1 /*

     2 ** 2005 July 8

     3 **

     4 ** The author disclaims copyright to this source code.  In place of

     5 ** a legal notice, here is a blessing:

     6 **

     7 **    May you do good and not evil.

     8 **    May you find forgiveness for yourself and forgive others.

     9 **    May you share freely, never taking more than you give.

    10 **

    11 *************************************************************************

    12 ** This file contains code associated with the ANALYZE command.

    13 **

    14 ** @(#) $Id: analyze.c,v 1.16 2006/01/10 17:58:23 danielk1977 Exp $

    15 */

    16 #ifndef SQLITE_OMIT_ANALYZE

    17 #include "sqliteInt.h"

    18 

    19 /*

    20 ** This routine generates code that opens the sqlite_stat1 table on cursor

    21 ** iStatCur.

    22 **

    23 ** If the sqlite_stat1 tables does not previously exist, it is created.

    24 ** If it does previously exist, all entires associated with table zWhere

    25 ** are removed.  If zWhere==0 then all entries are removed.

    26 */

    27 static void openStatTable(

    28   Parse *pParse,          /* Parsing context */

    29   int iDb,                /* The database we are looking in */

    30   int iStatCur,           /* Open the sqlite_stat1 table on this cursor */

    31   const char *zWhere      /* Delete entries associated with this table */

    32 ){

    33   sqlite3 *db = pParse->db;

    34   Db *pDb;

    35   int iRootPage;

    36   Table *pStat;

    37   Vdbe *v = sqlite3GetVdbe(pParse);

    38 

    39   pDb = &db->aDb[iDb];

    40   if( (pStat = sqlite3FindTable(db, "sqlite_stat1", pDb->zName))==0 ){

    41     /* The sqlite_stat1 tables does not exist.  Create it.  

    42     ** Note that a side-effect of the CREATE TABLE statement is to leave

    43     ** the rootpage of the new table on the top of the stack.  This is

    44     ** important because the OpenWrite opcode below will be needing it. */

    45     sqlite3NestedParse(pParse,

    46       "CREATE TABLE %Q.sqlite_stat1(tbl,idx,stat)",

    47       pDb->zName

    48     );

    49     iRootPage = 0;  /* Cause rootpage to be taken from top of stack */

    50   }else if( zWhere ){

    51     /* The sqlite_stat1 table exists.  Delete all entries associated with

    52     ** the table zWhere. */

    53     sqlite3NestedParse(pParse,

    54        "DELETE FROM %Q.sqlite_stat1 WHERE tbl=%Q",

    55        pDb->zName, zWhere

    56     );

    57     iRootPage = pStat->tnum;

    58   }else{

    59     /* The sqlite_stat1 table already exists.  Delete all rows. */

    60     iRootPage = pStat->tnum;

    61     sqlite3VdbeAddOp(v, OP_Clear, pStat->tnum, iDb);

    62   }

    63 

    64   /* Open the sqlite_stat1 table for writing. Unless it was created

    65   ** by this vdbe program, lock it for writing at the shared-cache level. 

    66   ** If this vdbe did create the sqlite_stat1 table, then it must have 

    67   ** already obtained a schema-lock, making the write-lock redundant.

    68   */

    69   if( iRootPage>0 ){

    70     sqlite3TableLock(pParse, iDb, iRootPage, 1, "sqlite_stat1");

    71   }

    72   sqlite3VdbeAddOp(v, OP_Integer, iDb, 0);

    73   sqlite3VdbeAddOp(v, OP_OpenWrite, iStatCur, iRootPage);

    74   sqlite3VdbeAddOp(v, OP_SetNumColumns, iStatCur, 3);

    75 }

    76 

    77 /*

    78 ** Generate code to do an analysis of all indices associated with

    79 ** a single table.

    80 */

    81 static void analyzeOneTable(

    82   Parse *pParse,   /* Parser context */

    83   Table *pTab,     /* Table whose indices are to be analyzed */

    84   int iStatCur,    /* Cursor that writes to the sqlite_stat1 table */

    85   int iMem         /* Available memory locations begin here */

    86 ){

    87   Index *pIdx;     /* An index to being analyzed */

    88   int iIdxCur;     /* Cursor number for index being analyzed */

    89   int nCol;        /* Number of columns in the index */

    90   Vdbe *v;         /* The virtual machine being built up */

    91   int i;           /* Loop counter */

    92   int topOfLoop;   /* The top of the loop */

    93   int endOfLoop;   /* The end of the loop */

    94   int addr;        /* The address of an instruction */

    95   int iDb;         /* Index of database containing pTab */

    96 

    97   v = sqlite3GetVdbe(pParse);

    98   if( pTab==0 || pTab->pIndex==0 ){

    99     /* Do no analysis for tables that have no indices */

   100     return;

