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sqlite/src/analyze.c
drh 403869680b Sometimes it makes sense to do a full table scan rather than try to use 
an index when most of the rows will be selected.  This branch is trying to
tune the query planner to make that happen more often.

FossilOrigin-Name: 0f42099ad65855c94af8472f3a6fddac7fc2a82e8fdfcc06a298eb6683a28688
2020-10-22 15:47:48 +00:00

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/*
** 2005-07-08
**
** 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 associated with the ANALYZE command.
**
** The ANALYZE command gather statistics about the content of tables
** and indices. These statistics are made available to the query planner
** to help it make better decisions about how to perform queries.
**
** The following system tables are or have been supported:
**
** CREATE TABLE sqlite_stat1(tbl, idx, stat);
** CREATE TABLE sqlite_stat2(tbl, idx, sampleno, sample);
** CREATE TABLE sqlite_stat3(tbl, idx, nEq, nLt, nDLt, sample);
** CREATE TABLE sqlite_stat4(tbl, idx, nEq, nLt, nDLt, sample);
**
** Additional tables might be added in future releases of SQLite.
** The sqlite_stat2 table is not created or used unless the SQLite version
** is between 3.6.18 and 3.7.8, inclusive, and unless SQLite is compiled
** with SQLITE_ENABLE_STAT2. The sqlite_stat2 table is deprecated.
** The sqlite_stat2 table is superseded by sqlite_stat3, which is only
** created and used by SQLite versions 3.7.9 through 3.29.0 when
** SQLITE_ENABLE_STAT3 defined. The functionality of sqlite_stat3
** is a superset of sqlite_stat2 and is also now deprecated. The
** sqlite_stat4 is an enhanced version of sqlite_stat3 and is only
** available when compiled with SQLITE_ENABLE_STAT4 and in SQLite
** versions 3.8.1 and later. STAT4 is the only variant that is still
** supported.
**
** For most applications, sqlite_stat1 provides all the statistics required
** for the query planner to make good choices.
**
** Format of sqlite_stat1:
**
** There is normally one row per index, with the index identified by the
** name in the idx column. The tbl column is the name of the table to
** which the index belongs. In each such row, the stat column will be
** a string consisting of a list of integers. The first integer in this
** list is the number of rows in the index. (This is the same as the
** number of rows in the table, except for partial indices.) The second
** integer is the average number of rows in the index that have the same
** value in the first column of the index. The third integer is the average
** number of rows in the index that have the same value for the first two
** columns. The N-th integer (for N>1) is the average number of rows in
** the index which have the same value for the first N-1 columns. For
** a K-column index, there will be K+1 integers in the stat column. If
** the index is unique, then the last integer will be 1.
**
** The list of integers in the stat column can optionally be followed
** by the keyword "unordered". The "unordered" keyword, if it is present,
** must be separated from the last integer by a single space. If the
** "unordered" keyword is present, then the query planner assumes that
** the index is unordered and will not use the index for a range query.
**
** If the sqlite_stat1.idx column is NULL, then the sqlite_stat1.stat
** column contains a single integer which is the (estimated) number of
** rows in the table identified by sqlite_stat1.tbl.
**
** Format of sqlite_stat2:
**
** The sqlite_stat2 is only created and is only used if SQLite is compiled
** with SQLITE_ENABLE_STAT2 and if the SQLite version number is between
** 3.6.18 and 3.7.8. The "stat2" table contains additional information
** about the distribution of keys within an index. The index is identified by
** the "idx" column and the "tbl" column is the name of the table to which
** the index belongs. There are usually 10 rows in the sqlite_stat2
** table for each index.
**
** The sqlite_stat2 entries for an index that have sampleno between 0 and 9
** inclusive are samples of the left-most key value in the index taken at
** evenly spaced points along the index. Let the number of samples be S
** (10 in the standard build) and let C be the number of rows in the index.
** Then the sampled rows are given by:
**
** rownumber = (i*C*2 + C)/(S*2)
**
** For i between 0 and S-1. Conceptually, the index space is divided into
** S uniform buckets and the samples are the middle row from each bucket.
**
** The format for sqlite_stat2 is recorded here for legacy reference. This
** version of SQLite does not support sqlite_stat2. It neither reads nor
** writes the sqlite_stat2 table. This version of SQLite only supports
** sqlite_stat3.
**
** Format for sqlite_stat3:
**
** The sqlite_stat3 format is a subset of sqlite_stat4. Hence, the
** sqlite_stat4 format will be described first. Further information
** about sqlite_stat3 follows the sqlite_stat4 description.
**
** Format for sqlite_stat4:
**
** As with sqlite_stat2, the sqlite_stat4 table contains histogram data
** to aid the query planner in choosing good indices based on the values
** that indexed columns are compared against in the WHERE clauses of
** queries.
**
** The sqlite_stat4 table contains multiple entries for each index.
** The idx column names the index and the tbl column is the table of the
** index. If the idx and tbl columns are the same, then the sample is
** of the INTEGER PRIMARY KEY. The sample column is a blob which is the
** binary encoding of a key from the index. The nEq column is a
** list of integers. The first integer is the approximate number
** of entries in the index whose left-most column exactly matches
** the left-most column of the sample. The second integer in nEq
** is the approximate number of entries in the index where the
** first two columns match the first two columns of the sample.
** And so forth. nLt is another list of integers that show the approximate
** number of entries that are strictly less than the sample. The first
** integer in nLt contains the number of entries in the index where the
** left-most column is less than the left-most column of the sample.
** The K-th integer in the nLt entry is the number of index entries
** where the first K columns are less than the first K columns of the
** sample. The nDLt column is like nLt except that it contains the
** number of distinct entries in the index that are less than the
** sample.
**
** There can be an arbitrary number of sqlite_stat4 entries per index.
** The ANALYZE command will typically generate sqlite_stat4 tables
** that contain between 10 and 40 samples which are distributed across
** the key space, though not uniformly, and which include samples with
** large nEq values.
**
** Format for sqlite_stat3 redux:
**
** The sqlite_stat3 table is like sqlite_stat4 except that it only
** looks at the left-most column of the index. The sqlite_stat3.sample
** column contains the actual value of the left-most column instead
** of a blob encoding of the complete index key as is found in
** sqlite_stat4.sample. The nEq, nLt, and nDLt entries of sqlite_stat3
** all contain just a single integer which is the same as the first
** integer in the equivalent columns in sqlite_stat4.
*/
#ifndef SQLITE_OMIT_ANALYZE
#include "sqliteInt.h"
#if defined(SQLITE_ENABLE_STAT4)
# define IsStat4 1
#else
# define IsStat4 0
# undef SQLITE_STAT4_SAMPLES
# define SQLITE_STAT4_SAMPLES 1
#endif
/*
** This routine generates code that opens the sqlite_statN tables.
** The sqlite_stat1 table is always relevant. sqlite_stat2 is now
** obsolete. sqlite_stat3 and sqlite_stat4 are only opened when
** appropriate compile-time options are provided.
**
** If the sqlite_statN tables do not previously exist, it is created.
**
** Argument zWhere may be a pointer to a buffer containing a table name,
** or it may be a NULL pointer. If it is not NULL, then all entries in
** the sqlite_statN tables associated with the named table are deleted.
** If zWhere==0, then code is generated to delete all stat table entries.
*/
static void openStatTable(
Parse *pParse, /* Parsing context */
int iDb, /* The database we are looking in */
int iStatCur, /* Open the sqlite_stat1 table on this cursor */
const char *zWhere, /* Delete entries for this table or index */
const char *zWhereType /* Either "tbl" or "idx" */
){
static const struct {
const char *zName;
const char *zCols;
} aTable[] = {
{ "sqlite_stat1", "tbl,idx,stat" },
#if defined(SQLITE_ENABLE_STAT4)
{ "sqlite_stat4", "tbl,idx,neq,nlt,ndlt,sample" },
#else
{ "sqlite_stat4", 0 },
#endif
{ "sqlite_stat3", 0 },
};
int i;
sqlite3 *db = pParse->db;
Db *pDb;
Vdbe *v = sqlite3GetVdbe(pParse);
u32 aRoot[ArraySize(aTable)];
u8 aCreateTbl[ArraySize(aTable)];
#ifdef SQLITE_ENABLE_STAT4
const int nToOpen = OptimizationEnabled(db,SQLITE_Stat4) ? 2 : 1;
#else
const int nToOpen = 1;
#endif
if( v==0 ) return;
assert( sqlite3BtreeHoldsAllMutexes(db) );
assert( sqlite3VdbeDb(v)==db );
pDb = &db->aDb[iDb];
