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Experimental support for speeding up CREATE INDEX commands using an offline merge sort.

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FossilOrigin-Name: 30dbf0feab0323250404e0741ac2716bcb6b0cbe
This commit is contained in:
dan
2011-07-12 14:28:05 +00:00
parent 80084ca8e8
commit a20fde64eb
9 changed files with 685 additions and 28 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/build.c
+19 -2
View File
@@ -2308,6 +2308,7 @@ static void sqlite3RefillIndex(Parse *pParse, Index *pIndex, int memRootPage){
Table *pTab = pIndex->pTable; /* The table that is indexed */
int iTab = pParse->nTab++; /* Btree cursor used for pTab */
int iIdx = pParse->nTab++; /* Btree cursor used for pIndex */
int iSorter = pParse->nTab++; /* Btree cursor used for sorting */
int addr1; /* Address of top of loop */
int tnum; /* Root page of index */
Vdbe *v; /* Generate code into this virtual machine */
@@ -2341,10 +2342,24 @@ static void sqlite3RefillIndex(Parse *pParse, Index *pIndex, int memRootPage){
if( memRootPage>=0 ){
sqlite3VdbeChangeP5(v, 1);
}
/* Open the sorter cursor. */
sqlite3VdbeAddOp4(v, OP_OpenSorter, iSorter, 0, 0, (char*)pKey, P4_KEYINFO);
/* Open the table. Loop through all rows of the table, inserting index
** records into the sorter. */
sqlite3OpenTable(pParse, iTab, iDb, pTab, OP_OpenRead);
addr1 = sqlite3VdbeAddOp2(v, OP_Rewind, iTab, 0);
regRecord = sqlite3GetTempReg(pParse);
regIdxKey = sqlite3GenerateIndexKey(pParse, pIndex, iTab, regRecord, 1);
sqlite3VdbeAddOp2(v, OP_IdxInsert, iSorter, regRecord);
sqlite3VdbeAddOp2(v, OP_Next, iTab, addr1+1);
sqlite3VdbeJumpHere(v, addr1);
/* Rewind the sorter. Loop through index records in sorted order. */
addr1 = sqlite3VdbeAddOp2(v, OP_Rewind, iSorter, 0);
sqlite3VdbeAddOp2(v, OP_RowKey, iSorter, regRecord);
if( pIndex->onError!=OE_None ){
const int regRowid = regIdxKey + pIndex->nColumn;
const int j2 = sqlite3VdbeCurrentAddr(v) + 2;
@@ -2363,12 +2378,14 @@ static void sqlite3RefillIndex(Parse *pParse, Index *pIndex, int memRootPage){
sqlite3HaltConstraint(
pParse, OE_Abort, "indexed columns are not unique", P4_STATIC);
}
sqlite3VdbeAddOp2(v, OP_IdxInsert, iIdx, regRecord);
sqlite3VdbeAddOp3(v, OP_IdxInsert, iIdx, regRecord, 1);
sqlite3VdbeChangeP5(v, OPFLAG_USESEEKRESULT);
sqlite3ReleaseTempReg(pParse, regRecord);
sqlite3VdbeAddOp2(v, OP_Next, iTab, addr1+1);
sqlite3VdbeAddOp2(v, OP_Next, iSorter, addr1+1);
sqlite3VdbeJumpHere(v, addr1);
sqlite3VdbeAddOp1(v, OP_Close, iTab);
sqlite3VdbeAddOp1(v, OP_Close, iSorter);
sqlite3VdbeAddOp1(v, OP_Close, iIdx);
