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Overview
| Comment: | Minor cleanup of the code in the query planner that computes the costs estimates for the various plans. There are no changes to the costs at this time. But the code is slightly more readable now and that might facilitate future enhancements. |
|---|---|
| Downloads: | Tarball | ZIP archive |
| Timelines: | family | ancestors | descendants | both | trunk |
| Files: | files | file ages | folders |
| SHA1: |
9b4d7226bcee38be5ac68a54bee03b41 |
| User & Date: | drh 2014-03-27 18:36:34.321 |
Context
|
2014-03-28
| ||
| 03:12 | Enhance the sqlite3VdbeRecordCompare() routines so that if they encounter database corruption, they will set the UnpackedRecord.isCorrupt field and return 0. The sqlite3BtreeMovetoUnpacked() routine detects this and returns SQLITE_CORRUPT, causing the corruption to be reported back to the top-level. (check-in: 7fa85eaaaf user: drh tags: trunk) | |
|
2014-03-27
| ||
| 18:36 | Minor cleanup of the code in the query planner that computes the costs estimates for the various plans. There are no changes to the costs at this time. But the code is slightly more readable now and that might facilitate future enhancements. (check-in: 9b4d7226bc user: drh tags: trunk) | |
| 14:05 | Enhance the logest.c utility with new operators: "dup", "inv", "log", and "nlogn". Provide help on an invalid input. (check-in: b4bd2a062c user: drh tags: trunk) | |
Changes
Changes to src/where.c.
| ︙ | ︙ | |||
4324 4325 4326 4327 4328 4329 4330 4331 4332 4333 4334 4335 4336 |
&& (pProbe->szIdxRow<pTab->szTabRow)
&& (pWInfo->wctrlFlags & WHERE_ONEPASS_DESIRED)==0
&& sqlite3GlobalConfig.bUseCis
&& OptimizationEnabled(pWInfo->pParse->db, SQLITE_CoverIdxScan)
)
){
pNew->iSortIdx = b ? iSortIdx : 0;
if( m==0 ){
/* TUNING: Cost of a covering index scan is K*(N + log2(N)).
** + The extra factor K of between 1.1 and 3.0 that depends
** on the relative sizes of the table and the index. K
** is smaller for smaller indices, thus favoring them.
*/
| > > > > > > > < | | | > > > > > > > > > > | | 4324 4325 4326 4327 4328 4329 4330 4331 4332 4333 4334 4335 4336 4337 4338 4339 4340 4341 4342 4343 4344 4345 4346 4347 4348 4349 4350 4351 4352 4353 4354 4355 4356 4357 4358 4359 4360 4361 4362 4363 4364 4365 |
&& (pProbe->szIdxRow<pTab->szTabRow)
&& (pWInfo->wctrlFlags & WHERE_ONEPASS_DESIRED)==0
&& sqlite3GlobalConfig.bUseCis
&& OptimizationEnabled(pWInfo->pParse->db, SQLITE_CoverIdxScan)
)
){
pNew->iSortIdx = b ? iSortIdx : 0;
/* TUNING: The base cost of an index scan is N + log2(N).
** The log2(N) is for the initial seek to the beginning and the N
** is for the scan itself. */
pNew->rRun = sqlite3LogEstAdd(rSize, rLogSize);
if( m==0 ){
/* TUNING: Cost of a covering index scan is K*(N + log2(N)).
** + The extra factor K of between 1.1 and 3.0 that depends
** on the relative sizes of the table and the index. K
** is smaller for smaller indices, thus favoring them.
** The upper bound on K (3.0) matches the penalty factor
** on a full table scan that tries to encourage the use of
** indexed lookups over full scans.
*/
pNew->rRun += 1 + (15*pProbe->szIdxRow)/pTab->szTabRow;
}else{
/* TUNING: The cost of scanning a non-covering index is multiplied
** by log2(N) to account for the binary search of the main table
** that must happen for each row of the index.
** TODO: Should there be a multiplier here, analogous to the 3x
** multiplier for a fulltable scan or covering index scan, to
** further discourage the use of an index scan? Or is the log2(N)
** term sufficient discouragement?
** TODO: What if some or all of the WHERE clause terms can be
** computed without reference to the original table. Then the
** penality should reduce to logK where K is the number of output
** rows.
*/
pNew->rRun += rLogSize;
}
whereLoopOutputAdjust(pWC, pNew);
rc = whereLoopInsert(pBuilder, pNew);
pNew->nOut = rSize;
if( rc ) break;
}
}
|
| ︙ | ︙ | |||
5037 5038 5039 5040 5041 5042 5043 |
nOut = pFrom->nRow + pWLoop->nOut;
maskNew = pFrom->maskLoop | pWLoop->maskSelf;
if( isOrdered<0 ){
isOrdered = wherePathSatisfiesOrderBy(pWInfo,
pWInfo->pOrderBy, pFrom, pWInfo->wctrlFlags,
iLoop, pWLoop, &revMask);
if( isOrdered>=0 && isOrdered<nOrderBy ){
| | > | > > > > | > > > | | | 5053 5054 5055 5056 5057 5058 5059 5060 5061 5062 5063 5064 5065 5066 5067 5068 5069 5070 5071 5072 5073 5074 5075 5076 5077 5078 5079 |
nOut = pFrom->nRow + pWLoop->nOut;
maskNew = pFrom->maskLoop | pWLoop->maskSelf;
if( isOrdered<0 ){
isOrdered = wherePathSatisfiesOrderBy(pWInfo,
pWInfo->pOrderBy, pFrom, pWInfo->wctrlFlags,
iLoop, pWLoop, &revMask);
if( isOrdered>=0 && isOrdered<nOrderBy ){
/* TUNING: Estimated cost of sorting is N*log(N).
** If the order-by clause has X terms but only the last Y terms
** are out of order, then block-sorting will reduce the sorting
** cost to N*log(N)*log(Y/X). The log(Y/X) term is computed
** by rScale.
** TODO: Should the sorting cost get a small multiplier to help
** discourage the use of sorting and encourage the use of index
** scans instead?
*/
LogEst rScale, rSortCost;
assert( nOrderBy>0 );
rScale = sqlite3LogEst((nOrderBy-isOrdered)*100/nOrderBy) - 66;
rSortCost = nRowEst + estLog(nRowEst) + rScale;
/* TUNING: The cost of implementing DISTINCT using a B-TREE is
** also N*log(N) but it has a larger constant of proportionality.
** Multiply by 3.0. */
if( pWInfo->wctrlFlags & WHERE_WANT_DISTINCT ){
rSortCost += 16;
}
WHERETRACE(0x002,
|
| ︙ | ︙ |