   101   }

   102 

   103   iDb = sqlite3SchemaToIndex(pParse->db, pTab->pSchema);

   104   assert( iDb>=0 );

   105 #ifndef SQLITE_OMIT_AUTHORIZATION

   106   if( sqlite3AuthCheck(pParse, SQLITE_ANALYZE, pTab->zName, 0,

   107       pParse->db->aDb[iDb].zName ) ){

   108     return;

   109   }

   110 #endif

   111 

   112   /* Establish a read-lock on the table at the shared-cache level. */

   113   sqlite3TableLock(pParse, iDb, pTab->tnum, 0, pTab->zName);

   114 

   115   iIdxCur = pParse->nTab;

   116   for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){

   117     KeyInfo *pKey = sqlite3IndexKeyinfo(pParse, pIdx);

   118 

   119     /* Open a cursor to the index to be analyzed

   120     */

   121     assert( iDb==sqlite3SchemaToIndex(pParse->db, pIdx->pSchema) );

   122     sqlite3VdbeAddOp(v, OP_Integer, iDb, 0);

   123     VdbeComment((v, "# %s", pIdx->zName));

   124     sqlite3VdbeOp3(v, OP_OpenRead, iIdxCur, pIdx->tnum,

   125         (char *)pKey, P3_KEYINFO_HANDOFF);

   126     nCol = pIdx->nColumn;

   127     if( iMem+nCol*2>=pParse->nMem ){

   128       pParse->nMem = iMem+nCol*2+1;

   129     }

   130     sqlite3VdbeAddOp(v, OP_SetNumColumns, iIdxCur, nCol+1);

   131 

   132     /* Memory cells are used as follows:

   133     **

   134     **    mem[iMem]:             The total number of rows in the table.

   135     **    mem[iMem+1]:           Number of distinct values in column 1

   136     **    ...

   137     **    mem[iMem+nCol]:        Number of distinct values in column N

   138     **    mem[iMem+nCol+1]       Last observed value of column 1

   139     **    ...

   140     **    mem[iMem+nCol+nCol]:   Last observed value of column N

   141     **

   142     ** Cells iMem through iMem+nCol are initialized to 0.  The others

   143     ** are initialized to NULL.

   144     */

   145     for(i=0; i<=nCol; i++){

   146       sqlite3VdbeAddOp(v, OP_MemInt, 0, iMem+i);

   147     }

   148     for(i=0; i<nCol; i++){

   149       sqlite3VdbeAddOp(v, OP_MemNull, iMem+nCol+i+1, 0);

   150     }

   151 

   152     /* Do the analysis.

   153     */

   154     endOfLoop = sqlite3VdbeMakeLabel(v);

   155     sqlite3VdbeAddOp(v, OP_Rewind, iIdxCur, endOfLoop);

   156     topOfLoop = sqlite3VdbeCurrentAddr(v);

   157     sqlite3VdbeAddOp(v, OP_MemIncr, 1, iMem);

   158     for(i=0; i<nCol; i++){

   159       sqlite3VdbeAddOp(v, OP_Column, iIdxCur, i);

   160       sqlite3VdbeAddOp(v, OP_MemLoad, iMem+nCol+i+1, 0);

   161       sqlite3VdbeAddOp(v, OP_Ne, 0x100, 0);

   162     }

   163     sqlite3VdbeAddOp(v, OP_Goto, 0, endOfLoop);

   164     for(i=0; i<nCol; i++){

   165       addr = sqlite3VdbeAddOp(v, OP_MemIncr, 1, iMem+i+1);

   166       sqlite3VdbeChangeP2(v, topOfLoop + 3*i + 3, addr);

   167       sqlite3VdbeAddOp(v, OP_Column, iIdxCur, i);

   168       sqlite3VdbeAddOp(v, OP_MemStore, iMem+nCol+i+1, 1);

   169     }

   170     sqlite3VdbeResolveLabel(v, endOfLoop);

   171     sqlite3VdbeAddOp(v, OP_Next, iIdxCur, topOfLoop);

   172     sqlite3VdbeAddOp(v, OP_Close, iIdxCur, 0);

   173 

   174     /* Store the results.  

   175     **

   176     ** The result is a single row of the sqlite_stmt1 table.  The first

   177     ** two columns are the names of the table and index.  The third column

   178     ** is a string composed of a list of integer statistics about the

   179     ** index.  The first integer in the list is the total number of entires

   180     ** in the index.  There is one additional integer in the list for each

   181     ** column of the table.  This additional integer is a guess of how many

   182     ** rows of the table the index will select.  If D is the count of distinct

   183     ** values and K is the total number of rows, then the integer is computed

   184     ** as:

   185     **

   186     **        I = (K+D-1)/D

   187     **

   188     ** If K==0 then no entry is made into the sqlite_stat1 table.  