}
src/vdbe.c
+34 -12
View File
@@ -3144,6 +3144,7 @@ case OP_OpenWrite: {
** by this opcode will be used for automatically created transient
** indices in joins.
*/
case OP_OpenSorter:
case OP_OpenAutoindex:
case OP_OpenEphemeral: {
VdbeCursor *pCx;
@@ -3154,12 +3155,14 @@ case OP_OpenEphemeral: {
SQLITE_OPEN_DELETEONCLOSE |
SQLITE_OPEN_TRANSIENT_DB;
int btflags = BTREE_OMIT_JOURNAL | pOp->p5;
if( pOp->opcode!=OP_OpenSorter ) btflags |= BTREE_SINGLE;
assert( pOp->p1>=0 );
pCx = allocateCursor(p, pOp->p1, pOp->p2, -1, 1);
if( pCx==0 ) goto no_mem;
pCx->nullRow = 1;
rc = sqlite3BtreeOpen(db->pVfs, 0, db, &pCx->pBt,
BTREE_OMIT_JOURNAL | BTREE_SINGLE | pOp->p5, vfsFlags);
rc = sqlite3BtreeOpen(db->pVfs, 0, db, &pCx->pBt, btflags, vfsFlags);
if( rc==SQLITE_OK ){
rc = sqlite3BtreeBeginTrans(pCx->pBt, 1);
}
@@ -3178,7 +3181,7 @@ case OP_OpenEphemeral: {
rc = sqlite3BtreeCursor(pCx->pBt, pgno, 1,
(KeyInfo*)pOp->p4.z, pCx->pCursor);
pCx->pKeyInfo = pOp->p4.pKeyInfo;
pCx->pKeyInfo->enc = ENC(p->db);
pCx->pKeyInfo->enc = ENC(db);
}
pCx->isTable = 0;
}else{
@@ -3188,6 +3191,9 @@ case OP_OpenEphemeral: {
}
pCx->isOrdered = (pOp->p5!=BTREE_UNORDERED);
pCx->isIndex = !pCx->isTable;
if( rc==SQLITE_OK && pOp->opcode==OP_OpenSorter ){
rc = sqlite3VdbeSorterInit(db, pCx);
}
break;
}
@@ -4077,6 +4083,12 @@ case OP_RowData: {
assert( pC!=0 );
assert( pC->nullRow==0 );
assert( pC->pseudoTableReg==0 );
if( pC->pSorter ){
rc = sqlite3VdbeSorterRowkey(db, pC, pOut);
break;
}
assert( pC->pCursor!=0 );
pCrsr = pC->pCursor;
assert( sqlite3BtreeCursorIsValid(pCrsr) );
@@ -4257,7 +4269,9 @@ case OP_Rewind: { /* jump */
pC = p->apCsr[pOp->p1];
assert( pC!=0 );
res = 1;
if( (pCrsr = pC->pCursor)!=0 ){
if( pC->pSorter ){
rc = sqlite3VdbeSorterRewind(db, pC, &res);
}else if( (pCrsr = pC->pCursor)!=0 ){
rc = sqlite3BtreeFirst(pCrsr, &res);
pC->atFirst = res==0 ?1:0;
pC->deferredMoveto = 0;
@@ -4311,17 +4325,23 @@ case OP_Next: { /* jump */
if( pC==0 ){
break; /* See ticket #2273 */
}
pCrsr = pC->pCursor;
if( pCrsr==0 ){
pC->nullRow = 1;
break;
if( pC->pSorter ){
assert( pOp->opcode==OP_Next );
rc = sqlite3VdbeSorterNext(db, pC, &res);
}else{
pCrsr = pC->pCursor;
if( pCrsr==0 ){
pC->nullRow = 1;
break;
}
res = 1;
assert( pC->deferredMoveto==0 );
rc = pOp->opcode==OP_Next ? sqlite3BtreeNext(pCrsr, &res) :
sqlite3BtreePrevious(pCrsr, &res);
}
res = 1;
assert( pC->deferredMoveto==0 );
rc = pOp->opcode==OP_Next ? sqlite3BtreeNext(pCrsr, &res) :
sqlite3BtreePrevious(pCrsr, &res);
pC->nullRow = (u8)res;
pC->cacheStatus = CACHE_STALE;
if( res==0 ){
pc = pOp->p2 - 1;
if( pOp->p5 ) p->aCounter[pOp->p5-1]++;
@@ -4354,6 +4374,8 @@ case OP_IdxInsert: { /* in2 */
assert( pOp->p1>=0 && pOp->p1<p->nCursor );
pC = p->apCsr[pOp->p1];
assert( pC!=0 );
rc = sqlite3VdbeSorterWrite(db, pC);
if( rc!=SQLITE_OK ) goto abort_due_to_error;
pIn2 = &aMem[pOp->p2];
assert( pIn2->flags & MEM_Blob );
pCrsr = pC->pCursor;
src/vdbeInt.h
+8
View File
@@ -30,6 +30,9 @@ typedef struct VdbeOp Op;
*/
typedef unsigned char Bool;
/* Opaque type used by code in vdbesort.c */
typedef struct VdbeSorter VdbeSorter;
