自学教程：C++ sqlite3NameFromToken函数代码示例

/*** 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;  /* 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 ){    /* Form 2:  Analyze the database or table named */    iDb = sqlite3FindDb(db, pName1);    if( iDb>=0 ){      analyzeDatabase(pParse, iDb);    }else{      z = sqlite3NameFromToken(db, pName1);      if( z ){        if( (pIdx = sqlite3FindIndex(db, z, 0))!=0 ){          analyzeTable(pParse, pIdx->pTable, pIdx);        }else if( (pTab = sqlite3LocateTable(pParse, 0, z, 0))!=0 ){          analyzeTable(pParse, pTab, 0);        }        sqlite3DbFree(db, z);      }    }  }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(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);      }    }     }}

/*** The parser calls this routine when it first sees a CREATE VIRTUAL TABLE** statement.  The module name has been parsed, but the optional list** of parameters that follow the module name are still pending.*/void sqlite3VtabBeginParse(  Parse *pParse,        /* Parsing context */  Token *pName1,        /* Name of new table, or database name */  Token *pName2,        /* Name of new table or NULL */  Token *pModuleName,   /* Name of the module for the virtual table */  int ifNotExists       /* No error if the table already exists */){  int iDb;              /* The database the table is being created in */  Table *pTable;        /* The new virtual table */  sqlite3 *db;          /* Database connection */  sqlite3StartTable(pParse, pName1, pName2, 0, 0, 1, ifNotExists);  pTable = pParse->pNewTable;  if( pTable==0 ) return;  assert( 0==pTable->pIndex );  db = pParse->db;  iDb = sqlite3SchemaToIndex(db, pTable->pSchema);  assert( iDb>=0 );  pTable->tabFlags |= TF_Virtual;  pTable->nModuleArg = 0;  addModuleArgument(db, pTable, sqlite3NameFromToken(db, pModuleName));  addModuleArgument(db, pTable, 0);  addModuleArgument(db, pTable, sqlite3DbStrDup(db, pTable->zName));  assert( (pParse->sNameToken.z==pName2->z && pName2->z!=0)       || (pParse->sNameToken.z==pName1->z && pName2->z==0)  );  pParse->sNameToken.n = (int)(      &pModuleName->z[pModuleName->n] - pParse->sNameToken.z  );#ifndef SQLITE_OMIT_AUTHORIZATION  /* Creating a virtual table invokes the authorization callback twice.  ** The first invocation, to obtain permission to INSERT a row into the  ** sqlite_master table, has already been made by sqlite3StartTable().  ** The second call, to obtain permission to create the table, is made now.  */  if( pTable->azModuleArg ){    sqlite3AuthCheck(pParse, SQLITE_CREATE_VTABLE, pTable->zName,             pTable->azModuleArg[0], pParse->db->aDb[iDb].zDbSName);  }#endif}

/*** The parser calls this routine when it first sees a CREATE VIRTUAL TABLE** statement.  The module name has been parsed, but the optional list** of parameters that follow the module name are still pending.*/void sqlite3VtabBeginParse(  Parse *pParse,        /* Parsing context */  Token *pName1,        /* Name of new table, or database name */  Token *pName2,        /* Name of new table or NULL */  Token *pModuleName    /* Name of the module for the virtual table */){  int iDb;              /* The database the table is being created in */  Table *pTable;        /* The new virtual table */#ifndef SQLITE_OMIT_SHARED_CACHE  if( sqlite3ThreadDataReadOnly()->useSharedData ){    sqlite3ErrorMsg(pParse, "Cannot use virtual tables in shared-cache mode");    return;  }#endif  sqlite3StartTable(pParse, pName1, pName2, 0, 0, 1, 0);  pTable = pParse->pNewTable;  if( pTable==0 || pParse->nErr ) return;  assert( 0==pTable->pIndex );  iDb = sqlite3SchemaToIndex(pParse->db, pTable->pSchema);  assert( iDb>=0 );  pTable->isVirtual = 1;  pTable->nModuleArg = 0;  addModuleArgument(pTable, sqlite3NameFromToken(pModuleName));  addModuleArgument(pTable, sqlite3StrDup(pParse->db->aDb[iDb].zName));  addModuleArgument(pTable, sqlite3StrDup(pTable->zName));  pParse->sNameToken.n = pModuleName->z + pModuleName->n - pName1->z;#ifndef SQLITE_OMIT_AUTHORIZATION  /* Creating a virtual table invokes the authorization callback twice.  ** The first invocation, to obtain permission to INSERT a row into the  ** sqlite_master table, has already been made by sqlite3StartTable().  ** The second call, to obtain permission to create the table, is made now.  */  if( pTable->azModuleArg ){    sqlite3AuthCheck(pParse, SQLITE_CREATE_VTABLE, pTable->zName,             pTable->azModuleArg[0], pParse->db->aDb[iDb].zName);  }#endif}