/* Create new statistic tables if they do not exist, or clear them
** if they do already exist.
*/
for(i=0; i<ArraySize(aTable); i++){
const char *zTab = aTable[i].zName;
Table *pStat;
aCreateTbl[i] = 0;
if( (pStat = sqlite3FindTable(db, zTab, pDb->zDbSName))==0 ){
if( i<nToOpen ){
/* The sqlite_statN table does not exist. Create it. Note that a
** side-effect of the CREATE TABLE statement is to leave the rootpage
** of the new table in register pParse->regRoot. This is important
** because the OpenWrite opcode below will be needing it. */
sqlite3NestedParse(pParse,
"CREATE TABLE %Q.%s(%s)", pDb->zDbSName, zTab, aTable[i].zCols
);
aRoot[i] = (u32)pParse->regRoot;
aCreateTbl[i] = OPFLAG_P2ISREG;
}
}else{
/* The table already exists. If zWhere is not NULL, delete all entries
** associated with the table zWhere. If zWhere is NULL, delete the
** entire contents of the table. */
aRoot[i] = pStat->tnum;
sqlite3TableLock(pParse, iDb, aRoot[i], 1, zTab);
if( zWhere ){
sqlite3NestedParse(pParse,
"DELETE FROM %Q.%s WHERE %s=%Q",
pDb->zDbSName, zTab, zWhereType, zWhere
);
#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
}else if( db->xPreUpdateCallback ){
sqlite3NestedParse(pParse, "DELETE FROM %Q.%s", pDb->zDbSName, zTab);
#endif
}else{
/* The sqlite_stat[134] table already exists. Delete all rows. */
sqlite3VdbeAddOp2(v, OP_Clear, (int)aRoot[i], iDb);
}
}
}
/* Open the sqlite_stat[134] tables for writing. */
for(i=0; i<nToOpen; i++){
assert( i<ArraySize(aTable) );
sqlite3VdbeAddOp4Int(v, OP_OpenWrite, iStatCur+i, (int)aRoot[i], iDb, 3);
sqlite3VdbeChangeP5(v, aCreateTbl[i]);
VdbeComment((v, aTable[i].zName));
}
}
/*
** Recommended number of samples for sqlite_stat4
*/
#ifndef SQLITE_STAT4_SAMPLES
# define SQLITE_STAT4_SAMPLES 24
#endif
/*
** Three SQL functions - stat_init(), stat_push(), and stat_get() -
** share an instance of the following structure to hold their state
** information.
*/
typedef struct StatAccum StatAccum;
typedef struct StatSample StatSample;
struct StatSample {
tRowcnt *anEq; /* sqlite_stat4.nEq */
tRowcnt *anDLt; /* sqlite_stat4.nDLt */
#ifdef SQLITE_ENABLE_STAT4
tRowcnt *anLt; /* sqlite_stat4.nLt */
union {
i64 iRowid; /* Rowid in main table of the key */
u8 *aRowid; /* Key for WITHOUT ROWID tables */
} u;
u32 nRowid; /* Sizeof aRowid[] */
u8 isPSample; /* True if a periodic sample */
int iCol; /* If !isPSample, the reason for inclusion */
u32 iHash; /* Tiebreaker hash */
#endif
};
struct StatAccum {
sqlite3 *db; /* Database connection, for malloc() */
tRowcnt nEst; /* Estimated number of rows */
tRowcnt nRow; /* Number of rows visited so far */
int nLimit; /* Analysis row-scan limit */
int nCol; /* Number of columns in index + pk/rowid */
int nKeyCol; /* Number of index columns w/o the pk/rowid */
u8 nSkipAhead; /* Number of times of skip-ahead */
StatSample current; /* Current row as a StatSample */
#ifdef SQLITE_ENABLE_STAT4
tRowcnt nPSample; /* How often to do a periodic sample */
int mxSample; /* Maximum number of samples to accumulate */
u32 iPrn; /* Pseudo-random number used for sampling */
StatSample *aBest; /* Array of nCol best samples */
int iMin; /* Index in a[] of entry with minimum score */
int nSample; /* Current number of samples */
int nMaxEqZero; /* Max leading 0 in anEq[] for any a[] entry */
int iGet; /* Index of current sample accessed by stat_get() */
StatSample *a; /* Array of mxSample StatSample objects */
#endif
};
/* Reclaim memory used by a StatSample
*/
#ifdef SQLITE_ENABLE_STAT4
static void sampleClear(sqlite3 *db, StatSample *p){
assert( db!=0 );
if( p->nRowid ){
sqlite3DbFree(db, p->u.aRowid);
p->nRowid = 0;
}
}
#endif
/* Initialize the BLOB value of a ROWID
*/
#ifdef SQLITE_ENABLE_STAT4
static void sampleSetRowid(sqlite3 *db, StatSample *p, int n, const u8 *pData){
assert( db!=0 );
if( p->nRowid ) sqlite3DbFree(db, p->u.aRowid);
p->u.aRowid = sqlite3DbMallocRawNN(db, n);
if( p->u.aRowid ){
p->nRowid = n;
memcpy(p->u.aRowid, pData, n);
}else{
p->nRowid = 0;
}
}
#endif
/* Initialize the INTEGER value of a ROWID.
*/
#ifdef SQLITE_ENABLE_STAT4
static void sampleSetRowidInt64(sqlite3 *db, StatSample *p, i64 iRowid){
assert( db!=0 );
if( p->nRowid ) sqlite3DbFree(db, p->u.aRowid);
p->nRowid = 0;
p->u.iRowid = iRowid;
}
#endif
/*
** Copy the contents of object (*pFrom) into (*pTo).
*/
#ifdef SQLITE_ENABLE_STAT4
static void sampleCopy(StatAccum *p, StatSample *pTo, StatSample *pFrom){
pTo->isPSample = pFrom->isPSample;
pTo->iCol = pFrom->iCol;
pTo->iHash = pFrom->iHash;
memcpy(pTo->anEq, pFrom->anEq, sizeof(tRowcnt)*p->nCol);
memcpy(pTo->anLt, pFrom->anLt, sizeof(tRowcnt)*p->nCol);
memcpy(pTo->anDLt, pFrom->anDLt, sizeof(tRowcnt)*p->nCol);
if( pFrom->nRowid ){
sampleSetRowid(p->db, pTo, pFrom->nRowid, pFrom->u.aRowid);
}else{
sampleSetRowidInt64(p->db, pTo, pFrom->u.iRowid);
}
}
#endif
/*
** Reclaim all memory of a StatAccum structure.
*/
static void statAccumDestructor(void *pOld){
StatAccum *p = (StatAccum*)pOld;
#ifdef SQLITE_ENABLE_STAT4
if( p->mxSample ){
int i;
for(i=0; i<p->nCol; i++) sampleClear(p->db, p->aBest+i);
for(i=0; i<p->mxSample; i++) sampleClear(p->db, p->a+i);
sampleClear(p->db, &p->current);
}
#endif
sqlite3DbFree(p->db, p);
}
/*
** Implementation of the stat_init(N,K,C,L) SQL function. The four parameters
** are:
** N: The number of columns in the index including the rowid/pk (note 1)
** K: The number of columns in the index excluding the rowid/pk.
** C: Estimated number of rows in the index
** L: A limit on the number of rows to scan, or 0 for no-limit
**
** Note 1: In the special case of the covering index that implements a
** WITHOUT ROWID table, N is the number of PRIMARY KEY columns, not the
** total number of columns in the table.
**
** For indexes on ordinary rowid tables, N==K+1. But for indexes on
** WITHOUT ROWID tables, N=K+P where P is the number of columns in the
** PRIMARY KEY of the table. The covering index that implements the
** original WITHOUT ROWID table as N==K as a special case.
**
** This routine allocates the StatAccum object in heap memory. The return
** value is a pointer to the StatAccum object. The datatype of the
** return value is BLOB, but it is really just a pointer to the StatAccum
** object.
*/
static void statInit(
sqlite3_context *context,
int argc,
sqlite3_value **argv
){
StatAccum *p;
int nCol; /* Number of columns in index being sampled */
int nKeyCol; /* Number of key columns */
int nColUp; /* nCol rounded up for alignment */
int n; /* Bytes of space to allocate */
sqlite3 *db = sqlite3_context_db_handle(context); /* Database connection */
#ifdef SQLITE_ENABLE_STAT4
/* Maximum number of samples. 0 if STAT4 data is not collected */
int mxSample = OptimizationEnabled(db,SQLITE_Stat4) ?SQLITE_STAT4_SAMPLES :0;
#endif
/* Decode the three function arguments */
UNUSED_PARAMETER(argc);
nCol = sqlite3_value_int(argv[0]);
assert( nCol>0 );
nColUp = sizeof(tRowcnt)<8 ? (nCol+1)&~1 : nCol;
nKeyCol = sqlite3_value_int(argv[1]);
assert( nKeyCol<=nCol );
assert( nKeyCol>0 );
/* Allocate the space required for the StatAccum object */
n = sizeof(*p)
+ sizeof(tRowcnt)*nColUp /* StatAccum.anEq */
+ sizeof(tRowcnt)*nColUp; /* StatAccum.anDLt */
#ifdef SQLITE_ENABLE_STAT4
if( mxSample ){
n += sizeof(tRowcnt)*nColUp /* StatAccum.anLt */
+ sizeof(StatSample)*(nCol+mxSample) /* StatAccum.aBest[], a[] */
+ sizeof(tRowcnt)*3*nColUp*(nCol+mxSample);
}
#endif
db = sqlite3_context_db_handle(context);
p = sqlite3DbMallocZero(db, n);
if( p==0 ){
sqlite3_result_error_nomem(context);
return;
}
p->db = db;
p->nEst = sqlite3_value_int64(argv[2]);
p->nRow = 0;
p->nLimit = sqlite3_value_int64(argv[3]);
p->nCol = nCol;
p->nKeyCol = nKeyCol;
p->nSkipAhead = 0;
p->current.anDLt = (tRowcnt*)&p[1];
p->current.anEq = &p->current.anDLt[nColUp];
#ifdef SQLITE_ENABLE_STAT4
p->mxSample = p->nLimit==0 ? mxSample : 0;
if( mxSample ){
u8 *pSpace; /* Allocated space not yet assigned */
int i; /* Used to iterate through p->aSample[] */
p->iGet = -1;
p->nPSample = (tRowcnt)(p->nEst/(mxSample/3+1) + 1);
p->current.anLt = &p->current.anEq[nColUp];
p->iPrn = 0x689e962d*(u32)nCol ^ 0xd0944565*(u32)sqlite3_value_int(argv[2]);
/* Set up the StatAccum.a[] and aBest[] arrays */
p->a = (struct StatSample*)&p->current.anLt[nColUp];
p->aBest = &p->a[mxSample];
pSpace = (u8*)(&p->a[mxSample+nCol]);
for(i=0; i<(mxSample+nCol); i++){
p->a[i].anEq = (tRowcnt *)pSpace; pSpace += (sizeof(tRowcnt) * nColUp);
p->a[i].anLt = (tRowcnt *)pSpace; pSpace += (sizeof(tRowcnt) * nColUp);
p->a[i].anDLt = (tRowcnt *)pSpace; pSpace += (sizeof(tRowcnt) * nColUp);
}
assert( (pSpace - (u8*)p)==n );
for(i=0; i<nCol; i++){
p->aBest[i].iCol = i;
}
}
#endif
/* Return a pointer to the allocated object to the caller. Note that
** only the pointer (the 2nd parameter) matters. The size of the object
** (given by the 3rd parameter) is never used and can be any positive
** value. */
sqlite3_result_blob(context, p, sizeof(*p), statAccumDestructor);
}
static const FuncDef statInitFuncdef = {
4, /* nArg */
SQLITE_UTF8, /* funcFlags */
0, /* pUserData */
0, /* pNext */
statInit, /* xSFunc */
0, /* xFinalize */
0, 0, /* xValue, xInverse */
"stat_init", /* zName */
{0}
};