/*
** A cursor is a pointer into a single BTree within a database file.
** The cursor can seek to a BTree entry with a particular key, or
@@ -61,6 +64,7 @@ struct VdbeCursor {
i64 seqCount; /* Sequence counter */
i64 movetoTarget; /* Argument to the deferred sqlite3BtreeMoveto() */
i64 lastRowid; /* Last rowid from a Next or NextIdx operation */
VdbeSorter *pSorter; /* Sorter object for OP_OpenSorter cursors */
/* Result of last sqlite3BtreeMoveto() done by an OP_NotExists or
** OP_IsUnique opcode on this cursor. */
@@ -388,6 +392,10 @@ void sqlite3VdbeFrameDelete(VdbeFrame*);
int sqlite3VdbeFrameRestore(VdbeFrame *);
void sqlite3VdbeMemStoreType(Mem *pMem);
int sqlite3VdbeSorterInit(sqlite3 *, VdbeCursor *);
int sqlite3VdbeSorterWrite(sqlite3 *, VdbeCursor *);
void sqlite3VdbeSorterClose(sqlite3 *, VdbeCursor *);
#if !defined(SQLITE_OMIT_SHARED_CACHE) && SQLITE_THREADSAFE>0
void sqlite3VdbeEnter(Vdbe*);
void sqlite3VdbeLeave(Vdbe*);
src/vdbeaux.c
+1
View File
@@ -1565,6 +1565,7 @@ void sqlite3VdbeFreeCursor(Vdbe *p, VdbeCursor *pCx){
if( pCx==0 ){
return;
}
sqlite3VdbeSorterClose(p->db, pCx);
if( pCx->pBt ){
sqlite3BtreeClose(pCx->pBt);
/* The pCx->pCursor will be close automatically, if it exists, by
src/vdbesort.c
+533
View File
@@ -0,0 +1,533 @@
/*
** 2011 July 9
**
** The author disclaims copyright to this source code. In place of
** a legal notice, here is a blessing:
**
** May you do good and not evil.
** May you find forgiveness for yourself and forgive others.
** May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains code for the VdbeSorter object, used in concert with
** a VdbeCursor to sort large numbers of keys (as may be required, for
** example, by CREATE INDEX statements on tables too large to fit in main
** memory).
*/
#include "sqliteInt.h"
#include "vdbeInt.h"
typedef struct VdbeSorterIter VdbeSorterIter;