/*** This routine is called by the parser to process a DETACH statement:****    DETACH DATABASE dbname**** The pDbname argument is the name of the database in the DETACH statement.*/void sqlite3Detach(Parse *pParse, Token *pDbname){  int i;  sqlite3 *db;  Vdbe *v;  Db *pDb = 0;  char *zName;  v = sqlite3GetVdbe(pParse);  if( !v ) return;  sqlite3VdbeAddOp(v, OP_Expire, 0, 0);  sqlite3VdbeAddOp(v, OP_Halt, 0, 0);  if( pParse->explain ) return;  db = pParse->db;  zName = sqlite3NameFromToken(pDbname);  if( zName==0 ) return;  for(i=0; i<db->nDb; i++){    pDb = &db->aDb[i];    if( pDb->pBt==0 ) continue;    if( sqlite3StrICmp(pDb->zName, zName)==0 ) break;  }  if( i>=db->nDb ){    sqlite3ErrorMsg(pParse, "no such database: %z", zName);    return;  }  if( i<2 ){    sqlite3ErrorMsg(pParse, "cannot detach database %z", zName);    return;  }  sqliteFree(zName);  if( !db->autoCommit ){    sqlite3ErrorMsg(pParse, "cannot DETACH database within transaction");    pParse->rc = SQLITE_ERROR;    return;  }#ifndef SQLITE_OMIT_AUTHORIZATION  if( sqlite3AuthCheck(pParse,SQLITE_DETACH,db->aDb[i].zName,0,0)!=SQLITE_OK ){    return;  }#endif /* SQLITE_OMIT_AUTHORIZATION */  sqlite3BtreeClose(pDb->pBt);  pDb->pBt = 0;  sqlite3ResetInternalSchema(db, 0);}

/*** pEList is a list of expressions which are really the result set of the** a SELECT statement.  pE is a term in an ORDER BY or GROUP BY clause.** This routine checks to see if pE is a simple identifier which corresponds** to the AS-name of one of the terms of the expression list.  If it is,** this routine return an integer between 1 and N where N is the number of** elements in pEList, corresponding to the matching entry.  If there is** no match, or if pE is not a simple identifier, then this routine** return 0.**** pEList has been resolved.  pE has not.*/static int resolveAsName(  Parse *pParse,     /* Parsing context for error messages */  ExprList *pEList,  /* List of expressions to scan */  Expr *pE           /* Expression we are trying to match */){  int i;             /* Loop counter */  if( pE->op==TK_ID || (pE->op==TK_STRING && pE->token.z[0]!='/'') ){    sqlite3 *db = pParse->db;    char *zCol = sqlite3NameFromToken(db, &pE->token);    if( zCol==0 ){      return -1;    }    for(i=0; i<pEList->nExpr; i++){      char *zAs = pEList->a[i].zName;      if( zAs!=0 && sqlite3StrICmp(zAs, zCol)==0 ){        sqlite3DbFree(db, zCol);        return i+1;      }    }    sqlite3DbFree(db, zCol);  }  return 0;}