#ifdef SQLITE_ENABLE_STAT4
/*
** pNew and pOld are both candidate non-periodic samples selected for
** the same column (pNew->iCol==pOld->iCol). Ignoring this column and
** considering only any trailing columns and the sample hash value, this
** function returns true if sample pNew is to be preferred over pOld.
** In other words, if we assume that the cardinalities of the selected
** column for pNew and pOld are equal, is pNew to be preferred over pOld.
**
** This function assumes that for each argument sample, the contents of
** the anEq[] array from pSample->anEq[pSample->iCol+1] onwards are valid.
*/
static int sampleIsBetterPost(
StatAccum *pAccum,
StatSample *pNew,
StatSample *pOld
){
int nCol = pAccum->nCol;
int i;
assert( pNew->iCol==pOld->iCol );
for(i=pNew->iCol+1; i<nCol; i++){
if( pNew->anEq[i]>pOld->anEq[i] ) return 1;
if( pNew->anEq[i]<pOld->anEq[i] ) return 0;
}
if( pNew->iHash>pOld->iHash ) return 1;
return 0;
}
#endif
#ifdef SQLITE_ENABLE_STAT4
/*
** Return true if pNew is to be preferred over pOld.
**
** This function assumes that for each argument sample, the contents of
** the anEq[] array from pSample->anEq[pSample->iCol] onwards are valid.
*/
static int sampleIsBetter(
StatAccum *pAccum,
StatSample *pNew,
StatSample *pOld
){
tRowcnt nEqNew = pNew->anEq[pNew->iCol];
tRowcnt nEqOld = pOld->anEq[pOld->iCol];
assert( pOld->isPSample==0 && pNew->isPSample==0 );
assert( IsStat4 || (pNew->iCol==0 && pOld->iCol==0) );
if( (nEqNew>nEqOld) ) return 1;
if( nEqNew==nEqOld ){
if( pNew->iCol<pOld->iCol ) return 1;
return (pNew->iCol==pOld->iCol && sampleIsBetterPost(pAccum, pNew, pOld));
}
return 0;
}
/*
** Copy the contents of sample *pNew into the p->a[] array. If necessary,
** remove the least desirable sample from p->a[] to make room.
*/
static void sampleInsert(StatAccum *p, StatSample *pNew, int nEqZero){
StatSample *pSample = 0;
int i;
assert( IsStat4 || nEqZero==0 );
/* StatAccum.nMaxEqZero is set to the maximum number of leading 0
** values in the anEq[] array of any sample in StatAccum.a[]. In
** other words, if nMaxEqZero is n, then it is guaranteed that there
** are no samples with StatSample.anEq[m]==0 for (m>=n). */
if( nEqZero>p->nMaxEqZero ){
p->nMaxEqZero = nEqZero;
}
if( pNew->isPSample==0 ){
StatSample *pUpgrade = 0;
assert( pNew->anEq[pNew->iCol]>0 );
/* This sample is being added because the prefix that ends in column
** iCol occurs many times in the table. However, if we have already
** added a sample that shares this prefix, there is no need to add
** this one. Instead, upgrade the priority of the highest priority
** existing sample that shares this prefix. */
for(i=p->nSample-1; i>=0; i--){
StatSample *pOld = &p->a[i];
if( pOld->anEq[pNew->iCol]==0 ){
if( pOld->isPSample ) return;
assert( pOld->iCol>pNew->iCol );
assert( sampleIsBetter(p, pNew, pOld) );
if( pUpgrade==0 || sampleIsBetter(p, pOld, pUpgrade) ){
pUpgrade = pOld;
}
}
}
if( pUpgrade ){
pUpgrade->iCol = pNew->iCol;
pUpgrade->anEq[pUpgrade->iCol] = pNew->anEq[pUpgrade->iCol];
goto find_new_min;
}
}
/* If necessary, remove sample iMin to make room for the new sample. */
if( p->nSample>=p->mxSample ){
StatSample *pMin = &p->a[p->iMin];
tRowcnt *anEq = pMin->anEq;
tRowcnt *anLt = pMin->anLt;
tRowcnt *anDLt = pMin->anDLt;
sampleClear(p->db, pMin);
memmove(pMin, &pMin[1], sizeof(p->a[0])*(p->nSample-p->iMin-1));
pSample = &p->a[p->nSample-1];
pSample->nRowid = 0;
pSample->anEq = anEq;
pSample->anDLt = anDLt;
pSample->anLt = anLt;
p->nSample = p->mxSample-1;
}
/* The "rows less-than" for the rowid column must be greater than that
** for the last sample in the p->a[] array. Otherwise, the samples would
** be out of order. */
assert( p->nSample==0
|| pNew->anLt[p->nCol-1] > p->a[p->nSample-1].anLt[p->nCol-1] );
/* Insert the new sample */
pSample = &p->a[p->nSample];
sampleCopy(p, pSample, pNew);
p->nSample++;
/* Zero the first nEqZero entries in the anEq[] array. */
memset(pSample->anEq, 0, sizeof(tRowcnt)*nEqZero);
find_new_min:
if( p->nSample>=p->mxSample ){
int iMin = -1;
for(i=0; i<p->mxSample; i++){
if( p->a[i].isPSample ) continue;
if( iMin<0 || sampleIsBetter(p, &p->a[iMin], &p->a[i]) ){
iMin = i;
}
}
assert( iMin>=0 );
p->iMin = iMin;
}
}
#endif /* SQLITE_ENABLE_STAT4 */
#ifdef SQLITE_ENABLE_STAT4
/*
** Field iChng of the index being scanned has changed. So at this point
** p->current contains a sample that reflects the previous row of the
** index. The value of anEq[iChng] and subsequent anEq[] elements are
** correct at this point.
*/
static void samplePushPrevious(StatAccum *p, int iChng){
int i;
/* Check if any samples from the aBest[] array should be pushed
** into IndexSample.a[] at this point. */
for(i=(p->nCol-2); i>=iChng; i--){
StatSample *pBest = &p->aBest[i];
pBest->anEq[i] = p->current.anEq[i];
if( p->nSample<p->mxSample || sampleIsBetter(p, pBest, &p->a[p->iMin]) ){
sampleInsert(p, pBest, i);
}
}
/* Check that no sample contains an anEq[] entry with an index of
** p->nMaxEqZero or greater set to zero. */
for(i=p->nSample-1; i>=0; i--){
int j;
for(j=p->nMaxEqZero; j<p->nCol; j++) assert( p->a[i].anEq[j]>0 );
}
/* Update the anEq[] fields of any samples already collected. */
if( iChng<p->nMaxEqZero ){
for(i=p->nSample-1; i>=0; i--){
int j;
for(j=iChng; j<p->nCol; j++){
if( p->a[i].anEq[j]==0 ) p->a[i].anEq[j] = p->current.anEq[j];
}
}
p->nMaxEqZero = iChng;