/*
** The aIter[] and aTree[] arrays are used to iterate through the sorter
** contents after it has been populated. To iterate through the sorter
** contents, the contents of the nRoot b-trees must be incrementally merged.
**
** The first nRoot elements of the aIter[] array contain cursors open
** on each of the b-trees. An aIter[] element either points to a valid
** key or else is at EOF. For the purposes of the paragraphs below, we
** assume that the array is actually N elements in size, where N is the
** smallest power of 2 greater to or equal to nRoot. The extra aIter[]
** elements are treated as if they are empty trees (always at EOF).
**
** The aTree[] array is N elements in size. The value of N is stored in
** the VdbeSorter.nTree variable.
**
** The final (N/2) elements of aTree[] contain the results of comparing
** pairs of iterator keys together. Element i contains the result of
** comparing aIter[2*i-N] and aIter[2*i-N+1]. Whichever key is smaller, the
** aTree element is set to the index of it.
**
** For the purposes of this comparison, EOF is considered greater than any
** other key value. If the keys are equal (only possible with two EOF
** values), it doesn't matter which index is stored.
**
** The (N/4) elements of aTree[] that preceed the final (N/2) described
** above contains the index of the smallest of each block of 4 iterators.
** And so on. So that aTree[1] contains the index of the iterator that
** currently points to the smallest key value. aTree[0] is unused.
**
** Example:
**
** aIter[0] -> Banana
** aIter[1] -> Feijoa
** aIter[2] -> Elderberry
** aIter[3] -> Currant
** aIter[4] -> Grapefruit
** aIter[5] -> Apple
** aIter[6] -> Durian
** aIter[7] -> EOF
**
** aTree[] = { X, 5 0, 5 0, 3, 5, 6 }
**
** The current element is "Apple" (the value of the key indicated by
** iterator 5). When the Next() operation is invoked, iterator 5 will
** be advanced to the next key in its segment. Say the next key is
** "Eggplant":
**
** aIter[5] -> Eggplant
**
** The contents of aTree[] are updated first by comparing the new iterator
** 5 key to the current key of iterator 4 (still "Grapefruit"). The iterator
** 5 value is still smaller, so aTree[6] is set to 5. And so on up the tree.
** The value of iterator 6 - "Durian" - is now smaller than that of iterator
** 5, so aTree[3] is set to 6. Key 0 is smaller than key 6 (Banana<Durian),
** so the value written into element 1 of the array is 0. As follows:
**
** aTree[] = { X, 0 0, 6 0, 3, 5, 6 }
**
** In other words, each time we advance to the next sorter element, log2(N)
** key comparison operations are required, where N is the number of segments
** being merged (rounded up to the next power of 2).
*/
struct VdbeSorter {
int nWorking; /* Start a new b-tree after this many pages */
int nPage; /* Pages in file when current tree started */
int nRoot; /* Total number of segment b-trees */
int *aRoot; /* Array containing root pages */
int nAlloc; /* Allocated size of aIter[] and aTree[] */
int nTree; /* Used size of aTree/aIter (power of 2) */
VdbeSorterIter *aIter; /* Array of iterators to merge */
int *aTree; /* Current state of incremental merge */
};
/*
** The following type is a simple wrapper around a BtCursor. It caches the
** current key in variables nKey/aKey. If possible, aKey points to memory
** managed by the BtCursor object. In this case variable bFree is zero.
** Otherwise, aKey[] may point to a block of memory allocated using
** sqlite3DbMalloc(). In this case, bFree is non-zero.
*/
struct VdbeSorterIter {
BtCursor *pCsr; /* Cursor open on b-tree */
int bFree; /* True if aKey should be freed */
int nKey; /* Number of bytes in key */
u8 *aKey; /* Pointer to current key */
};
/* Minimum allowable value for the VdbeSorter.nWorking variable */
#define SORTER_MIN_SEGMENT_SIZE 10
/*
** Append integer iRoot to the VdbeSorter.aRoot[] array of the sorter object
** passed as the second argument. SQLITE_NOMEM is returned if an OOM error
** is encountered, or SQLITE_OK if no error occurs.
**
** TODO: The aRoot[] array may grow indefinitely. Fix this.
*/
static int vdbeSorterAppendRoot(sqlite3 *db, VdbeSorter *p, int iRoot){
int *aNew; /* New VdbeSorter.aRoot[] array */
aNew = sqlite3DbRealloc(db, p->aRoot, (p->nRoot+1)*sizeof(int));
if( !aNew ) return SQLITE_NOMEM;
aNew[p->nRoot] = iRoot;
p->nRoot++;
p->aRoot = aNew;
return SQLITE_OK;
}
/*
** Close any cursor and free all memory belonging to the VdbeSorterIter
** object passed as the second argument. All structure fields are set
** to zero before returning.
*/
static void vdbeSorterIterZero(sqlite3 *db, VdbeSorterIter *pIter){
if( pIter->bFree ){
sqlite3DbFree(db, pIter->aKey);
}
if( pIter->pCsr ){
sqlite3BtreeCloseCursor(pIter->pCsr);
sqlite3DbFree(db, pIter->pCsr);
}
memset(pIter, 0, sizeof(VdbeSorterIter));
}
/*
** Fetch the current key pointed to by the b-tree cursor managed by pIter
** into variables VdbeSorterIter.aKey and VdbeSorterIter.nKey. Return
** SQLITE_OK if no error occurs, or an SQLite error code otherwise.
*/
static int vdbeSorterIterLoadkey(sqlite3 *db, VdbeSorterIter *pIter){
int rc = SQLITE_OK;
assert( pIter->pCsr );
if( sqlite3BtreeEof(pIter->pCsr) ){
vdbeSorterIterZero(db, pIter);
}else{
i64 nByte64;
sqlite3BtreeKeySize(pIter->pCsr, &nByte64);
if( pIter->bFree ){
sqlite3DbFree(db, pIter->aKey);
pIter->aKey = 0;
}
pIter->nKey = nByte64;
pIter->aKey = sqlite3DbMallocRaw(db, pIter->nKey);
pIter->bFree = 1;
if( pIter->aKey==0 ){
rc = SQLITE_NOMEM;
}else{
rc = sqlite3BtreeKey(pIter->pCsr, 0, pIter->nKey, pIter->aKey);
}
}
return rc;
