From: Ole John Aske Date: February 23 2011 6:07pm Subject: Re: bzr commit into mysql-5.1-telco-7.0 branch (ole.john.aske:4223) Bug#11804277 List-Archive: http://lists.mysql.com/commits/131970 Message-Id: <4D654CDB.1040708@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit On 23.02.2011 18:00, Jonas Oreland wrote: > Hi OJ, > > 1) What do you think about using heuristic even if we don't have row-count. > E.g if we don't have row-count, set it to 100 and run you range-heuristic anyway Yes, would likely be usefull in those cases. > 2) What do you think about making sure that EQ is preferred over LT even if row-count is low, > so that the divisions don't make estimate the same...if row-count is low... Yes, could be a good idea. That would be something like: if (EQ) return max(E(#rows),2.0); else return max(E(#rows),3.0); Right ? (if It is a completely specified EQuality on PK or Unique key it is always preferred as you suggest. (Fixed by Bug#59517)) Ole John > /Jonas > > On 02/23/11 16:54, Ole John Aske wrote: >> #At file:///net/fimafeng09/export/home/tmp/oleja/mysql/mysql-5.1-telco-7.0/ based on revid:ole.john.aske@stripped >> >> 4223 Ole John Aske 2011-02-23 >> Fix for bug#11804277 - INCORRECT INDEX MAY BE SELECTED DUE TO INSUFFICIENT STATISTICS FROM CLUSTER >> >> Add heuristics to ha_ndbcluster::records_in_range() >> which identifies a range as: >> >> - An open bound range ( LT/GT> - A closed bound range ( BETWEEN AND) >> - A (partial) EQ-range ( EQ) >> >> ... Or a combination of these.... >> >> These are handled as follows: >> >> Open bound ranges >> ----------------- >> Without a histogram of how the values in the index are >> distributed, we can only assume an equal distrubution. >> A statistically correct estimate for a condition of the form >> ' LT/GT' would then have been to assume it selects >> 50% of the rows in the table. However, I have experienced that >> this will cause the range-cost to directly compete with the cost >> of a full table scan. We should therefore be somewhat more >> conservative and estimate 10% of the rows to be returned. >> >> Closed bound range >> ------------------ >> We assume this to be somewhat better than an open bounded range >> returning 5% of the rows in the table. >> >> EQ-range >> -------- >> An EQ-range will excatly specify a fraction of the first part of >> an index. It is reasonable to assume: >> >> - Specifing a larger fraction of the index will improve the >> selectivity of the EQ-range. >> - Each part of the specified EQ-range will have the same >> selectivity. >> >> We can model this as a Binomial Distribution of the indexed >> values. http://en.wikipedia.org/wiki/Binomial_distrib >> >> modified: >> mysql-test/suite/ndb/r/ndb_condition_pushdown.result >> mysql-test/suite/ndb/r/ndb_index.result >> mysql-test/suite/ndb/r/ndb_index_unique.result >> mysql-test/suite/ndb/r/ndb_read_multi_range.result >> mysql-test/suite/ndb/r/ndb_statistics.result >> mysql-test/suite/ndb/t/ndb_statistics.test >> sql/ha_ndbcluster.cc >> === modified file 'mysql-test/suite/ndb/r/ndb_condition_pushdown.result' >> --- a/mysql-test/suite/ndb/r/ndb_condition_pushdown.result 2011-01-17 13:29:52 +0000 >> +++ b/mysql-test/suite/ndb/r/ndb_condition_pushdown.result 2011-02-23 15:54:12 +0000 >> @@ -1910,7 +1910,7 @@ insert into NodeAlias VALUES(null, 8 , ' >> 12:22:26'); >> explain select * from