diff options
Diffstat (limited to 'src')
-rw-r--r-- | src/analyze.c | 8 |
1 files changed, 7 insertions, 1 deletions
diff --git a/src/analyze.c b/src/analyze.c index e8699653f..39009899a 100644 --- a/src/analyze.c +++ b/src/analyze.c @@ -847,9 +847,14 @@ static void statGet( ** * "WHERE a=? AND b=?" matches 2 rows. ** ** If D is the count of distinct values and K is the total number of - ** rows, then each estimate is computed as: + ** rows, then each estimate is usually computed as: ** ** I = (K+D-1)/D + ** + ** In other words, I is K/D rounded up to the next whole integer. + ** However, if I is between 1.0 and 1.1 (in other words if I is + ** close to 1.0 but just a little larger) then do not round up but + ** instead keep the I value at 1.0. */ sqlite3_str sStat; /* Text of the constructed "stat" line */ int i; /* Loop counter */ @@ -860,6 +865,7 @@ static void statGet( for(i=0; i<p->nKeyCol; i++){ u64 nDistinct = p->current.anDLt[i] + 1; u64 iVal = (p->nRow + nDistinct - 1) / nDistinct; + if( iVal==2 && p->nRow*10 <= nDistinct*11 ) iVal = 1; sqlite3_str_appendf(&sStat, " %llu", iVal); assert( p->current.anEq[i] ); } |