}
/*
** Initialize iterator pIter to scan through the b-tree with root page
** iRoot. This function leaves the iterator pointing to the first key
** in the b-tree (or EOF if the b-tree is empty).
*/
static int vdbeSorterIterInit(
sqlite3 *db, /* Database handle */
VdbeCursor *pCsr, /* Vdbe cursor handle */
int iRoot, /* Root page of b-tree to iterate */
VdbeSorterIter *pIter /* Pointer to iterator to initialize */
){
VdbeSorter *pSorter = pCsr->pSorter;
int rc;
pIter->pCsr = (BtCursor *)sqlite3DbMallocZero(db, sqlite3BtreeCursorSize());
if( !pIter->pCsr ){
rc = SQLITE_NOMEM;
}else{
rc = sqlite3BtreeCursor(pCsr->pBt, iRoot, 1, pCsr->pKeyInfo, pIter->pCsr);
}
if( rc==SQLITE_OK ){
int bDummy;
rc = sqlite3BtreeFirst(pIter->pCsr, &bDummy);
}
if( rc==SQLITE_OK ){
rc = vdbeSorterIterLoadkey(db, pIter);
}
return rc;
}
/*
** Advance iterator pIter to the next key in its b-tree.
*/
static int vdbeSorterIterNext(
sqlite3 *db,
VdbeCursor *pCsr,
VdbeSorterIter *pIter
){
int rc;
int bDummy;
VdbeSorter *pSorter = pCsr->pSorter;
rc = sqlite3BtreeNext(pIter->pCsr, &bDummy);
if( rc==SQLITE_OK ){
rc = vdbeSorterIterLoadkey(db, pIter);
}
return rc;
}
/*
** This function is called to compare two iterator keys when merging
** multiple b-tree segments. Parameter iOut is the index of the aTree[]
** value to recalculate.
*/
static int vdbeSorterDoCompare(VdbeCursor *pCsr, int iOut){
VdbeSorter *pSorter = pCsr->pSorter;
int i1;
int i2;
int iRes;
VdbeSorterIter *p1;
VdbeSorterIter *p2;
assert( iOut<pSorter->nTree && iOut>0 );
if( iOut>=(pSorter->nTree/2) ){
i1 = (iOut - pSorter->nTree/2) * 2;
i2 = i1 + 1;
}else{
i1 = pSorter->aTree[iOut*2];
i2 = pSorter->aTree[iOut*2+1];
}
p1 = &pSorter->aIter[i1];
p2 = &pSorter->aIter[i2];
if( p1->pCsr==0 ){
iRes = i2;
}else if( p2->pCsr==0 ){
iRes = i1;
}else{
char aSpace[150];
UnpackedRecord *r1;
r1 = sqlite3VdbeRecordUnpack(
pCsr->pKeyInfo, p1->nKey, p1->aKey, aSpace, sizeof(aSpace)
);
if( r1==0 ) return SQLITE_NOMEM;
if( sqlite3VdbeRecordCompare(p2->nKey, p2->aKey, r1)>=0 ){
iRes = i1;
}else{
iRes = i2;
}
sqlite3VdbeDeleteUnpackedRecord(r1);
}
pSorter->aTree[iOut] = iRes;
return SQLITE_OK;
}
/*
** Initialize the temporary index cursor just opened as a sorter cursor.
*/
int sqlite3VdbeSorterInit(sqlite3 *db, VdbeCursor *pCsr){
int rc; /* Return code */
VdbeSorter *pSorter; /* Allocated sorter object */
/* Cursor must be a temp cursor and not open on an intkey table */
assert( pCsr->pKeyInfo && pCsr->pBt );
pSorter = sqlite3DbMallocZero(db, sizeof(VdbeSorter));
if( !pSorter ) return SQLITE_NOMEM;
pCsr->pSorter = pSorter;
rc = vdbeSorterAppendRoot(db, pSorter, 2);
if( rc!=SQLITE_OK ){
sqlite3VdbeSorterClose(db, pCsr);
}
return rc;