NodeAlias where (aliasKey LIKE '491803%'); >> id select_type table type possible_keys key key_len ref rows Extra >> -1 SIMPLE NodeAlias range NodeAlias_KeyIndex NodeAlias_KeyIndex 48 NULL 10 Using where with pushed condition >> +1 SIMPLE NodeAlias range NodeAlias_KeyIndex NodeAlias_KeyIndex 48 NULL 2 Using where with pushed condition >> select * from NodeAlias where (aliasKey LIKE '491803%') order by id; >> id nodeId displayName aliasKey objectVersion changed >> 7 8 491803% 491803% 0 2008-03-10 12:22:26 >> @@ -2225,7 +2225,7 @@ join tx as t2 on tx.a = t2.c and tx.b = >> where t2.a = 4 >> group by t2.c; >> id select_type table type possible_keys key key_len ref rows filtered Extra >> -1 SIMPLE t2 ref PRIMARY PRIMARY 4 const 10 100.00 Using where; Using filesort >> +1 SIMPLE t2 ref PRIMARY PRIMARY 4 const 2 100.00 Using where; Using filesort >> 1 SIMPLE tx eq_ref PRIMARY PRIMARY 8 test.t2.c,test.t2.d 1 100.00 >> Warnings: >> Note 1003 select `test`.`t2`.`c` AS `c`,count(distinct `test`.`t2`.`a`) AS `count(distinct t2.a)` from `test`.`tx` join `test`.`tx` `t2` where ((`test`.`tx`.`b` = `test`.`t2`.`d`) and (`test`.`tx`.`a` = `test`.`t2`.`c`) and (`test`.`t2`.`a` = 4)) group by `test`.`t2`.`c` >> @@ -2242,7 +2242,7 @@ join tx as t2 on tx.a = t2.c and tx.b = >> where t2.a = 4 >> group by t2.c; >> id select_type table type possible_keys key key_len ref rows filtered Extra >> -1 SIMPLE t2 ref PRIMARY PRIMARY 4 const 10 100.00 Using where; Using filesort >> +1 SIMPLE t2 ref PRIMARY PRIMARY 4 const 2 100.00 Using where; Using filesort >> 1 SIMPLE tx eq_ref PRIMARY PRIMARY 8 test.t2.c,test.t2.d 1 100.00 >> Warnings: >> Note 1003 select `test`.`t2`.`c` AS `c`,count(distinct `test`.`t2`.`a`) AS `count(distinct t2.a)` from `test`.`tx` join `test`.`tx` `t2` where ((`test`.`tx`.`b` = `test`.`t2`.`d`) and (`test`.`tx`.`a` = `test`.`t2`.`c`) and (`test`.`t2`.`a` = 4)) group by `test`.`t2`.`c` >> >> === modified file 'mysql-test/suite/ndb/r/ndb_index.result' >> --- a/mysql-test/suite/ndb/r/ndb_index.result 2010-12-22 11:13:45 +0000 >> +++ b/mysql-test/suite/ndb/r/ndb_index.result 2011-02-23 15:54:12 +0000 >> @@ -306,7 +306,7 @@ explain >> select i,vc from t1 >> where i>=1 or vc> '0'; >> id select_type table type possible_keys key key_len ref rows Extra >> -1 SIMPLE t1 index_merge PRIMARY,i1,i2 i1,i2 5,18 NULL 20 Using sort_union(i1,i2); Using where with pushed condition >> +1 SIMPLE t1 index_merge PRIMARY,i1,i2 i1,i2 5,18 NULL 4 Using sort_union(i1,i2); Using where with pushed condition >> select i,vc from t1 >> where i>=1 or vc> '0'; >> i vc >> @@ -350,7 +350,7 @@ explain >> select i,vc from t2 >> where i>=1 or vc> '0'; >> id select_type table type possible_keys key key_len ref rows Extra >> -1 SIMPLE t2 index_merge i1,i2 i1,i2 5,19 NULL 20 Using sort_union(i1,i2); Using where with pushed condition >> +1 SIMPLE t2 index_merge i1,i2 i1,i2 5,19 NULL 4 Using sort_union(i1,i2); Using where with pushed condition >> select i,vc from t2 >> where i>=1 or vc> '0'; >> i vc >> >> === modified file 'mysql-test/suite/ndb/r/ndb_index_unique.result' >> --- a/mysql-test/suite/ndb/r/ndb_index_unique.result 2011-01-18 07:49:14 +0000 >> +++ b/mysql-test/suite/ndb/r/ndb_index_unique.result 2011-02-23 15:54:12 +0000 >> @@ -185,7 +185,7 @@ set @old_ecpd = @@session.engine_conditi >> set engine_condition_pushdown = true; >> explain select * from