}
}
#endif /* SQLITE_ENABLE_STAT4 */
/*
** Implementation of the stat_push SQL function: stat_push(P,C,R)
** Arguments:
**
** P Pointer to the StatAccum object created by stat_init()
** C Index of left-most column to differ from previous row
** R Rowid for the current row. Might be a key record for
** WITHOUT ROWID tables.
**
** The purpose of this routine is to collect statistical data and/or
** samples from the index being analyzed into the StatAccum object.
** The stat_get() SQL function will be used afterwards to
** retrieve the information gathered.
**
** This SQL function usually returns NULL, but might return an integer
** if it wants the byte-code to do special processing.
**
** The R parameter is only used for STAT4
*/
static void statPush(
sqlite3_context *context,
int argc,
sqlite3_value **argv
){
int i;
/* The three function arguments */
StatAccum *p = (StatAccum*)sqlite3_value_blob(argv[0]);
int iChng = sqlite3_value_int(argv[1]);
UNUSED_PARAMETER( argc );
UNUSED_PARAMETER( context );
assert( p->nCol>0 );
assert( iChng<p->nCol );
if( p->nRow==0 ){
/* This is the first call to this function. Do initialization. */
for(i=0; i<p->nCol; i++) p->current.anEq[i] = 1;
}else{
/* Second and subsequent calls get processed here */
#ifdef SQLITE_ENABLE_STAT4
if( p->mxSample ) samplePushPrevious(p, iChng);
#endif
/* Update anDLt[], anLt[] and anEq[] to reflect the values that apply
** to the current row of the index. */
for(i=0; i<iChng; i++){
p->current.anEq[i]++;
}
for(i=iChng; i<p->nCol; i++){
p->current.anDLt[i]++;
#ifdef SQLITE_ENABLE_STAT4
if( p->mxSample ) p->current.anLt[i] += p->current.anEq[i];
#endif
p->current.anEq[i] = 1;
}
}
p->nRow++;
#ifdef SQLITE_ENABLE_STAT4
if( p->mxSample ){
tRowcnt nLt;
if( sqlite3_value_type(argv[2])==SQLITE_INTEGER ){
sampleSetRowidInt64(p->db, &p->current, sqlite3_value_int64(argv[2]));
}else{
sampleSetRowid(p->db, &p->current, sqlite3_value_bytes(argv[2]),
sqlite3_value_blob(argv[2]));
}
p->current.iHash = p->iPrn = p->iPrn*1103515245 + 12345;
nLt = p->current.anLt[p->nCol-1];
/* Check if this is to be a periodic sample. If so, add it. */
if( (nLt/p->nPSample)!=(nLt+1)/p->nPSample ){
p->current.isPSample = 1;
p->current.iCol = 0;
sampleInsert(p, &p->current, p->nCol-1);
p->current.isPSample = 0;
}
/* Update the aBest[] array. */
for(i=0; i<(p->nCol-1); i++){
p->current.iCol = i;
if( i>=iChng || sampleIsBetterPost(p, &p->current, &p->aBest[i]) ){
sampleCopy(p, &p->aBest[i], &p->current);
}
}
}else
#endif
if( p->nLimit && p->nRow>(tRowcnt)p->nLimit*(p->nSkipAhead+1) ){
p->nSkipAhead++;
sqlite3_result_int(context, p->current.anDLt[0]>0);
}
}
static const FuncDef statPushFuncdef = {
2+IsStat4, /* nArg */
SQLITE_UTF8, /* funcFlags */
0, /* pUserData */
0, /* pNext */
statPush, /* xSFunc */
0, /* xFinalize */
0, 0, /* xValue, xInverse */
"stat_push", /* zName */
{0}
};
#define STAT_GET_STAT1 0 /* "stat" column of stat1 table */
#define STAT_GET_ROWID 1 /* "rowid" column of stat[34] entry */
#define STAT_GET_NEQ 2 /* "neq" column of stat[34] entry */
#define STAT_GET_NLT 3 /* "nlt" column of stat[34] entry */
#define STAT_GET_NDLT 4 /* "ndlt" column of stat[34] entry */
/*
** Implementation of the stat_get(P,J) SQL function. This routine is
** used to query statistical information that has been gathered into
** the StatAccum object by prior calls to stat_push(). The P parameter
** has type BLOB but it is really just a pointer to the StatAccum object.
** The content to returned is determined by the parameter J
** which is one of the STAT_GET_xxxx values defined above.
**
** The stat_get(P,J) function is not available to generic SQL. It is
** inserted as part of a manually constructed bytecode program. (See
** the callStatGet() routine below.) It is guaranteed that the P
** parameter will always be a pointer to a StatAccum object, never a
** NULL.
**
** If STAT4 is not enabled, then J is always
** STAT_GET_STAT1 and is hence omitted and this routine becomes
** a one-parameter function, stat_get(P), that always returns the
** stat1 table entry information.
*/
static void statGet(
sqlite3_context *context,
int argc,
sqlite3_value **argv
){
StatAccum *p = (StatAccum*)sqlite3_value_blob(argv[0]);
#ifdef SQLITE_ENABLE_STAT4
/* STAT4 has a parameter on this routine. */
int eCall = sqlite3_value_int(argv[1]);
assert( argc==2 );
assert( eCall==STAT_GET_STAT1 || eCall==STAT_GET_NEQ
|| eCall==STAT_GET_ROWID || eCall==STAT_GET_NLT
|| eCall==STAT_GET_NDLT
);
assert( eCall==STAT_GET_STAT1 || p->mxSample );
if( eCall==STAT_GET_STAT1 )
#else
assert( argc==1 );
#endif
{
/* Return the value to store in the "stat" column of the sqlite_stat1
** table for this index.
**
** The value is a string composed of a list of integers describing
** the index. The first integer in the list is the total number of
** entries in the index. There is one additional integer in the list
** for each indexed column. This additional integer is an estimate of
** the number of rows matched by a equality query on the index using
** a key with the corresponding number of fields. In other words,
** if the index is on columns (a,b) and the sqlite_stat1 value is
** "100 10 2", then SQLite estimates that:
**
** * the index contains 100 rows,
** * "WHERE a=?" matches 10 rows, and
** * "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:
**
** I = (K+D-1)/D
*/
char *z;
int i;
char *zRet = sqlite3MallocZero( (p->nKeyCol+1)*25 );
if( zRet==0 ){
sqlite3_result_error_nomem(context);
return;
}
sqlite3_snprintf(24, zRet, "%llu",
p->nSkipAhead ? (u64)p->nEst : (u64)p->nRow);
z = zRet + sqlite3Strlen30(zRet);
for(i=0; i<p->nKeyCol; i++){
u64 nDistinct = p->current.anDLt[i] + 1;
u64 iVal = (p->nRow + nDistinct - 1) / nDistinct;
sqlite3_snprintf(24, z, " %llu", iVal);
z += sqlite3Strlen30(z);
assert( p->current.anEq[i] );
}
assert( z[0]=='\0' && z>zRet );
sqlite3_result_text(context, zRet, -1, sqlite3_free);
}
#ifdef SQLITE_ENABLE_STAT4
else if( eCall==STAT_GET_ROWID ){
if( p->iGet<0 ){
samplePushPrevious(p, 0);
p->iGet = 0;
}
if( p->iGet<p->nSample ){
StatSample *pS = p->a + p->iGet;
if( pS->nRowid==0 ){
sqlite3_result_int64(context, pS->u.iRowid);
}else{
sqlite3_result_blob(context, pS->u.aRowid, pS->nRowid,
SQLITE_TRANSIENT);
}
}
}else{
tRowcnt *aCnt = 0;
assert( p->iGet<p->nSample );
switch( eCall ){
case STAT_GET_NEQ: aCnt = p->a[p->iGet].anEq; break;
case STAT_GET_NLT: aCnt = p->a[p->iGet].anLt; break;
default: {
aCnt = p->a[p->iGet].anDLt;
p->iGet++;
break;
}
}
{
char *zRet = sqlite3MallocZero(p->nCol * 25);
if( zRet==0 ){
sqlite3_result_error_nomem(context);
}else{
int i;
char *z = zRet;
for(i=0; i<p->nCol; i++){
sqlite3_snprintf(24, z, "%llu ", (u64)aCnt[i]);
z += sqlite3Strlen30(z);
}
assert( z[0]=='\0' && z>zRet );
z[-1] = '\0';
sqlite3_result_text(context, zRet, -1, sqlite3_free);
}
}
}
#endif /* SQLITE_ENABLE_STAT4 */
#ifndef SQLITE_DEBUG
UNUSED_PARAMETER( argc );
#endif
}
static const FuncDef statGetFuncdef = {
1+IsStat4, /* nArg */
SQLITE_UTF8, /* funcFlags */
0, /* pUserData */
0, /* pNext */
statGet, /* xSFunc */
0, /* xFinalize */
0, 0, /* xValue, xInverse */
"stat_get", /* zName */
{0}
};
static void callStatGet(Parse *pParse, int regStat, int iParam, int regOut){
#ifdef SQLITE_ENABLE_STAT4
sqlite3VdbeAddOp2(pParse->pVdbe, OP_Integer, iParam, regStat+1);
#elif SQLITE_DEBUG
assert( iParam==STAT_GET_STAT1 );
#else
UNUSED_PARAMETER( iParam );
#endif
assert( regOut!=regStat && regOut!=regStat+1 );
sqlite3VdbeAddFunctionCall(pParse, 0, regStat, regOut, 1+IsStat4,
&statGetFuncdef, 0);
}
#ifdef SQLITE_ENABLE_EXPLAIN_COMMENTS
/* Add a comment to the most recent VDBE opcode that is the name
** of the k-th column of the pIdx index.
*/
static void analyzeVdbeCommentIndexWithColumnName(
Vdbe *v, /* Prepared statement under construction */
Index *pIdx, /* Index whose column is being loaded */
int k /* Which column index */
){
int i; /* Index of column in the table */
assert( k>=0 && k<pIdx->nColumn );
i = pIdx->aiColumn[k];
if( NEVER(i==XN_ROWID) ){
VdbeComment((v,"%s.rowid",pIdx->zName));
}else if( i==XN_EXPR ){
VdbeComment((v,"%s.expr(%d)",pIdx->zName, k));
}else{
VdbeComment((v,"%s.%s", pIdx->zName, pIdx->pTable->aCol[i].zName));