   189     ** If K>0 then it is always the case the D>0 so division by zero

   190     ** is never possible.

   191     */

   192     sqlite3VdbeAddOp(v, OP_MemLoad, iMem, 0);

   193     addr = sqlite3VdbeAddOp(v, OP_IfNot, 0, 0);

   194     sqlite3VdbeAddOp(v, OP_NewRowid, iStatCur, 0);

   195     sqlite3VdbeOp3(v, OP_String8, 0, 0, pTab->zName, 0);

   196     sqlite3VdbeOp3(v, OP_String8, 0, 0, pIdx->zName, 0);

   197     sqlite3VdbeAddOp(v, OP_MemLoad, iMem, 0);

   198     sqlite3VdbeOp3(v, OP_String8, 0, 0, " ", 0);

   199     for(i=0; i<nCol; i++){

   200       sqlite3VdbeAddOp(v, OP_MemLoad, iMem, 0);

   201       sqlite3VdbeAddOp(v, OP_MemLoad, iMem+i+1, 0);

   202       sqlite3VdbeAddOp(v, OP_Add, 0, 0);

   203       sqlite3VdbeAddOp(v, OP_AddImm, -1, 0);

   204       sqlite3VdbeAddOp(v, OP_MemLoad, iMem+i+1, 0);

   205       sqlite3VdbeAddOp(v, OP_Divide, 0, 0);

   206       sqlite3VdbeAddOp(v, OP_ToInt, 0, 0);

   207       if( i==nCol-1 ){

   208         sqlite3VdbeAddOp(v, OP_Concat, nCol*2-1, 0);

   209       }else{

   210         sqlite3VdbeAddOp(v, OP_Dup, 1, 0);

   211       }

   212     }

   213     sqlite3VdbeOp3(v, OP_MakeRecord, 3, 0, "aaa", 0);

   214     sqlite3VdbeAddOp(v, OP_Insert, iStatCur, 0);

   215     sqlite3VdbeJumpHere(v, addr);

   216   }

   217 }

   218 

   219 /*

   220 ** Generate code that will cause the most recent index analysis to

   221 ** be laoded into internal hash tables where is can be used.

   222 */

   223 static void loadAnalysis(Parse *pParse, int iDb){

   224   Vdbe *v = sqlite3GetVdbe(pParse);

   225   sqlite3VdbeAddOp(v, OP_LoadAnalysis, iDb, 0);

   226 }

   227 

   228 /*

   229 ** Generate code that will do an analysis of an entire database

   230 */

   231 static void analyzeDatabase(Parse *pParse, int iDb){

   232   sqlite3 *db = pParse->db;

   233   Schema *pSchema = db->aDb[iDb].pSchema;    /* Schema of database iDb */

   234   HashElem *k;

   235   int iStatCur;

   236   int iMem;

   237 

   238   sqlite3BeginWriteOperation(pParse, 0, iDb);

   239   iStatCur = pParse->nTab++;

   240   openStatTable(pParse, iDb, iStatCur, 0);

   241   iMem = pParse->nMem;

   242   for(k=sqliteHashFirst(&pSchema->tblHash); k; k=sqliteHashNext(k)){

   243     Table *pTab = (Table*)sqliteHashData(k);

   244     analyzeOneTable(pParse, pTab, iStatCur, iMem);

   245   }

   246   loadAnalysis(pParse, iDb);

   247 }

   248 

   249 /*

   250 ** Generate code that will do an analysis of a single table in

   251 ** a database.

   252 */

   253 static void analyzeTable(Parse *pParse, Table *pTab){

   254   int iDb;

   255   int iStatCur;

   256 

   257   assert( pTab!=0 );

   258   iDb = sqlite3SchemaToIndex(pParse->db, pTab->pSchema);

   259   sqlite3BeginWriteOperation(pParse, 0, iDb);

   260   iStatCur = pParse->nTab++;

   261   openStatTable(pParse, iDb, iStatCur, pTab->zName);

   262   analyzeOneTable(pParse, pTab, iStatCur, pParse->nMem);

   263   loadAnalysis(pParse, iDb);

   264 }

   265 

   266 /*

   267 ** Generate code for the ANALYZE command.  The parser calls this routine

   268 ** when it recognizes an ANALYZE command.

   269 **

   270 **        ANALYZE                            -- 1

   271 **        ANALYZE  <database>                -- 2

   272 **        ANALYZE  ?<database>.?<tablename>  -- 3

   273 **

   274 ** Form 1 causes all indices in all attached databases to be analyzed.

   275 ** Form 2 analyzes all indices the single database named.

   276 ** Form 3 analyzes all indices associated with the named table.