t2 where (b = 3 OR b = 5) AND c IS NULL AND a< 9 order by a; >> id select_type table type possible_keys key key_len ref rows Extra >> -1 SIMPLE t2 range PRIMARY,b b 9 NULL 2 Using where with pushed condition; Using filesort >> +1 SIMPLE t2 range PRIMARY,b PRIMARY 4 NULL 2 Using where with pushed condition >> select * from t2 where (b = 3 OR b = 5) AND c IS NULL AND a< 9 order by a; >> a b c >> 3 3 NULL >> >> === modified file 'mysql-test/suite/ndb/r/ndb_read_multi_range.result' >> --- a/mysql-test/suite/ndb/r/ndb_read_multi_range.result 2011-01-18 07:49:14 +0000 >> +++ b/mysql-test/suite/ndb/r/ndb_read_multi_range.result 2011-02-23 15:54:12 +0000 >> @@ -605,7 +605,7 @@ SELECT DISTINCT STRAIGHT_JOIN t1.pk FROM >> t1 LEFT JOIN t2 ON t2.a = t1.a AND t2.pk != 6; >> id select_type table type possible_keys key key_len ref rows Extra >> 1 SIMPLE t1 ALL NULL NULL NULL NULL 3000 Using temporary >> -1 SIMPLE t2 range PRIMARY PRIMARY 4 NULL 20 Using where; Distinct >> +1 SIMPLE t2 range PRIMARY PRIMARY 4 NULL 4 Using where; Distinct >> SELECT DISTINCT STRAIGHT_JOIN t1.pk FROM >> t1 LEFT JOIN t2 ON t2.a = t1.a AND t2.pk != 6; >> drop table t1, t2; >> >> === modified file 'mysql-test/suite/ndb/r/ndb_statistics.result' >> --- a/mysql-test/suite/ndb/r/ndb_statistics.result 2011-01-18 11:49:03 +0000 >> +++ b/mysql-test/suite/ndb/r/ndb_statistics.result 2011-02-23 15:54:12 +0000 >> @@ -38,24 +38,124 @@ id select_type table type possible_keys >> EXPLAIN >> SELECT * FROM t10000 WHERE k>= 42 and k< 10000; >> id select_type table type possible_keys key key_len ref rows Extra >> -1 SIMPLE t10000 range PRIMARY PRIMARY 4 NULL 10 Using where with pushed condition >> +1 SIMPLE t10000 range PRIMARY PRIMARY 4 NULL 500 Using where with pushed condition >> EXPLAIN >> SELECT * FROM t10000 WHERE k BETWEEN 42 AND 10000; >> id select_type table type possible_keys key key_len ref rows Extra >> -1 SIMPLE t10000 range PRIMARY PRIMARY 4 NULL 10 Using where with pushed condition >> +1 SIMPLE t10000 range PRIMARY PRIMARY 4 NULL 500 Using where with pushed condition >> EXPLAIN >> SELECT * FROM t10000 WHERE k< 42; >> id select_type table type possible_keys key key_len ref rows Extra >> -1 SIMPLE t10000 range PRIMARY PRIMARY 4 NULL 10 Using where with pushed condition >> +1 SIMPLE t10000 range PRIMARY PRIMARY 4 NULL 1000 Using where with pushed condition >> EXPLAIN >> SELECT * FROM t10000 WHERE k> 42; >> id select_type table type possible_keys key key_len ref rows Extra >> -1 SIMPLE t10000 range PRIMARY PRIMARY 4 NULL 10 Using where with pushed condition >> +1 SIMPLE t10000 range PRIMARY PRIMARY 4 NULL 1000 Using where with pushed condition >> EXPLAIN >> SELECT * FROM t10000 AS X JOIN t10000 AS Y >> ON Y.I=X.I AND Y.J = X.I; >> id select_type table type possible_keys key key_len ref rows Extra >> 1 SIMPLE X ALL I NULL NULL NULL 10000 >> 1 SIMPLE Y ref J,I I 10 test.X.I,test.X.I 11 Using where >> +EXPLAIN >> +SELECT * FROM t100 WHERE k< 42; >> +id select_type table type possible_keys key key_len ref rows Extra >> +1 SIMPLE t100 range PRIMARY PRIMARY 4 NULL 10 Using where with pushed condition >> +EXPLAIN >> +SELECT * FROM t100 WHERE k> 42; >> +id select_type table type possible_keys key key_len ref rows Extra >> +1 SIMPLE t100 range PRIMARY PRIMARY 4 NULL 10 Using where with pushed condition >> +EXPLAIN >> +SELECT * FROM t10000 WHERE k< 42; >> +id select_type