}
}
#else
# define analyzeVdbeCommentIndexWithColumnName(a,b,c)
#endif /* SQLITE_DEBUG */
/*
** Generate code to do an analysis of all indices associated with
** a single table.
*/
static void analyzeOneTable(
Parse *pParse, /* Parser context */
Table *pTab, /* Table whose indices are to be analyzed */
Index *pOnlyIdx, /* If not NULL, only analyze this one index */
int iStatCur, /* Index of VdbeCursor that writes the sqlite_stat1 table */
int iMem, /* Available memory locations begin here */
int iTab /* Next available cursor */
){
sqlite3 *db = pParse->db; /* Database handle */
Index *pIdx; /* An index to being analyzed */
int iIdxCur; /* Cursor open on index being analyzed */
int iTabCur; /* Table cursor */
Vdbe *v; /* The virtual machine being built up */
int i; /* Loop counter */
int jZeroRows = -1; /* Jump from here if number of rows is zero */
int iDb; /* Index of database containing pTab */
u8 needTableCnt = 1; /* True to count the table */
int regNewRowid = iMem++; /* Rowid for the inserted record */
int regStat = iMem++; /* Register to hold StatAccum object */
int regChng = iMem++; /* Index of changed index field */
int regRowid = iMem++; /* Rowid argument passed to stat_push() */
int regTemp = iMem++; /* Temporary use register */
int regTemp2 = iMem++; /* Second temporary use register */
int regTabname = iMem++; /* Register containing table name */
int regIdxname = iMem++; /* Register containing index name */
int regStat1 = iMem++; /* Value for the stat column of sqlite_stat1 */
int regPrev = iMem; /* MUST BE LAST (see below) */
#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
Table *pStat1 = 0;
#endif
pParse->nMem = MAX(pParse->nMem, iMem);
v = sqlite3GetVdbe(pParse);
if( v==0 || NEVER(pTab==0) ){
return;
}
if( pTab->tnum==0 ){
/* Do not gather statistics on views or virtual tables */
return;
}
if( sqlite3_strlike("sqlite\\_%", pTab->zName, '\\')==0 ){
/* Do not gather statistics on system tables */
return;
}
assert( sqlite3BtreeHoldsAllMutexes(db) );
iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
assert( iDb>=0 );
assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
#ifndef SQLITE_OMIT_AUTHORIZATION
if( sqlite3AuthCheck(pParse, SQLITE_ANALYZE, pTab->zName, 0,
db->aDb[iDb].zDbSName ) ){
return;
}
#endif
#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
if( db->xPreUpdateCallback ){
pStat1 = (Table*)sqlite3DbMallocZero(db, sizeof(Table) + 13);
if( pStat1==0 ) return;
pStat1->zName = (char*)&pStat1[1];
memcpy(pStat1->zName, "sqlite_stat1", 13);
pStat1->nCol = 3;
pStat1->iPKey = -1;
sqlite3VdbeAddOp4(pParse->pVdbe, OP_Noop, 0, 0, 0,(char*)pStat1,P4_DYNBLOB);
}
#endif
/* Establish a read-lock on the table at the shared-cache level.
** Open a read-only cursor on the table. Also allocate a cursor number
** to use for scanning indexes (iIdxCur). No index cursor is opened at
** this time though. */
sqlite3TableLock(pParse, iDb, pTab->tnum, 0, pTab->zName);
iTabCur = iTab++;
iIdxCur = iTab++;
pParse->nTab = MAX(pParse->nTab, iTab);
sqlite3OpenTable(pParse, iTabCur, iDb, pTab, OP_OpenRead);
sqlite3VdbeLoadString(v, regTabname, pTab->zName);
for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
int nCol; /* Number of columns in pIdx. "N" */
int addrRewind; /* Address of "OP_Rewind iIdxCur" */
int addrNextRow; /* Address of "next_row:" */
const char *zIdxName; /* Name of the index */
int nColTest; /* Number of columns to test for changes */
if( pOnlyIdx && pOnlyIdx!=pIdx ) continue;
if( pIdx->pPartIdxWhere==0 ) needTableCnt = 0;
if( !HasRowid(pTab) && IsPrimaryKeyIndex(pIdx) ){
nCol = pIdx->nKeyCol;
zIdxName = pTab->zName;
nColTest = nCol - 1;
}else{
nCol = pIdx->nColumn;
zIdxName = pIdx->zName;
nColTest = pIdx->uniqNotNull ? pIdx->nKeyCol-1 : nCol-1;
}
/* Populate the register containing the index name. */
sqlite3VdbeLoadString(v, regIdxname, zIdxName);
VdbeComment((v, "Analysis for %s.%s", pTab->zName, zIdxName));
/*
** Pseudo-code for loop that calls stat_push():
**
** Rewind csr
** if eof(csr) goto end_of_scan;
** regChng = 0
** goto chng_addr_0;
**
** next_row:
** regChng = 0
** if( idx(0) != regPrev(0) ) goto chng_addr_0
** regChng = 1
** if( idx(1) != regPrev(1) ) goto chng_addr_1
** ...
** regChng = N
** goto chng_addr_N
**
** chng_addr_0:
** regPrev(0) = idx(0)
** chng_addr_1:
** regPrev(1) = idx(1)
** ...
**
** endDistinctTest:
** regRowid = idx(rowid)
** stat_push(P, regChng, regRowid)
** Next csr
** if !eof(csr) goto next_row;
**
** end_of_scan:
*/
/* Make sure there are enough memory cells allocated to accommodate
** the regPrev array and a trailing rowid (the rowid slot is required
** when building a record to insert into the sample column of
** the sqlite_stat4 table. */
pParse->nMem = MAX(pParse->nMem, regPrev+nColTest);
/* Open a read-only cursor on the index being analyzed. */
assert( iDb==sqlite3SchemaToIndex(db, pIdx->pSchema) );
sqlite3VdbeAddOp3(v, OP_OpenRead, iIdxCur, pIdx->tnum, iDb);
sqlite3VdbeSetP4KeyInfo(pParse, pIdx);
VdbeComment((v, "%s", pIdx->zName));
/* Invoke the stat_init() function. The arguments are:
**
** (1) the number of columns in the index including the rowid
** (or for a WITHOUT ROWID table, the number of PK columns),
** (2) the number of columns in the key without the rowid/pk
** (3) estimated number of rows in the index,
*/
sqlite3VdbeAddOp2(v, OP_Integer, nCol, regStat+1);
assert( regRowid==regStat+2 );
sqlite3VdbeAddOp2(v, OP_Integer, pIdx->nKeyCol, regRowid);
#ifdef SQLITE_ENABLE_STAT4
if( OptimizationEnabled(db, SQLITE_Stat4) ){
sqlite3VdbeAddOp2(v, OP_Count, iIdxCur, regTemp);
addrRewind = sqlite3VdbeAddOp1(v, OP_Rewind, iIdxCur);
VdbeCoverage(v);
}else
#endif
{
addrRewind = sqlite3VdbeAddOp1(v, OP_Rewind, iIdxCur);
VdbeCoverage(v);
sqlite3VdbeAddOp3(v, OP_Count, iIdxCur, regTemp, 1);
}
assert( regTemp2==regStat+4 );
sqlite3VdbeAddOp2(v, OP_Integer, db->nAnalysisLimit, regTemp2);
sqlite3VdbeAddFunctionCall(pParse, 0, regStat+1, regStat, 4,
&statInitFuncdef, 0);
/* Implementation of the following:
**
** Rewind csr
** if eof(csr) goto end_of_scan;
** regChng = 0
** goto next_push_0;
**
*/
sqlite3VdbeAddOp2(v, OP_Integer, 0, regChng);
addrNextRow = sqlite3VdbeCurrentAddr(v);
if( nColTest>0 ){
int endDistinctTest = sqlite3VdbeMakeLabel(pParse);
int *aGotoChng; /* Array of jump instruction addresses */
aGotoChng = sqlite3DbMallocRawNN(db, sizeof(int)*nColTest);
if( aGotoChng==0 ) continue;
/*
** next_row:
** regChng = 0
** if( idx(0) != regPrev(0) ) goto chng_addr_0
** regChng = 1
** if( idx(1) != regPrev(1) ) goto chng_addr_1
** ...
** regChng = N
** goto endDistinctTest
*/
sqlite3VdbeAddOp0(v, OP_Goto);
addrNextRow = sqlite3VdbeCurrentAddr(v);
if( nColTest==1 && pIdx->nKeyCol==1 && IsUniqueIndex(pIdx) ){
/* For a single-column UNIQUE index, once we have found a non-NULL
** row, we know that all the rest will be distinct, so skip
** subsequent distinctness tests. */
sqlite3VdbeAddOp2(v, OP_NotNull, regPrev, endDistinctTest);
VdbeCoverage(v);
}
for(i=0; i<nColTest; i++){
char *pColl = (char*)sqlite3LocateCollSeq(pParse, pIdx->azColl[i]);
sqlite3VdbeAddOp2(v, OP_Integer, i, regChng);
sqlite3VdbeAddOp3(v, OP_Column, iIdxCur, i, regTemp);
analyzeVdbeCommentIndexWithColumnName(v,pIdx,i);
aGotoChng[i] =
sqlite3VdbeAddOp4(v, OP_Ne, regTemp, 0, regPrev+i, pColl, P4_COLLSEQ);
sqlite3VdbeChangeP5(v, SQLITE_NULLEQ);
VdbeCoverage(v);
}
sqlite3VdbeAddOp2(v, OP_Integer, nColTest, regChng);
sqlite3VdbeGoto(v, endDistinctTest);
