/*
** 2005 July 8
**
** 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.
**
** @(#) $Id: analyze.c,v 1.16 2006/01/10 17:58:23 danielk1977 Exp $
*/
#ifndef SQLITE_OMIT_ANALYZE
#include "sqliteInt.h"
/*
** This routine generates code that opens the sqlite_stat1 table on cursor
** iStatCur.
**
** If the sqlite_stat1 tables does not previously exist, it is created.
** If it does previously exist, all entires associated with table zWhere
** are removed. If zWhere==0 then all entries are removed.
*/
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 associated with this table */
){
sqlite3 *db = pParse->db;
Db *pDb;
int iRootPage;
Table *pStat;
Vdbe *v = sqlite3GetVdbe(pParse);
pDb = &db->aDb[iDb];
if( (pStat = sqlite3FindTable(db, "sqlite_stat1", pDb->zName))==0 ){
/* The sqlite_stat1 tables does not exist. Create it.
** Note that a side-effect of the CREATE TABLE statement is to leave
** the rootpage of the new table on the top of the stack. This is
** important because the OpenWrite opcode below will be needing it. */
sqlite3NestedParse(pParse,
"CREATE TABLE %Q.sqlite_stat1(tbl,idx,stat)",
pDb->zName
);
iRootPage = 0; /* Cause rootpage to be taken from top of stack */
}else if( zWhere ){
/* The sqlite_stat1 table exists. Delete all entries associated with
** the table zWhere. */
sqlite3NestedParse(pParse,
"DELETE FROM %Q.sqlite_stat1 WHERE tbl=%Q",
pDb->zName, zWhere
);
iRootPage = pStat->tnum;
}else{
/* The sqlite_stat1 table already exists. Delete all rows. */
iRootPage = pStat->tnum;
sqlite3VdbeAddOp(v, OP_Clear, pStat->tnum, iDb);
}
/* Open the sqlite_stat1 table for writing. Unless it was created
** by this vdbe program, lock it for writing at the shared-cache level.
** If this vdbe did create the sqlite_stat1 table, then it must have
** already obtained a schema-lock, making the write-lock redundant.
*/
if( iRootPage>0 ){
sqlite3TableLock(pParse, iDb, iRootPage, 1, "sqlite_stat1");
}
sqlite3VdbeAddOp(v, OP_Integer, iDb, 0);
sqlite3VdbeAddOp(v, OP_OpenWrite, iStatCur, iRootPage);
sqlite3VdbeAddOp(v, OP_SetNumColumns, iStatCur, 3);
}
/*
** 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 */
int iStatCur, /* Cursor that writes to the sqlite_stat1 table */
int iMem /* Available memory locations begin here */
){
Index *pIdx; /* An index to being analyzed */
int iIdxCur; /* Cursor number for index being analyzed */
int nCol; /* Number of columns in the index */
Vdbe *v; /* The virtual machine being built up */
int i; /* Loop counter */
int topOfLoop; /* The top of the loop */
int endOfLoop; /* The end of the loop */
int addr; /* The address of an instruction */
int iDb; /* Index of database containing pTab */
v = sqlite3GetVdbe(pParse);
if( pTab==0 || pTab->pIndex==0 ){
/* Do no analysis for tables that have no indices */
return;
}
iDb = sqlite3SchemaToIndex(pParse->db, pTab->pSchema);
assert( iDb>=0 );
#ifndef SQLITE_OMIT_AUTHORIZATION
if( sqlite3AuthCheck(pParse, SQLITE_ANALYZE, pTab->zName, 0,
pParse->db->aDb[iDb].zName ) ){
return;
}
#endif
/* Establish a read-lock on the table at the shared-cache level. */
sqlite3TableLock(pParse, iDb, pTab->tnum, 0, pTab->zName);
iIdxCur = pParse->nTab;
for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
KeyInfo *pKey = sqlite3IndexKeyinfo(pParse, pIdx);
/* Open a cursor to the index to be analyzed
*/
assert( iDb==sqlite3SchemaToIndex(pParse->db, pIdx->pSchema) );
sqlite3VdbeAddOp(v, OP_Integer, iDb, 0);
VdbeComment((v, "# %s", pIdx->zName));
sqlite3VdbeOp3(v, OP_OpenRead, iIdxCur, pIdx->tnum,
(char *)pKey, P3_KEYINFO_HANDOFF);
nCol = pIdx->nColumn;
if( iMem+nCol*2>=pParse->nMem ){
pParse->nMem = iMem+nCol*2+1;
}
sqlite3VdbeAddOp(v, OP_SetNumColumns, iIdxCur, nCol+1);
/* Memory cells are used as follows:
**
** mem[iMem]: The total number of rows in the table.
** mem[iMem+1]: Number of distinct values in column 1
** ...
** mem[iMem+nCol]: Number of distinct values in column N
** mem[iMem+nCol+1] Last observed value of column 1
** ...
** mem[iMem+nCol+nCol]: Last observed value of column N
**
** Cells iMem through iMem+nCol are initialized to 0. The others
** are initialized to NULL.
*/
for(i=0; i<=nCol; i++){
sqlite3VdbeAddOp(v, OP_MemInt, 0, iMem+i);
}
for(i=0; i<nCol; i++){
sqlite3VdbeAddOp(v, OP_MemNull, iMem+nCol+i+1, 0);
}
/* Do the analysis.
*/
endOfLoop = sqlite3VdbeMakeLabel(v);
sqlite3VdbeAddOp(v, OP_Rewind, iIdxCur, endOfLoop);
topOfLoop = sqlite3VdbeCurrentAddr(v);
sqlite3VdbeAddOp(v, OP_MemIncr, 1, iMem);
for(i=0; i<nCol; i++){
sqlite3VdbeAddOp(v, OP_Column, iIdxCur, i);
sqlite3VdbeAddOp(v, OP_MemLoad, iMem+nCol+i+1, 0);
sqlite3VdbeAddOp(v, OP_Ne, 0x100, 0);
}
sqlite3VdbeAddOp(v, OP_Goto, 0, endOfLoop);
for(i=0; i<nCol; i++){
addr = sqlite3VdbeAddOp(v, OP_MemIncr, 1, iMem+i+1);
sqlite3VdbeChangeP2(v, topOfLoop + 3*i + 3, addr);
sqlite3VdbeAddOp(v, OP_Column, iIdxCur, i);
sqlite3VdbeAddOp(v, OP_MemStore, iMem+nCol+i+1, 1);
}
sqlite3VdbeResolveLabel(v, endOfLoop);
sqlite3VdbeAddOp(v, OP_Next, iIdxCur, topOfLoop);
sqlite3VdbeAddOp(v, OP_Close, iIdxCur, 0);
/* Store the results.
**
** The result is a single row of the sqlite_stmt1 table. The first
** two columns are the names of the table and index. The third column
** is a string composed of a list of integer statistics about the
** index. The first integer in the list is the total number of entires
** in the index. There is one additional integer in the list for each
** column of the table. This additional integer is a guess of how many
** rows of the table the index will select. If D is the count of distinct
** values and K is the total number of rows, then the integer is computed
** as:
**
** I = (K+D-1)/D
**
** If K==0 then no entry is made into the sqlite_stat1 table.
** If K>0 then it is always the case the D>0 so division by zero
** is never possible.
*/
sqlite3VdbeAddOp(v, OP_MemLoad, iMem, 0);
addr = sqlite3VdbeAddOp(v, OP_IfNot, 0, 0);
sqlite3VdbeAddOp(v, OP_NewRowid, iStatCur, 0);
sqlite3VdbeOp3(v, OP_String8, 0, 0, pTab->zName, 0);
sqlite3VdbeOp3(v, OP_String8, 0, 0, pIdx->zName, 0);
sqlite3VdbeAddOp(v, OP_MemLoad, iMem, 0);
sqlite3VdbeOp3(v, OP_String8, 0, 0, " ", 0);
for(i=0; i<nCol; i++){
sqlite3VdbeAddOp(v, OP_MemLoad, iMem, 0);
sqlite3VdbeAddOp(v, OP_MemLoad, iMem+i+1, 0);
sqlite3VdbeAddOp(v, OP_Add, 0, 0);
sqlite3VdbeAddOp(v, OP_AddImm, -1, 0);
sqlite3VdbeAddOp(v, OP_MemLoad, iMem+i+1, 0);
sqlite3VdbeAddOp(v, OP_Divide, 0, 0);
sqlite3VdbeAddOp(v, OP_ToInt, 0, 0);
if( i==nCol-1 ){
sqlite3VdbeAddOp(v, OP_Concat, nCol*2-1, 0);
}else{
sqlite3VdbeAddOp(v, OP_Dup, 1, 0);
}
}
sqlite3VdbeOp3(v, OP_MakeRecord, 3, 0, "aaa", 0);
sqlite3VdbeAddOp(v, OP_Insert, iStatCur, 0);
sqlite3VdbeJumpHere(v, addr);