   277 */

   278 void sqlite3Analyze(Parse *pParse, Token *pName1, Token *pName2){

   279   sqlite3 *db = pParse->db;

   280   int iDb;

   281   int i;

   282   char *z, *zDb;

   283   Table *pTab;

   284   Token *pTableName;

   285 

   286   /* Read the database schema. If an error occurs, leave an error message

   287   ** and code in pParse and return NULL. */

   288   if( SQLITE_OK!=sqlite3ReadSchema(pParse) ){

   289     return;

   290   }

   291 

   292   if( pName1==0 ){

   293     /* Form 1:  Analyze everything */

   294     for(i=0; i<db->nDb; i++){

   295       if( i==1 ) continue;  /* Do not analyze the TEMP database */

   296       analyzeDatabase(pParse, i);

   297     }

   298   }else if( pName2==0 || pName2->n==0 ){

   299     /* Form 2:  Analyze the database or table named */

   300     iDb = sqlite3FindDb(db, pName1);

   301     if( iDb>=0 ){

   302       analyzeDatabase(pParse, iDb);

   303     }else{

   304       z = sqlite3NameFromToken(pName1);

   305       pTab = sqlite3LocateTable(pParse, z, 0);

   306       sqliteFree(z);

   307       if( pTab ){

   308         analyzeTable(pParse, pTab);

   309       }

   310     }

   311   }else{

   312     /* Form 3: Analyze the fully qualified table name */

   313     iDb = sqlite3TwoPartName(pParse, pName1, pName2, &pTableName);

   314     if( iDb>=0 ){

   315       zDb = db->aDb[iDb].zName;

   316       z = sqlite3NameFromToken(pTableName);

   317       pTab = sqlite3LocateTable(pParse, z, zDb);

   318       sqliteFree(z);

   319       if( pTab ){

   320         analyzeTable(pParse, pTab);

   321       }

   322     }   

   323   }

   324 }

   325 

   326 /*

   327 ** Used to pass information from the analyzer reader through to the

   328 ** callback routine.

   329 */

   330 typedef struct analysisInfo analysisInfo;

   331 struct analysisInfo {

   332   sqlite3 *db;

   333   const char *zDatabase;

   334 };

   335 

   336 /*

   337 ** This callback is invoked once for each index when reading the

   338 ** sqlite_stat1 table.  

   339 **

   340 **     argv[0] = name of the index

   341 **     argv[1] = results of analysis - on integer for each column

   342 */

   343 static int analysisLoader(void *pData, int argc, char **argv, char **azNotUsed){

   344   analysisInfo *pInfo = (analysisInfo*)pData;

   345   Index *pIndex;

   346   int i, c;

   347   unsigned int v;

   348   const char *z;

   349 

   350   assert( argc==2 );

   351   if( argv==0 || argv[0]==0 || argv[1]==0 ){

   352     return 0;

   353   }

   354   pIndex = sqlite3FindIndex(pInfo->db, argv[0], pInfo->zDatabase);

   355   if( pIndex==0 ){

   356     return 0;

   357   }

   358   z = argv[1];

   359   for(i=0; *z && i<=pIndex->nColumn; i++){

   360     v = 0;

   361     while( (c=z[0])>='0' && c<='9' ){

   362       v = v*10 + c - '0';

   363       z++;

   364     }

   365     pIndex->aiRowEst[i] = v;

   366     if( *z==' ' ) z++;

   367   }

   368   return 0;

   369 }

   370 

   371 /*

   372 ** Load the content of the sqlite_stat1 table into the index hash tables.

   373 */

   374 void sqlite3AnalysisLoad(sqlite3 *db, int iDb){

   375   analysisInfo sInfo;

   376   HashElem *i;

   377   char *zSql;

   378 

   379   /* Clear any prior statistics */

   380   for(i=sqliteHashFirst(&db->aDb[iDb].pSchema->idxHash);i;i=sqliteHashNext(i)){

   381     Index *pIdx = sqliteHashData(i);

   382     sqlite3DefaultRowEst(pIdx);

   383   }

   384 

   385   /* Check to make sure the sqlite_stat1 table existss */

   386   sInfo.db = db;

   387   sInfo.zDatabase = db->aDb[iDb].zName;

   388   if( sqlite3FindTable(db, "sqlite_stat1", sInfo.zDatabase)==0 ){

   389      return;

   390   }

   391 

   392 

   393   /* Load new statistics out of the sqlite_stat1 table */

   394   zSql = sqlite3MPrintf("SELECT idx, stat FROM %Q.sqlite_stat1",

   395                         sInfo.zDatabase);

   396   sqlite3SafetyOff(db);

   397   sqlite3_exec(db, zSql, analysisLoader, &sInfo, 0);

   398   sqlite3SafetyOn(db);

   399   sqliteFree(zSql);

   400 }

   401 

   402 

   403 #endif /* SQLITE_OMIT_ANALYZE */