/*
** chng_addr_0:
** regPrev(0) = idx(0)
** chng_addr_1:
** regPrev(1) = idx(1)
** ...
*/
sqlite3VdbeJumpHere(v, addrNextRow-1);
for(i=0; i<nColTest; i++){
sqlite3VdbeJumpHere(v, aGotoChng[i]);
sqlite3VdbeAddOp3(v, OP_Column, iIdxCur, i, regPrev+i);
analyzeVdbeCommentIndexWithColumnName(v,pIdx,i);
}
sqlite3VdbeResolveLabel(v, endDistinctTest);
sqlite3DbFree(db, aGotoChng);
}
/*
** chng_addr_N:
** regRowid = idx(rowid) // STAT4 only
** stat_push(P, regChng, regRowid) // 3rd parameter STAT4 only
** Next csr
** if !eof(csr) goto next_row;
*/
#ifdef SQLITE_ENABLE_STAT4
if( OptimizationEnabled(db, SQLITE_Stat4) ){
assert( regRowid==(regStat+2) );
if( HasRowid(pTab) ){
sqlite3VdbeAddOp2(v, OP_IdxRowid, iIdxCur, regRowid);
}else{
Index *pPk = sqlite3PrimaryKeyIndex(pIdx->pTable);
int j, k, regKey;
regKey = sqlite3GetTempRange(pParse, pPk->nKeyCol);
for(j=0; j<pPk->nKeyCol; j++){
k = sqlite3TableColumnToIndex(pIdx, pPk->aiColumn[j]);
assert( k>=0 && k<pIdx->nColumn );
sqlite3VdbeAddOp3(v, OP_Column, iIdxCur, k, regKey+j);
analyzeVdbeCommentIndexWithColumnName(v,pIdx,k);
}
sqlite3VdbeAddOp3(v, OP_MakeRecord, regKey, pPk->nKeyCol, regRowid);
sqlite3ReleaseTempRange(pParse, regKey, pPk->nKeyCol);
}
}
#endif
assert( regChng==(regStat+1) );
{
sqlite3VdbeAddFunctionCall(pParse, 1, regStat, regTemp, 2+IsStat4,
&statPushFuncdef, 0);
if( db->nAnalysisLimit ){
int j1, j2, j3;
j1 = sqlite3VdbeAddOp1(v, OP_IsNull, regTemp); VdbeCoverage(v);
j2 = sqlite3VdbeAddOp1(v, OP_If, regTemp); VdbeCoverage(v);
j3 = sqlite3VdbeAddOp4Int(v, OP_SeekGT, iIdxCur, 0, regPrev, 1);
VdbeCoverage(v);
sqlite3VdbeJumpHere(v, j1);
sqlite3VdbeAddOp2(v, OP_Next, iIdxCur, addrNextRow); VdbeCoverage(v);
sqlite3VdbeJumpHere(v, j2);
sqlite3VdbeJumpHere(v, j3);
}else{
sqlite3VdbeAddOp2(v, OP_Next, iIdxCur, addrNextRow); VdbeCoverage(v);
}
}
/* Add the entry to the stat1 table. */
callStatGet(pParse, regStat, STAT_GET_STAT1, regStat1);
assert( "BBB"[0]==SQLITE_AFF_TEXT );
sqlite3VdbeAddOp4(v, OP_MakeRecord, regTabname, 3, regTemp, "BBB", 0);
sqlite3VdbeAddOp2(v, OP_NewRowid, iStatCur, regNewRowid);
sqlite3VdbeAddOp3(v, OP_Insert, iStatCur, regTemp, regNewRowid);
#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
sqlite3VdbeChangeP4(v, -1, (char*)pStat1, P4_TABLE);
#endif
sqlite3VdbeChangeP5(v, OPFLAG_APPEND);
/* Add the entries to the stat4 table. */
#ifdef SQLITE_ENABLE_STAT4
if( OptimizationEnabled(db, SQLITE_Stat4) && db->nAnalysisLimit==0 ){
int regEq = regStat1;
int regLt = regStat1+1;
int regDLt = regStat1+2;
int regSample = regStat1+3;
int regCol = regStat1+4;
int regSampleRowid = regCol + nCol;
int addrNext;
int addrIsNull;
u8 seekOp = HasRowid(pTab) ? OP_NotExists : OP_NotFound;
pParse->nMem = MAX(pParse->nMem, regCol+nCol);
addrNext = sqlite3VdbeCurrentAddr(v);
callStatGet(pParse, regStat, STAT_GET_ROWID, regSampleRowid);
addrIsNull = sqlite3VdbeAddOp1(v, OP_IsNull, regSampleRowid);
VdbeCoverage(v);
callStatGet(pParse, regStat, STAT_GET_NEQ, regEq);
callStatGet(pParse, regStat, STAT_GET_NLT, regLt);
callStatGet(pParse, regStat, STAT_GET_NDLT, regDLt);
sqlite3VdbeAddOp4Int(v, seekOp, iTabCur, addrNext, regSampleRowid, 0);
VdbeCoverage(v);
for(i=0; i<nCol; i++){
sqlite3ExprCodeLoadIndexColumn(pParse, pIdx, iTabCur, i, regCol+i);
}
sqlite3VdbeAddOp3(v, OP_MakeRecord, regCol, nCol, regSample);
sqlite3VdbeAddOp3(v, OP_MakeRecord, regTabname, 6, regTemp);
sqlite3VdbeAddOp2(v, OP_NewRowid, iStatCur+1, regNewRowid);
sqlite3VdbeAddOp3(v, OP_Insert, iStatCur+1, regTemp, regNewRowid);
sqlite3VdbeAddOp2(v, OP_Goto, 1, addrNext); /* P1==1 for end-of-loop */
sqlite3VdbeJumpHere(v, addrIsNull);
}
#endif /* SQLITE_ENABLE_STAT4 */
/* End of analysis */
sqlite3VdbeJumpHere(v, addrRewind);
}
/* Create a single sqlite_stat1 entry containing NULL as the index
** name and the row count as the content.
*/
if( pOnlyIdx==0 && needTableCnt ){
VdbeComment((v, "%s", pTab->zName));
sqlite3VdbeAddOp2(v, OP_Count, iTabCur, regStat1);
jZeroRows = sqlite3VdbeAddOp1(v, OP_IfNot, regStat1); VdbeCoverage(v);
sqlite3VdbeAddOp2(v, OP_Null, 0, regIdxname);
assert( "BBB"[0]==SQLITE_AFF_TEXT );
sqlite3VdbeAddOp4(v, OP_MakeRecord, regTabname, 3, regTemp, "BBB", 0);
sqlite3VdbeAddOp2(v, OP_NewRowid, iStatCur, regNewRowid);
sqlite3VdbeAddOp3(v, OP_Insert, iStatCur, regTemp, regNewRowid);
sqlite3VdbeChangeP5(v, OPFLAG_APPEND);
#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
sqlite3VdbeChangeP4(v, -1, (char*)pStat1, P4_TABLE);
#endif
sqlite3VdbeJumpHere(v, jZeroRows);
}
}
/*
** Generate code that will cause the most recent index analysis to
** be loaded into internal hash tables where is can be used.
*/
static void loadAnalysis(Parse *pParse, int iDb){
Vdbe *v = sqlite3GetVdbe(pParse);
if( v ){
sqlite3VdbeAddOp1(v, OP_LoadAnalysis, iDb);
}
}
/*
** Generate code that will do an analysis of an entire database
*/
static void analyzeDatabase(Parse *pParse, int iDb){
sqlite3 *db = pParse->db;
Schema *pSchema = db->aDb[iDb].pSchema; /* Schema of database iDb */
HashElem *k;
int iStatCur;
int iMem;
int iTab;
sqlite3BeginWriteOperation(pParse, 0, iDb);
iStatCur = pParse->nTab;
pParse->nTab += 3;
openStatTable(pParse, iDb, iStatCur, 0, 0);
iMem = pParse->nMem+1;
iTab = pParse->nTab;
assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
for(k=sqliteHashFirst(&pSchema->tblHash); k; k=sqliteHashNext(k)){
Table *pTab = (Table*)sqliteHashData(k);
analyzeOneTable(pParse, pTab, 0, iStatCur, iMem, iTab);
}
loadAnalysis(pParse, iDb);
}
/*
** Generate code that will do an analysis of a single table in
** a database. If pOnlyIdx is not NULL then it is a single index
** in pTab that should be analyzed.
*/
static void analyzeTable(Parse *pParse, Table *pTab, Index *pOnlyIdx){
int iDb;
int iStatCur;
assert( pTab!=0 );
assert( sqlite3BtreeHoldsAllMutexes(pParse->db) );
iDb = sqlite3SchemaToIndex(pParse->db, pTab->pSchema);
sqlite3BeginWriteOperation(pParse, 0, iDb);
iStatCur = pParse->nTab;
pParse->nTab += 3;
if( pOnlyIdx ){
openStatTable(pParse, iDb, iStatCur, pOnlyIdx->zName, "idx");
}else{
openStatTable(pParse, iDb, iStatCur, pTab->zName, "tbl");
}
analyzeOneTable(pParse, pTab, pOnlyIdx, iStatCur,pParse->nMem+1,pParse->nTab);
loadAnalysis(pParse, iDb);
}
/*
** Generate code for the ANALYZE command. The parser calls this routine
** when it recognizes an ANALYZE command.
**
** ANALYZE -- 1
** ANALYZE <database> -- 2
** ANALYZE ?<database>.?<tablename> -- 3
**
** Form 1 causes all indices in all attached databases to be analyzed.
** Form 2 analyzes all indices the single database named.
** Form 3 analyzes all indices associated with the named table.
*/
void sqlite3Analyze(Parse *pParse, Token *pName1, Token *pName2){
sqlite3 *db = pParse->db;
int iDb;
int i;
char *z, *zDb;
Table *pTab;
Index *pIdx;
Token *pTableName;
Vdbe *v;
/* Read the database schema. If an error occurs, leave an error message
** and code in pParse and return NULL. */
assert( sqlite3BtreeHoldsAllMutexes(pParse->db) );
if( SQLITE_OK!=sqlite3ReadSchema(pParse) ){
return;
}
assert( pName2!=0 || pName1==0 );
if( pName1==0 ){
/* Form 1: Analyze everything */
for(i=0; i<db->nDb; i++){
if( i==1 ) continue; /* Do not analyze the TEMP database */
analyzeDatabase(pParse, i);
}
}else if( pName2->n==0 && (iDb = sqlite3FindDb(db, pName1))>=0 ){
/* Analyze the schema named as the argument */
analyzeDatabase(pParse, iDb);
}else{
/* Form 3: Analyze the table or index named as an argument */
iDb = sqlite3TwoPartName(pParse, pName1, pName2, &pTableName);
if( iDb>=0 ){
zDb = pName2->n ? db->aDb[iDb].zDbSName : 0;
z = sqlite3NameFromToken(db, pTableName);
if( z ){
if( (pIdx = sqlite3FindIndex(db, z, zDb))!=0 ){
analyzeTable(pParse, pIdx->pTable, pIdx);
}else if( (pTab = sqlite3LocateTable(pParse, 0, z, zDb))!=0 ){
analyzeTable(pParse, pTab, 0);
}
sqlite3DbFree(db, z);
}
}
}
if( db->nSqlExec==0 && (v = sqlite3GetVdbe(pParse))!=0 ){
sqlite3VdbeAddOp0(v, OP_Expire);