table type possible_keys key key_len ref rows Extra >> +1 SIMPLE t10000 range PRIMARY PRIMARY 4 NULL 1000 Using where with pushed condition >> +EXPLAIN >> +SELECT * FROM t10000 WHERE k> 42; >> +id select_type table type possible_keys key key_len ref rows Extra >> +1 SIMPLE t10000 range PRIMARY PRIMARY 4 NULL 1000 Using where with pushed condition >> +EXPLAIN >> +SELECT * FROM t100 WHERE k BETWEEN 42 AND 10000; >> +id select_type table type possible_keys key key_len ref rows Extra >> +1 SIMPLE t100 range PRIMARY PRIMARY 4 NULL 5 Using where with pushed condition >> +EXPLAIN >> +SELECT * FROM t10000 WHERE k BETWEEN 42 AND 10000; >> +id select_type table type possible_keys key key_len ref rows Extra >> +1 SIMPLE t10000 range PRIMARY PRIMARY 4 NULL 500 Using where with pushed condition >> +EXPLAIN >> +SELECT * FROM t10000 WHERE I = 0; >> +id select_type table type possible_keys key key_len ref rows Extra >> +1 SIMPLE t10000 ref I I 5 const 200 Using where with pushed condition >> +EXPLAIN >> +SELECT * FROM t10000 WHERE J = 0; >> +id select_type table type possible_keys key key_len ref rows Extra >> +1 SIMPLE t10000 ref J J 5 const 100 Using where with pushed condition >> +EXPLAIN >> +SELECT * FROM t10000 WHERE I = 0 AND J = 0; >> +id select_type table type possible_keys key key_len ref rows Extra >> +1 SIMPLE t10000 ref J,I I 10 const,const 4 Using where with pushed condition >> +EXPLAIN >> +SELECT * FROM t10000 WHERE I = 0; >> +id select_type table type possible_keys key key_len ref rows Extra >> +1 SIMPLE t10000 ref I I 5 const 200 Using where with pushed condition >> +EXPLAIN >> +SELECT * FROM t10000 WHERE I = 0 AND J> 1; >> +id select_type table type possible_keys key key_len ref rows Extra >> +1 SIMPLE t10000 range J,I I 10 NULL 100 Using where with pushed condition >> +EXPLAIN >> +SELECT * FROM t10000 WHERE I = 0 AND J< 1; >> +id select_type table type possible_keys key key_len ref rows Extra >> +1 SIMPLE t10000 range J,I I 10 NULL 50 Using where with pushed condition >> +EXPLAIN >> +SELECT * FROM t10000 WHERE I = 0 AND J BETWEEN 1 AND 10; >> +id select_type table type possible_keys key key_len ref rows Extra >> +1 SIMPLE t10000 range J,I I 10 NULL 50 Using where with pushed condition >> +EXPLAIN >> +SELECT * FROM t10000 WHERE I = 0 AND J = 1; >> +id select_type table type possible_keys key key_len ref rows Extra >> +1 SIMPLE t10000 ref J,I I 10 const,const 4 Using where with pushed condition >> +EXPLAIN >> +SELECT * FROM t10000 WHERE J = 0; >> +id select_type table type possible_keys key key_len ref rows Extra >> +1 SIMPLE t10000 ref J J 5 const 100 Using where with pushed condition >> +EXPLAIN >> +SELECT * FROM t10000 WHERE J = 0 AND K> 1; >> +id select_type table type possible_keys key key_len ref rows Extra >> +1 SIMPLE t10000 range PRIMARY,J J 9 NULL 50 Using where with pushed condition >> +EXPLAIN >> +SELECT * FROM t10000 WHERE J = 0 AND K< 1; >> +id select_type table type possible_keys key key_len ref rows Extra >> +1 SIMPLE t10000 range PRIMARY,J J 9 NULL 50 Using where with pushed condition >> +EXPLAIN >> +SELECT * FROM t10000 WHERE J = 0 AND K BETWEEN 1 AND 10; >> +id select_type table type possible_keys key key_len ref rows Extra >> +1 SIMPLE t10000 range PRIMARY,J J 9 NULL 25 Using where with pushed condition >> +EXPLAIN >> +SELECT * FROM t10000 WHERE J = 0 AND K = 1; >> +id select_type table