This commit is contained in:
dimitr 2009-08-19 09:18:30 +00:00
parent b8777ae00f
commit 17b630c1fe
2 changed files with 15 additions and 21 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

33
src/jrd/Optimizer.cpp
View File

@ -1702,7 +1702,7 @@ void OptimizerRetrieval::getInversionCandidates(InversionCandidateList* inversio
if (unique && cardinality) if (unique && cardinality)
selectivity = 1 / cardinality; selectivity = 1 / cardinality;
else else
selectivity = MAXIMUM_SELECTIVITY / 10; selectivity = DEFAULT_SELECTIVITY;
} }
InversionCandidate* invCandidate = FB_NEW(pool) InversionCandidate(pool); InversionCandidate* invCandidate = FB_NEW(pool) InversionCandidate(pool);
@ -1949,33 +1949,24 @@ InversionCandidate* OptimizerRetrieval::makeInversion(InversionCandidateList* in
return NULL; return NULL;
} }
const double streamCardinality =
MAX(csb->csb_rpt[stream].csb_cardinality, MINIMUM_CARDINALITY);
// Prepared statements could be optimized against an almost empty table
// and then cached (such as in the restore process), thus causing slowdown
// when the table grows. In this case, let's consider all available indices.
const bool smallTable = (streamCardinality <= THRESHOLD_CARDINALITY);
// This flag disables our smart index selection algorithm. // This flag disables our smart index selection algorithm.
// It's set for any explicit (i.e. user specified) plan which // It's set for any explicit (i.e. user specified) plan which
// requires all existing indices to be considered for a retrieval. // requires all existing indices to be considered for a retrieval.
const bool acceptAll = csb->csb_rpt[stream].csb_plan; // Also, it's set for very small tables (see above).
const bool acceptAll = csb->csb_rpt[stream].csb_plan || smallTable;
double streamCardinality = csb->csb_rpt[stream].csb_cardinality;
// When the cardinality is very small then the statement is being
// prepared on an almost empty table, which would meant no indexes
// will be used at all. The prepared statement could be cached
// (such as in system restore process) and cause slowdown when the
// table grows. Set the cardinality to a value so that at least
// some indexes are chosen.
if (streamCardinality <= 5) {
streamCardinality = 5;
}
double totalSelectivity = MAXIMUM_SELECTIVITY; // worst selectivity double totalSelectivity = MAXIMUM_SELECTIVITY; // worst selectivity
double totalIndexCost = 0; double totalIndexCost = 0;
// Allow indexes also to be used on very small tables. Limit starts // The upper limit to use an index based retrieval is five indexes + almost all datapages
// now above 5 indexes + almost all datapages.
// Also when the table is small and a statement is prepared, but would grow
// while inserting data into this would really slow down the statement.
// An example here is with system tables and the restore process of gbak.
//
// dimitr: TO BE REVIEWED!!!
//
const double maximumCost = (DEFAULT_INDEX_COST * 5) + (streamCardinality * 0.95); const double maximumCost = (DEFAULT_INDEX_COST * 5) + (streamCardinality * 0.95);
const double minimumSelectivity = 1 / streamCardinality; const double minimumSelectivity = 1 / streamCardinality;

3
src/jrd/Optimizer.h
View File

@ -57,7 +57,10 @@ const double REDUCE_SELECTIVITY_FACTOR_EQUALITY = 0.1;
const double REDUCE_SELECTIVITY_FACTOR_INEQUALITY = 0.5; const double REDUCE_SELECTIVITY_FACTOR_INEQUALITY = 0.5;
const double MAXIMUM_SELECTIVITY = 1.0; const double MAXIMUM_SELECTIVITY = 1.0;
const double DEFAULT_SELECTIVITY = 0.1;
const double MINIMUM_CARDINALITY = 1.0; const double MINIMUM_CARDINALITY = 1.0;
const double THRESHOLD_CARDINALITY = 5.0;
// Default (Minimum) cost (nr. of pages) for an index. // Default (Minimum) cost (nr. of pages) for an index.
const int DEFAULT_INDEX_COST = 1; const int DEFAULT_INDEX_COST = 1;