}
}
/*
** Used to pass information from the analyzer reader through to the
** callback routine.
*/
typedef struct analysisInfo analysisInfo;
struct analysisInfo {
sqlite3 *db;
const char *zDatabase;
};
/*
** The first argument points to a nul-terminated string containing a
** list of space separated integers. Read the first nOut of these into
** the array aOut[].
*/
static void decodeIntArray(
char *zIntArray, /* String containing int array to decode */
int nOut, /* Number of slots in aOut[] */
tRowcnt *aOut, /* Store integers here */
LogEst *aLog, /* Or, if aOut==0, here */
Index *pIndex /* Handle extra flags for this index, if not NULL */
){
char *z = zIntArray;
int c;
int i;
tRowcnt v;
#ifdef SQLITE_ENABLE_STAT4
if( z==0 ) z = "";
#else
assert( z!=0 );
#endif
for(i=0; *z && i<nOut; i++){
v = 0;
while( (c=z[0])>='0' && c<='9' ){
v = v*10 + c - '0';
z++;
}
#ifdef SQLITE_ENABLE_STAT4
if( aOut ) aOut[i] = v;
if( aLog ) aLog[i] = sqlite3LogEst(v);
#else
assert( aOut==0 );
UNUSED_PARAMETER(aOut);
assert( aLog!=0 );
aLog[i] = sqlite3LogEst(v);
#endif
if( *z==' ' ) z++;
}
#ifndef SQLITE_ENABLE_STAT4
assert( pIndex!=0 ); {
#else
if( pIndex ){
#endif
pIndex->bUnordered = 0;
pIndex->noSkipScan = 0;
while( z[0] ){
if( sqlite3_strglob("unordered*", z)==0 ){
pIndex->bUnordered = 1;
}else if( sqlite3_strglob("sz=[0-9]*", z)==0 ){
int sz = sqlite3Atoi(z+3);
if( sz<2 ) sz = 2;
pIndex->szIdxRow = sqlite3LogEst(sz);
}else if( sqlite3_strglob("noskipscan*", z)==0 ){
pIndex->noSkipScan = 1;
}
#ifdef SQLITE_ENABLE_COSTMULT
else if( sqlite3_strglob("costmult=[0-9]*",z)==0 ){
pIndex->pTable->costMult = sqlite3LogEst(sqlite3Atoi(z+9));
}
#endif
while( z[0]!=0 && z[0]!=' ' ) z++;
while( z[0]==' ' ) z++;
}
}
}
/*
** This callback is invoked once for each index when reading the
** sqlite_stat1 table.
**
** argv[0] = name of the table
** argv[1] = name of the index (might be NULL)
** argv[2] = results of analysis - on integer for each column
**
** Entries for which argv[1]==NULL simply record the number of rows in
** the table.
*/
static int analysisLoader(void *pData, int argc, char **argv, char **NotUsed){
analysisInfo *pInfo = (analysisInfo*)pData;
Index *pIndex;
Table *pTable;
const char *z;
assert( argc==3 );
UNUSED_PARAMETER2(NotUsed, argc);
if( argv==0 || argv[0]==0 || argv[2]==0 ){
return 0;
}
pTable = sqlite3FindTable(pInfo->db, argv[0], pInfo->zDatabase);
if( pTable==0 ){
return 0;
}
if( argv[1]==0 ){
pIndex = 0;
}else if( sqlite3_stricmp(argv[0],argv[1])==0 ){
pIndex = sqlite3PrimaryKeyIndex(pTable);
}else{
pIndex = sqlite3FindIndex(pInfo->db, argv[1], pInfo->zDatabase);
}
z = argv[2];
if( pIndex ){
tRowcnt *aiRowEst = 0;
int nCol = pIndex->nKeyCol+1;
#ifdef SQLITE_ENABLE_STAT4
/* Index.aiRowEst may already be set here if there are duplicate
** sqlite_stat1 entries for this index. In that case just clobber
** the old data with the new instead of allocating a new array. */
if( pIndex->aiRowEst==0 ){
pIndex->aiRowEst = (tRowcnt*)sqlite3MallocZero(sizeof(tRowcnt) * nCol);
if( pIndex->aiRowEst==0 ) sqlite3OomFault(pInfo->db);
}
aiRowEst = pIndex->aiRowEst;
#endif
pIndex->bUnordered = 0;
decodeIntArray((char*)z, nCol, aiRowEst, pIndex->aiRowLogEst, pIndex);
pIndex->hasStat1 = 1;
if( pIndex->pPartIdxWhere==0 ){
pTable->nRowLogEst = pIndex->aiRowLogEst[0];
pTable->tabFlags |= TF_HasStat1;
}
}else{
Index fakeIdx;
fakeIdx.szIdxRow = pTable->szTabRow;
#ifdef SQLITE_ENABLE_COSTMULT
fakeIdx.pTable = pTable;
#endif
decodeIntArray((char*)z, 1, 0, &pTable->nRowLogEst, &fakeIdx);
pTable->szTabRow = fakeIdx.szIdxRow;
pTable->tabFlags |= TF_HasStat1;
}
return 0;
}
/*
** If the Index.aSample variable is not NULL, delete the aSample[] array
** and its contents.
*/
void sqlite3DeleteIndexSamples(sqlite3 *db, Index *pIdx){
#ifdef SQLITE_ENABLE_STAT4
if( pIdx->aSample ){
int j;
for(j=0; j<pIdx->nSample; j++){
IndexSample *p = &pIdx->aSample[j];
sqlite3DbFree(db, p->p);
}
sqlite3DbFree(db, pIdx->aSample);
}
if( db && db->pnBytesFreed==0 ){
pIdx->nSample = 0;
pIdx->aSample = 0;
}
#else
UNUSED_PARAMETER(db);
UNUSED_PARAMETER(pIdx);
#endif /* SQLITE_ENABLE_STAT4 */
}
#ifdef SQLITE_ENABLE_STAT4
/*
** Populate the pIdx->aAvgEq[] array based on the samples currently
** stored in pIdx->aSample[].
*/
static void initAvgEq(Index *pIdx){
if( pIdx ){
IndexSample *aSample = pIdx->aSample;
IndexSample *pFinal = &aSample[pIdx->nSample-1];
int iCol;
int nCol = 1;
if( pIdx->nSampleCol>1 ){
/* If this is stat4 data, then calculate aAvgEq[] values for all
** sample columns except the last. The last is always set to 1, as
** once the trailing PK fields are considered all index keys are
** unique. */
nCol = pIdx->nSampleCol-1;
pIdx->aAvgEq[nCol] = 1;
}
for(iCol=0; iCol<nCol; iCol++){
int nSample = pIdx->nSample;
int i; /* Used to iterate through samples */
tRowcnt sumEq = 0; /* Sum of the nEq values */
tRowcnt avgEq = 0;
tRowcnt nRow; /* Number of rows in index */
i64 nSum100 = 0; /* Number of terms contributing to sumEq */
i64 nDist100; /* Number of distinct values in index */
if( !pIdx->aiRowEst || iCol>=pIdx->nKeyCol || pIdx->aiRowEst[iCol+1]==0 ){
nRow = pFinal->anLt[iCol];
nDist100 = (i64)100 * pFinal->anDLt[iCol];
nSample--;
}else{
nRow = pIdx->aiRowEst[0];
nDist100 = ((i64)100 * pIdx->aiRowEst[0]) / pIdx->aiRowEst[iCol+1];
}
pIdx->nRowEst0 = nRow;
/* Set nSum to the number of distinct (iCol+1) field prefixes that
** occur in the stat4 table for this index. Set sumEq to the sum of
** the nEq values for column iCol for the same set (adding the value
** only once where there exist duplicate prefixes). */
for(i=0; i<nSample; i++){
if( i==(pIdx->nSample-1)
|| aSample[i].anDLt[iCol]!=aSample[i+1].anDLt[iCol]
){
sumEq += aSample[i].anEq[iCol];
nSum100 += 100;
}
}
if( nDist100>nSum100 && sumEq<nRow ){
avgEq = ((i64)100 * (nRow - sumEq))/(nDist100 - nSum100);
}
if( avgEq==0 ) avgEq = 1;
pIdx->aAvgEq[iCol] = avgEq;
}
}
}
/*
** Look up an index by name. Or, if the name of a WITHOUT ROWID table
** is supplied instead, find the PRIMARY KEY index for that table.
*/
static Index *findIndexOrPrimaryKey(
sqlite3 *db,
const char *zName,
const char *zDb
){
Index *pIdx = sqlite3FindIndex(db, zName, zDb);
if( pIdx==0 ){
Table *pTab = sqlite3FindTable(db, zName, zDb);
if( pTab && !HasRowid(pTab) ) pIdx = sqlite3PrimaryKeyIndex(pTab);
}
return pIdx;