type possible_keys key key_len ref rows Extra >> +1 SIMPLE NULL NULL NULL NULL NULL NULL NULL Impossible WHERE noticed after reading const tables >> +EXPLAIN >> +SELECT * FROM t10000 WHERE I = 0 AND J> 1; >> +id select_type table type possible_keys key key_len ref rows Extra >> +1 SIMPLE t10000 range J,I I 10 NULL 100 Using where with pushed condition >> +EXPLAIN >> +SELECT * FROM t10000 WHERE I> 0 AND J = 1; >> +id select_type table type possible_keys key key_len ref rows Extra >> +1 SIMPLE t10000 ref J,I J 5 const 100 Using where with pushed condition >> +EXPLAIN >> +SELECT * FROM t10000 WHERE I> 0 AND J> 1; >> +id select_type table type possible_keys key key_len ref rows Extra >> +1 SIMPLE t10000 range J,I J 5 NULL 1000 Using where with pushed condition >> +EXPLAIN >> +SELECT * FROM t10000 WHERE J> 1 AND I = 0; >> +id select_type table type possible_keys key key_len ref rows Extra >> +1 SIMPLE t10000 range J,I I 10 NULL 100 Using where with pushed condition >> +EXPLAIN >> +SELECT * FROM t10000 WHERE J = 1 AND I> 0; >> +id select_type table type possible_keys key key_len ref rows Extra >> +1 SIMPLE t10000 ref J,I J 5 const 100 Using where with pushed condition >> +EXPLAIN >> +SELECT * FROM t10000 WHERE J> 1 AND I> 0; >> +id select_type table type possible_keys key key_len ref rows Extra >> +1 SIMPLE t10000 range J,I J 5 NULL 1000 Using where with pushed condition >> DROP TABLE t10,t100,t10000; >> End of 5.1 tests >> >> === modified file 'mysql-test/suite/ndb/t/ndb_statistics.test' >> --- a/mysql-test/suite/ndb/t/ndb_statistics.test 2011-01-18 11:49:03 +0000 >> +++ b/mysql-test/suite/ndb/t/ndb_statistics.test 2011-02-23 15:54:12 +0000 >> @@ -62,6 +62,81 @@ EXPLAIN >> SELECT * FROM t10000 AS X JOIN t10000 AS Y >> ON Y.I=X.I AND Y.J = X.I; >> >> +# >> +# Improved heurists for ::records_in_range() statistics >> +# >> + >> +# Open bounded range should return 10% of #rows in table >> +EXPLAIN >> +SELECT * FROM t100 WHERE k< 42; >> +EXPLAIN >> +SELECT * FROM t100 WHERE k> 42; >> +EXPLAIN >> +SELECT * FROM t10000 WHERE k< 42; >> +EXPLAIN >> +SELECT * FROM t10000 WHERE k> 42; >> + >> +#Closed bounded range should return 5% of #rows in table >> +EXPLAIN >> +SELECT * FROM t100 WHERE k BETWEEN 42 AND 10000; >> +EXPLAIN >> +SELECT * FROM t10000 WHERE k BETWEEN 42 AND 10000; >> + >> +#EQ-range selectivity depends on >> +# - key length specified >> +# - #rows in table. >> +# - unique/non-unique index >> +# - min 2% selectivity >> +# >> +# Possibly combined with open/closed ranges as >> +# above which further improves selectivity >> +# >> +EXPLAIN >> +SELECT * FROM t10000 WHERE I = 0; >> +EXPLAIN >> +SELECT * FROM t10000 WHERE J = 0; >> + >> +EXPLAIN >> +SELECT * FROM t10000 WHERE I = 0 AND J = 0; >> + >> +EXPLAIN >> +SELECT * FROM t10000 WHERE I = 0; >> +EXPLAIN >> +SELECT * FROM t10000 WHERE I = 0 AND J> 1; >> +EXPLAIN >> +SELECT * FROM t10000 WHERE I = 0 AND J< 1; >> +EXPLAIN >> +SELECT * FROM t10000 WHERE I = 0 AND J BETWEEN 1 AND 10; >> +EXPLAIN >> +SELECT * FROM t10000 WHERE I = 0 AND J = 1; >> + >> +EXPLAIN >> +SELECT * FROM t10000 WHERE J = 0; >> +EXPLAIN >> +SELECT * FROM t10000 WHERE J = 0 AND K> 1; >> +EXPLAIN >> +SELECT * FROM t10000 WHERE J = 0 AND K< 1; >> +EXPLAIN >> +SELECT * FROM t10000 WHERE J = 0 AND K BETWEEN 1 AND 10; >> +EXPLAIN >> +SELECT * FROM t10000 WHERE J = 0 AND K = 1; >> + >> +## Verify selection