}
/*
** Free any cursor components allocated by sqlite3VdbeSorterXXX routines.
*/
void sqlite3VdbeSorterClose(sqlite3 *db, VdbeCursor *pCsr){
VdbeSorter *pSorter = pCsr->pSorter;
if( pSorter ){
sqlite3DbFree(db, pSorter->aRoot);
if( pSorter->aIter ){
int i;
for(i=0; i<pSorter->nRoot; i++){
vdbeSorterIterZero(db, &pSorter->aIter[i]);
}
sqlite3DbFree(db, pSorter->aIter);
sqlite3DbFree(db, pSorter->aTree);
}
sqlite3DbFree(db, pSorter);
pCsr->pSorter = 0;
}
}
/*
** This function is called on a sorter cursor before each row is inserted.
** If the current b-tree being constructed is already considered "full",
** a new tree is started.
*/
int sqlite3VdbeSorterWrite(sqlite3 *db, VdbeCursor *pCsr){
int rc = SQLITE_OK; /* Return code */
VdbeSorter *pSorter = pCsr->pSorter;
if( pSorter ){
Pager *pPager = sqlite3BtreePager(pCsr->pBt);
int nPage; /* Current size of temporary file in pages */
sqlite3PagerPagecount(pPager, &nPage);
/* If pSorter->nWorking is still zero, but the temporary file has been
** created in the file-system, then the most recent insert into the
** current b-tree segment probably caused the cache to overflow (it is
** also possible that sqlite3_release_memory() was called). So set the
** size of the working set to a little less than the current size of the
** file in pages. */
if( pSorter->nWorking==0 && sqlite3PagerFile(pPager)->pMethods ){
pSorter->nWorking = nPage-5;
if( pSorter->nWorking<SORTER_MIN_SEGMENT_SIZE ){
pSorter->nWorking = SORTER_MIN_SEGMENT_SIZE;
}
}
/* If the number of pages used by the current b-tree segment is greater
** than the size of the working set (VdbeSorter.nWorking), start a new
** segment b-tree. */
if( pSorter->nWorking && nPage>=(pSorter->nPage + pSorter->nWorking) ){
BtCursor *p = pCsr->pCursor;/* Cursor structure to close and reopen */
int iRoot; /* Root page of new tree */
sqlite3BtreeCloseCursor(p);
rc = sqlite3BtreeCreateTable(pCsr->pBt, &iRoot, BTREE_BLOBKEY);
if( rc==SQLITE_OK ){
rc = vdbeSorterAppendRoot(db, pSorter, iRoot);
}
if( rc==SQLITE_OK ){
rc = sqlite3BtreeCursor(pCsr->pBt, iRoot, 1, pCsr->pKeyInfo, p);
}
pSorter->nPage = nPage;
}
}
return rc;
}
/*
** Extend the pSorter->aIter[] and pSorter->aTree[] arrays using DbRealloc().
** Return SQLITE_OK if successful, or SQLITE_NOMEM otherwise.
*/
static int vdbeSorterGrowArrays(sqlite3* db, VdbeSorter *pSorter){
int *aTree; /* New aTree[] allocation */
VdbeSorterIter *aIter; /* New aIter[] allocation */
int nOld = pSorter->nAlloc; /* Current size of arrays */
int nNew = (nOld?nOld*2:64); /* Size of arrays after reallocation */
/* Realloc aTree[]. */
aTree = sqlite3DbRealloc(db, pSorter->aTree, sizeof(int)*nNew);
if( !aTree ) return SQLITE_NOMEM;
memset(&aTree[nOld], 0, (nNew-nOld) * sizeof(int));
pSorter->aTree = aTree;
/* Realloc aIter[]. */
aIter = sqlite3DbRealloc(db, pSorter->aIter, sizeof(VdbeSorterIter)*nNew);
if( !aIter ) return SQLITE_NOMEM;
memset(&aIter[nOld], 0, (nNew-nOld) * sizeof(VdbeSorterIter));
pSorter->aIter = aIter;
/* Set VdbeSorter.nAlloc to the new size of the arrays and return OK. */
pSorter->nAlloc = nNew;
return SQLITE_OK;