}
/*
** Load the content from either the sqlite_stat4
** into the relevant Index.aSample[] arrays.
**
** Arguments zSql1 and zSql2 must point to SQL statements that return
** data equivalent to the following:
**
** zSql1: SELECT idx,count(*) FROM %Q.sqlite_stat4 GROUP BY idx
** zSql2: SELECT idx,neq,nlt,ndlt,sample FROM %Q.sqlite_stat4
**
** where %Q is replaced with the database name before the SQL is executed.
*/
static int loadStatTbl(
sqlite3 *db, /* Database handle */
const char *zSql1, /* SQL statement 1 (see above) */
const char *zSql2, /* SQL statement 2 (see above) */
const char *zDb /* Database name (e.g. "main") */
){
int rc; /* Result codes from subroutines */
sqlite3_stmt *pStmt = 0; /* An SQL statement being run */
char *zSql; /* Text of the SQL statement */
Index *pPrevIdx = 0; /* Previous index in the loop */
IndexSample *pSample; /* A slot in pIdx->aSample[] */
assert( db->lookaside.bDisable );
zSql = sqlite3MPrintf(db, zSql1, zDb);
if( !zSql ){
return SQLITE_NOMEM_BKPT;
}
rc = sqlite3_prepare(db, zSql, -1, &pStmt, 0);
sqlite3DbFree(db, zSql);
if( rc ) return rc;
while( sqlite3_step(pStmt)==SQLITE_ROW ){
int nIdxCol = 1; /* Number of columns in stat4 records */
char *zIndex; /* Index name */
Index *pIdx; /* Pointer to the index object */
int nSample; /* Number of samples */
int nByte; /* Bytes of space required */
int i; /* Bytes of space required */
tRowcnt *pSpace;
zIndex = (char *)sqlite3_column_text(pStmt, 0);
if( zIndex==0 ) continue;
nSample = sqlite3_column_int(pStmt, 1);
pIdx = findIndexOrPrimaryKey(db, zIndex, zDb);
assert( pIdx==0 || pIdx->nSample==0 );
if( pIdx==0 ) continue;
assert( !HasRowid(pIdx->pTable) || pIdx->nColumn==pIdx->nKeyCol+1 );
if( !HasRowid(pIdx->pTable) && IsPrimaryKeyIndex(pIdx) ){
nIdxCol = pIdx->nKeyCol;
}else{
nIdxCol = pIdx->nColumn;
}
pIdx->nSampleCol = nIdxCol;
nByte = sizeof(IndexSample) * nSample;
nByte += sizeof(tRowcnt) * nIdxCol * 3 * nSample;
nByte += nIdxCol * sizeof(tRowcnt); /* Space for Index.aAvgEq[] */
pIdx->aSample = sqlite3DbMallocZero(db, nByte);
if( pIdx->aSample==0 ){
sqlite3_finalize(pStmt);
return SQLITE_NOMEM_BKPT;
}
pSpace = (tRowcnt*)&pIdx->aSample[nSample];
pIdx->aAvgEq = pSpace; pSpace += nIdxCol;
pIdx->pTable->tabFlags |= TF_HasStat4;
for(i=0; i<nSample; i++){
pIdx->aSample[i].anEq = pSpace; pSpace += nIdxCol;
pIdx->aSample[i].anLt = pSpace; pSpace += nIdxCol;
pIdx->aSample[i].anDLt = pSpace; pSpace += nIdxCol;
}
assert( ((u8*)pSpace)-nByte==(u8*)(pIdx->aSample) );
}
rc = sqlite3_finalize(pStmt);
if( rc ) return rc;
zSql = sqlite3MPrintf(db, zSql2, zDb);
if( !zSql ){
return SQLITE_NOMEM_BKPT;
}
rc = sqlite3_prepare(db, zSql, -1, &pStmt, 0);
sqlite3DbFree(db, zSql);
if( rc ) return rc;
while( sqlite3_step(pStmt)==SQLITE_ROW ){
char *zIndex; /* Index name */
Index *pIdx; /* Pointer to the index object */
int nCol = 1; /* Number of columns in index */
zIndex = (char *)sqlite3_column_text(pStmt, 0);
if( zIndex==0 ) continue;
pIdx = findIndexOrPrimaryKey(db, zIndex, zDb);
if( pIdx==0 ) continue;
/* This next condition is true if data has already been loaded from
** the sqlite_stat4 table. */
nCol = pIdx->nSampleCol;
if( pIdx!=pPrevIdx ){
initAvgEq(pPrevIdx);
pPrevIdx = pIdx;
}
pSample = &pIdx->aSample[pIdx->nSample];
decodeIntArray((char*)sqlite3_column_text(pStmt,1),nCol,pSample->anEq,0,0);
decodeIntArray((char*)sqlite3_column_text(pStmt,2),nCol,pSample->anLt,0,0);
decodeIntArray((char*)sqlite3_column_text(pStmt,3),nCol,pSample->anDLt,0,0);
/* Take a copy of the sample. Add two 0x00 bytes the end of the buffer.
** This is in case the sample record is corrupted. In that case, the
** sqlite3VdbeRecordCompare() may read up to two varints past the
** end of the allocated buffer before it realizes it is dealing with
** a corrupt record. Adding the two 0x00 bytes prevents this from causing
** a buffer overread. */
pSample->n = sqlite3_column_bytes(pStmt, 4);
pSample->p = sqlite3DbMallocZero(db, pSample->n + 2);
if( pSample->p==0 ){
sqlite3_finalize(pStmt);
return SQLITE_NOMEM_BKPT;
}
if( pSample->n ){
memcpy(pSample->p, sqlite3_column_blob(pStmt, 4), pSample->n);
}
pIdx->nSample++;
}
rc = sqlite3_finalize(pStmt);
if( rc==SQLITE_OK ) initAvgEq(pPrevIdx);
return rc;
}
/*
** Load content from the sqlite_stat4 table into
** the Index.aSample[] arrays of all indices.
*/
static int loadStat4(sqlite3 *db, const char *zDb){
int rc = SQLITE_OK; /* Result codes from subroutines */
assert( db->lookaside.bDisable );
if( sqlite3FindTable(db, "sqlite_stat4", zDb) ){
rc = loadStatTbl(db,
"SELECT idx,count(*) FROM %Q.sqlite_stat4 GROUP BY idx",
"SELECT idx,neq,nlt,ndlt,sample FROM %Q.sqlite_stat4",
zDb
);
}
return rc;
}
#endif /* SQLITE_ENABLE_STAT4 */
/*
** Load the content of the sqlite_stat1 and sqlite_stat4 tables. The
** contents of sqlite_stat1 are used to populate the Index.aiRowEst[]
** arrays. The contents of sqlite_stat4 are used to populate the
** Index.aSample[] arrays.
**
** If the sqlite_stat1 table is not present in the database, SQLITE_ERROR
** is returned. In this case, even if SQLITE_ENABLE_STAT4 was defined
** during compilation and the sqlite_stat4 table is present, no data is
** read from it.
**
** If SQLITE_ENABLE_STAT4 was defined during compilation and the
** sqlite_stat4 table is not present in the database, SQLITE_ERROR is
** returned. However, in this case, data is read from the sqlite_stat1
** table (if it is present) before returning.
**
** If an OOM error occurs, this function always sets db->mallocFailed.
** This means if the caller does not care about other errors, the return
** code may be ignored.
*/
int sqlite3AnalysisLoad(sqlite3 *db, int iDb){
analysisInfo sInfo;
HashElem *i;
char *zSql;
int rc = SQLITE_OK;
Schema *pSchema = db->aDb[iDb].pSchema;
assert( iDb>=0 && iDb<db->nDb );
assert( db->aDb[iDb].pBt!=0 );
/* Clear any prior statistics */
assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
for(i=sqliteHashFirst(&pSchema->tblHash); i; i=sqliteHashNext(i)){
Table *pTab = sqliteHashData(i);
pTab->tabFlags &= ~TF_HasStat1;
}
for(i=sqliteHashFirst(&pSchema->idxHash); i; i=sqliteHashNext(i)){
Index *pIdx = sqliteHashData(i);
pIdx->hasStat1 = 0;
#ifdef SQLITE_ENABLE_STAT4
sqlite3DeleteIndexSamples(db, pIdx);
pIdx->aSample = 0;
#endif
}
/* Load new statistics out of the sqlite_stat1 table */
sInfo.db = db;
sInfo.zDatabase = db->aDb[iDb].zDbSName;
if( sqlite3FindTable(db, "sqlite_stat1", sInfo.zDatabase)!=0 ){
zSql = sqlite3MPrintf(db,
"SELECT tbl,idx,stat FROM %Q.sqlite_stat1", sInfo.zDatabase);
if( zSql==0 ){
rc = SQLITE_NOMEM_BKPT;
}else{
rc = sqlite3_exec(db, zSql, analysisLoader, &sInfo, 0);
sqlite3DbFree(db, zSql);
}
}
/* Set appropriate defaults on all indexes not in the sqlite_stat1 table */
assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
for(i=sqliteHashFirst(&pSchema->idxHash); i; i=sqliteHashNext(i)){
Index *pIdx = sqliteHashData(i);
if( !pIdx->hasStat1 ) sqlite3DefaultRowEst(pIdx);
}
/* Load the statistics from the sqlite_stat4 table. */
#ifdef SQLITE_ENABLE_STAT4
if( rc==SQLITE_OK ){
DisableLookaside;
rc = loadStat4(db, sInfo.zDatabase);
EnableLookaside;
}
for(i=sqliteHashFirst(&pSchema->idxHash); i; i=sqliteHashNext(i)){
Index *pIdx = sqliteHashData(i);
sqlite3_free(pIdx->aiRowEst);
pIdx->aiRowEst = 0;
}
#endif
if( rc==SQLITE_NOMEM ){
sqlite3OomFault(db);
}
return rc;
}
#endif /* SQLITE_OMIT_ANALYZE */
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