of 'best' index >> +## (The one of index I/J being EQ) >> +EXPLAIN >> +SELECT * FROM t10000 WHERE I = 0 AND J<> 1; >> +EXPLAIN >> +SELECT * FROM t10000 WHERE I<> 0 AND J = 1; >> +EXPLAIN >> +SELECT * FROM t10000 WHERE I<> 0 AND J<> 1; >> + >> +EXPLAIN >> +SELECT * FROM t10000 WHERE J<> 1 AND I = 0; >> +EXPLAIN >> +SELECT * FROM t10000 WHERE J = 1 AND I<> 0; >> +EXPLAIN >> +SELECT * FROM t10000 WHERE J<> 1 AND I<> 0; >> + >> >> DROP TABLE t10,t100,t10000; >> >> >> === modified file 'sql/ha_ndbcluster.cc' >> --- a/sql/ha_ndbcluster.cc 2011-02-18 10:19:20 +0000 >> +++ b/sql/ha_ndbcluster.cc 2011-02-23 15:54:12 +0000 >> @@ -11182,7 +11182,87 @@ ha_ndbcluster::records_in_range(uint inx >> DBUG_RETURN(rows); >> } >> >> - DBUG_RETURN(10); /* Good guess when you don't know anything */ >> + /* Use simple heuristics to estimate fraction >> + of 'stats.record' returned from range. >> + */ >> + if (stats.records != 0&& stats.records != HA_POS_ERROR) >> + { >> + Uint64 rows; >> + Uint64 table_rows= stats.records; >> + size_t min_key_length= (min_key) ? min_key->length : 0; >> + size_t max_key_length= (max_key) ? max_key->length : 0; >> + >> + // Might have an closed/open range bound: >> + // Low range open >> + if (!min_key_length) >> + { >> + rows= (!max_key_length) >> + ? table_rows // No range was specified >> + : table_rows/10; // -oo .. -> 10% selectivity >> + } >> + // High range open >> + else if (!max_key_length) >> + { >> + rows= table_rows/10; //..oo -> 10% selectivity >> + } >> + else >> + { >> + size_t bounds_len= min(min_key_length,max_key_length); >> + uint eq_bound_len= 0; >> + uint eq_bound_offs= 0; >> + >> + KEY_PART_INFO* key_part= key_info->key_part; >> + KEY_PART_INFO* end= key_part+key_info->key_parts; >> + for (; key_part != end; key_part++) >> + { >> + uint part_length= key_part->store_length; >> + if (eq_bound_offs+part_length> bounds_len || >> + memcmp(&min_key->key[eq_bound_offs], >> +&max_key->key[eq_bound_offs], >> + part_length)) >> + { >> + break; >> + } >> + eq_bound_len+= key_part->length; >> + eq_bound_offs+= part_length; >> + } >> + >> + if (!eq_bound_len) >> + { >> + rows= table_rows/20; //.. -> 5% selectivity >> + } >> + else >> + { >> + // Has an equality range on a leading part of 'key_length': >> + // - Null indicator, and HA_KEY_BLOB_LENGTH bytes in >> + // 'extra_length' are removed from key_fraction calculations. >> + // - Assume reduced selectivity for non-unique indexes >> + // by decreasing 'eq_fraction' by 20% >> + // - Assume equal selectivity for all eq_parts in key. >> + >> + double eq_fraction = (double)(eq_bound_len) / >> + (key_length - key_info->extra_length); >> + if (idx_type == ORDERED_INDEX) // Non-unique index -> less selectivity >> + eq_fraction/= 1.20; >> + if (eq_fraction>= 1.0) // Exact match -> 1 row >> + DBUG_RETURN(1); >> + >> + rows = (Uint64)(table_rows / pow(table_rows, eq_fraction)); >> + if (rows> (table_rows/50)) // EQ-range: Max 2% of rows >> + rows= (table_rows/50); >> + >> + if (min_key_length> eq_bound_offs) >> + rows/= 2; >> + if (max_key_length> eq_bound_offs) >> + rows/= 2; >> + } >> + } >> + if (rows< 2) // At least 2 rows as not exact >> + rows= 2; >> + DBUG_RETURN(min(rows,table_rows)); >> + } >> + >> + DBUG_RETURN(10); /* Poor guess when you don't know anything */ >> } >> >> ulonglong ha_ndbcluster::table_flags(void) const >> >> >> >> >> >