}
/*
** Helper function for sqlite3VdbeSorterRewind().
*/
static int vdbeSorterInitMerge(
sqlite3 *db,
VdbeCursor *pCsr,
int iFirst,
int *piNext
){
Pager *pPager = sqlite3BtreePager(pCsr->pBt);
VdbeSorter *pSorter = pCsr->pSorter;
int rc = SQLITE_OK;
int i;
int nMaxRef = (pSorter->nWorking * 9/10);
int N = 2;
/* Initialize as many iterators as possible. */
for(i=iFirst; rc==SQLITE_OK && i<pSorter->nRoot; i++){
int iIter = i - iFirst;
assert( iIter<=pSorter->nAlloc );
if( iIter==pSorter->nAlloc ){
rc = vdbeSorterGrowArrays(db, pSorter);
}
if( rc==SQLITE_OK ){
VdbeSorterIter *pIter = &pSorter->aIter[iIter];
rc = vdbeSorterIterInit(db, pCsr, pSorter->aRoot[i], pIter);
if( i>iFirst+1 ){
int nRef = sqlite3PagerRefcount(pPager) + (i+1-iFirst);
if( nRef>=nMaxRef ){
i++;
break;
}
}
}
}
*piNext = i;
while( (i-iFirst)>N ) N += N;
pSorter->nTree = N;
/* Populate the aTree[] array. */
for(i=N-1; rc==SQLITE_OK && i>0; i--){
rc = vdbeSorterDoCompare(pCsr, i);
}
return rc;
}
/*
** Once the sorter has been populated, this function is called to prepare
** for iterating through its contents in sorted order.
*/
int sqlite3VdbeSorterRewind(sqlite3 *db, VdbeCursor *pCsr, int *pbEof){
int rc = SQLITE_OK; /* Return code */
int N;
int i;
VdbeSorter *pSorter = pCsr->pSorter;
BtCursor *p = pCsr->pCursor; /* Cursor structure */
assert( pSorter );
sqlite3BtreeCloseCursor(p);
while( rc==SQLITE_OK ){
int iNext = 0; /* Index of next segment to open */
int iRoot = 0; /* aRoot[] slot if merging to a new segment */
do {
rc = vdbeSorterInitMerge(db, pCsr, iNext, &iNext);
if( rc==SQLITE_OK && (iRoot>0 || iNext<pSorter->nRoot) ){
int pgno;
int bEof = 0;
rc = sqlite3BtreeCreateTable(pCsr->pBt, &pgno, BTREE_BLOBKEY);
if( rc==SQLITE_OK ){
pSorter->aRoot[iRoot] = pgno;
rc = sqlite3BtreeCursor(pCsr->pBt, pgno, 1, pCsr->pKeyInfo, p);
}
while( rc==SQLITE_OK && bEof==0 ){
VdbeSorterIter *pIter = &pSorter->aIter[ pSorter->aTree[1] ];
rc = sqlite3BtreeInsert(p, pIter->aKey, pIter->nKey, 0, 0, 0, 1, 0);
if( rc==SQLITE_OK ){
rc = sqlite3VdbeSorterNext(db, pCsr, &bEof);
}
}
sqlite3BtreeCloseCursor(p);
iRoot++;
}
} while( rc==SQLITE_OK && iNext<pSorter->nRoot );
if( iRoot==0 ) break;
pSorter->nRoot = iRoot;
}
*pbEof = (pSorter->aIter[pSorter->aTree[1]].pCsr==0);
return rc;
}
/*
** Advance to the next element in the sorter.
*/
int sqlite3VdbeSorterNext(sqlite3 *db, VdbeCursor *pCsr, int *pbEof){
VdbeSorter *pSorter = pCsr->pSorter;
int iPrev = pSorter->aTree[1]; /* Index of iterator to advance */
int i; /* Index of aTree[] to recalculate */
int rc; /* Return code */
rc = vdbeSorterIterNext(db, pCsr, &pSorter->aIter[iPrev]);
for(i=(pSorter->nTree+iPrev)/2; rc==SQLITE_OK && i>0; i=i/2){
rc = vdbeSorterDoCompare(pCsr, i);
}
*pbEof = (pSorter->aIter[pSorter->aTree[1]].pCsr==0);
return rc;
}
/*
** Copy the current sorter key into the memory cell pOut.
*/
int sqlite3VdbeSorterRowkey(sqlite3 *db, VdbeCursor *pCsr, Mem *pOut){
VdbeSorter *pSorter = pCsr->pSorter;
VdbeSorterIter *pIter;
pIter = &pSorter->aIter[ pSorter->aTree[1] ];
if( sqlite3VdbeMemGrow(pOut, pIter->nKey, 0) ){
return SQLITE_NOMEM;
}
pOut->n = pIter->nKey;
MemSetTypeFlag(pOut, MEM_Blob);
memcpy(pOut->z, pIter->aKey, pIter->nKey);
return SQLITE_OK;
}