}
}
/*
** Generate code that will cause the most recent index analysis to
** be laoded into internal hash tables where is can be used.
*/
static void loadAnalysis(Parse *pParse, int iDb){
Vdbe *v = sqlite3GetVdbe(pParse);
sqlite3VdbeAddOp(v, OP_LoadAnalysis, iDb, 0);
}
/*
** 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;
sqlite3BeginWriteOperation(pParse, 0, iDb);
iStatCur = pParse->nTab++;
openStatTable(pParse, iDb, iStatCur, 0);
iMem = pParse->nMem;
for(k=sqliteHashFirst(&pSchema->tblHash); k; k=sqliteHashNext(k)){
Table *pTab = (Table*)sqliteHashData(k);
analyzeOneTable(pParse, pTab, iStatCur, iMem);
}
loadAnalysis(pParse, iDb);
}
/*
** Generate code that will do an analysis of a single table in
** a database.
*/
static void analyzeTable(Parse *pParse, Table *pTab){
int iDb;
int iStatCur;
assert( pTab!=0 );
iDb = sqlite3SchemaToIndex(pParse->db, pTab->pSchema);
sqlite3BeginWriteOperation(pParse, 0, iDb);
iStatCur = pParse->nTab++;
openStatTable(pParse, iDb, iStatCur, pTab->zName);
analyzeOneTable(pParse, pTab, iStatCur, pParse->nMem);
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;
Token *pTableName;
/* Read the database schema. If an error occurs, leave an error message
** and code in pParse and return NULL. */
if( SQLITE_OK!=sqlite3ReadSchema(pParse) ){
return;
}
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==0 || pName2->n==0 ){
/* Form 2: Analyze the database or table named */
iDb = sqlite3FindDb(db, pName1);
if( iDb>=0 ){
analyzeDatabase(pParse, iDb);
}else{
z = sqlite3NameFromToken(pName1);
pTab = sqlite3LocateTable(pParse, z, 0);
sqliteFree(z);
if( pTab ){
analyzeTable(pParse, pTab);
}
}
}else{
/* Form 3: Analyze the fully qualified table name */
iDb = sqlite3TwoPartName(pParse, pName1, pName2, &pTableName);
if( iDb>=0 ){
zDb = db->aDb[iDb].zName;
z = sqlite3NameFromToken(pTableName);
pTab = sqlite3LocateTable(pParse, z, zDb);
sqliteFree(z);
if( pTab ){
analyzeTable(pParse, pTab);
}
}
}
}
/*
** Used to pass information from the analyzer reader through to the
** callback routine.
*/
typedef struct analysisInfo analysisInfo;
struct analysisInfo {
sqlite3 *db;
const char *zDatabase;
};
/*
** This callback is invoked once for each index when reading the
** sqlite_stat1 table.
**
** argv[0] = name of the index
** argv[1] = results of analysis - on integer for each column
*/
static int analysisLoader(void *pData, int argc, char **argv, char **azNotUsed){
analysisInfo *pInfo = (analysisInfo*)pData;
Index *pIndex;
int i, c;
unsigned int v;
const char *z;
assert( argc==2 );
if( argv==0 || argv[0]==0 || argv[1]==0 ){
return 0;
}
pIndex = sqlite3FindIndex(pInfo->db, argv[0], pInfo->zDatabase);
if( pIndex==0 ){
return 0;
}
z = argv[1];
for(i=0; *z && i<=pIndex->nColumn; i++){
v = 0;
while( (c=z[0])>='0' && c<='9' ){
v = v*10 + c - '0';
z++;
}
pIndex->aiRowEst[i] = v;
if( *z==' ' ) z++;
}
return 0;
}
/*
** Load the content of the sqlite_stat1 table into the index hash tables.
*/
void sqlite3AnalysisLoad(sqlite3 *db, int iDb){
analysisInfo sInfo;
HashElem *i;
char *zSql;
/* Clear any prior statistics */
for(i=sqliteHashFirst(&db->aDb[iDb].pSchema->idxHash);i;i=sqliteHashNext(i)){
Index *pIdx = sqliteHashData(i);
sqlite3DefaultRowEst(pIdx);
}
/* Check to make sure the sqlite_stat1 table existss */
sInfo.db = db;
sInfo.zDatabase = db->aDb[iDb].zName;
if( sqlite3FindTable(db, "sqlite_stat1", sInfo.zDatabase)==0 ){
return;
}
/* Load new statistics out of the sqlite_stat1 table */
zSql = sqlite3MPrintf("SELECT idx, stat FROM %Q.sqlite_stat1",
sInfo.zDatabase);
sqlite3SafetyOff(db);
sqlite3_exec(db, zSql, analysisLoader, &sInfo, 0);
sqlite3SafetyOn(db);
sqliteFree(zSql);
}
#endif /* SQLITE_OMIT_ANALYZE */
Submit an article or tip