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| Comment: | Fix long-standing typos in comments. |
|---|---|
| Downloads: | Tarball | ZIP archive | SQL archive |
| Timelines: | family | ancestors | descendants | both | experimental-costs |
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| SHA1: |
b9f91317c34d07769a95dc2f905a6cca |
| User & Date: | drh 2014-04-30 13:19:09 |
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2014-04-30
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| 14:22 | Improved rendering of LogEst values corresponding to real values near 0.0 in the tool/logest.c utility program. (check-in: 32910c8c user: drh tags: experimental-costs) | |
| 13:19 | Fix long-standing typos in comments. (check-in: b9f91317 user: drh tags: experimental-costs) | |
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2014-04-29
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| 19:01 | Test that the default values used when sqlite_stat1 data is not available are calculated correctly. Fixes for the same. (check-in: e2d42f90 user: dan tags: experimental-costs) | |
Changes to src/sqliteInt.h.
521 521 522 522 /* 523 523 ** Estimated quantities used for query planning are stored as 16-bit 524 524 ** logarithms. For quantity X, the value stored is 10*log2(X). This 525 525 ** gives a possible range of values of approximately 1.0e986 to 1e-986. 526 526 ** But the allowed values are "grainy". Not every value is representable. 527 527 ** For example, quantities 16 and 17 are both represented by a LogEst 528 -** of 40. However, since LogEst quantatites are suppose to be estimates, 528 +** of 40. However, since LogEst quantaties are suppose to be estimates, 529 529 ** not exact values, this imprecision is not a problem. 530 530 ** 531 -** "LogEst" is short for "Logarithimic Estimate". 531 +** "LogEst" is short for "Logarithmic Estimate". 532 532 ** 533 533 ** Examples: 534 534 ** 1 -> 0 20 -> 43 10000 -> 132 535 535 ** 2 -> 10 25 -> 46 25000 -> 146 536 536 ** 3 -> 16 100 -> 66 1000000 -> 199 537 537 ** 4 -> 20 1000 -> 99 1048576 -> 200 538 538 ** 10 -> 33 1024 -> 100 4294967296 -> 320
Changes to src/util.c.
1242 1242 if( b>a+49 ) return b; 1243 1243 if( b>a+31 ) return b+1; 1244 1244 return b+x[b-a]; 1245 1245 } 1246 1246 } 1247 1247 1248 1248 /* 1249 -** Convert an integer into a LogEst. In other words, compute a 1250 -** good approximatation for 10*log2(x). 1249 +** Convert an integer into a LogEst. In other words, compute an 1250 +** approximation for 10*log2(x). 1251 1251 */ 1252 1252 LogEst sqlite3LogEst(u64 x){ 1253 1253 static LogEst a[] = { 0, 2, 3, 5, 6, 7, 8, 9 }; 1254 1254 LogEst y = 40; 1255 1255 if( x<8 ){ 1256 1256 if( x<2 ) return 0; 1257 1257 while( x<8 ){ y -= 10; x <<= 1; }