/*** Generate code to implement the "ALTER TABLE xxx RENAME TO yyy" ** command. */void sqlite3AlterRenameTable(  Parse *pParse,            /* Parser context. */  SrcList *pSrc,            /* The table to rename. */  Token *pName              /* The new table name. */){  int iDb;                  /* Database that contains the table */  char *zDb;                /* Name of database iDb */  Table *pTab;              /* Table being renamed */  char *zName = 0;          /* NULL-terminated version of pName */   sqlite3 *db = pParse->db; /* Database connection */  int nTabName;             /* Number of UTF-8 characters in zTabName */  const char *zTabName;     /* Original name of the table */  Vdbe *v;#ifndef SQLITE_OMIT_TRIGGER  char *zWhere = 0;         /* Where clause to locate temp triggers */#endif  int isVirtualRename = 0;  /* True if this is a v-table with an xRename() */    if( sqlite3MallocFailed() ) goto exit_rename_table;  assert( pSrc->nSrc==1 );  pTab = sqlite3LocateTable(pParse, pSrc->a[0].zName, pSrc->a[0].zDatabase);  if( !pTab ) goto exit_rename_table;  iDb = sqlite3SchemaToIndex(pParse->db, pTab->pSchema);  zDb = db->aDb[iDb].zName;  /* Get a NULL terminated version of the new table name. */  zName = sqlite3NameFromToken(pName);  if( !zName ) goto exit_rename_table;  /* Check that a table or index named 'zName' does not already exist  ** in database iDb. If so, this is an error.  */  if( sqlite3FindTable(db, zName, zDb) || sqlite3FindIndex(db, zName, zDb) ){    sqlite3ErrorMsg(pParse,         "there is already another table or index with this name: %s", zName);    goto exit_rename_table;  }  /* Make sure it is not a system table being altered, or a reserved name  ** that the table is being renamed to.  */  if( strlen(pTab->zName)>6 && 0==sqlite3StrNICmp(pTab->zName, "sqlite_", 7) ){    sqlite3ErrorMsg(pParse, "table %s may not be altered", pTab->zName);    goto exit_rename_table;  }  if( SQLITE_OK!=sqlite3CheckObjectName(pParse, zName) ){    goto exit_rename_table;  }#ifndef SQLITE_OMIT_AUTHORIZATION  /* Invoke the authorization callback. */  if( sqlite3AuthCheck(pParse, SQLITE_ALTER_TABLE, zDb, pTab->zName, 0) ){    goto exit_rename_table;  }#endif#ifndef SQLITE_OMIT_VIRTUALTABLE  if( sqlite3ViewGetColumnNames(pParse, pTab) ){    goto exit_rename_table;  }  if( IsVirtual(pTab) && pTab->pMod->pModule->xRename ){    isVirtualRename = 1;  }#endif  /* Begin a transaction and code the VerifyCookie for database iDb.   ** Then modify the schema cookie (since the ALTER TABLE modifies the  ** schema). Open a statement transaction if the table is a virtual  ** table.  */  v = sqlite3GetVdbe(pParse);  if( v==0 ){    goto exit_rename_table;  }  sqlite3BeginWriteOperation(pParse, isVirtualRename, iDb);  sqlite3ChangeCookie(db, v, iDb);  /* If this is a virtual table, invoke the xRename() function if  ** one is defined. The xRename() callback will modify the names  ** of any resources used by the v-table implementation (including other  ** SQLite tables) that are identified by the name of the virtual table.  */#ifndef SQLITE_OMIT_VIRTUALTABLE  if( isVirtualRename ){    sqlite3VdbeOp3(v, OP_String8, 0, 0, zName, 0);    sqlite3VdbeOp3(v, OP_VRename, 0, 0, (const char*)pTab->pVtab, P3_VTAB);  }#endif  /* figure out how many UTF-8 characters are in zName */  zTabName = pTab->zName;  nTabName = sqlite3Utf8CharLen(zTabName, -1);  /* Modify the sqlite_master table to use the new table name. */  sqlite3NestedParse(pParse,//.........这里部分代码省略.........

/*** Process a pragma statement.  **** Pragmas are of this form:****      PRAGMA [database.]id [= value]**** The identifier might also be a string.  The value is a string, and** identifier, or a number.  If minusFlag is true, then the value is** a number that was preceded by a minus sign.**** If the left side is "database.id" then pId1 is the database name** and pId2 is the id.  If the left side is just "id" then pId1 is the** id and pId2 is any empty string.*/void sqlite3Pragma(  Parse *pParse,   Token *pId1,        /* First part of [database.]id field */  Token *pId2,        /* Second part of [database.]id field, or NULL */  Token *pValue,      /* Token for <value>, or NULL */  int minusFlag       /* True if a '-' sign preceded <value> */){  char *zLeft = 0;       /* Nul-terminated UTF-8 string <id> */  char *zRight = 0;      /* Nul-terminated UTF-8 string <value>, or NULL */  const char *zDb = 0;   /* The database name */  Token *pId;            /* Pointer to <id> token */  int iDb;               /* Database index for <database> */  sqlite3 *db = pParse->db;  Db *pDb;  Vdbe *v = sqlite3GetVdbe(pParse);  if( v==0 ) return;  /* Interpret the [database.] part of the pragma statement. iDb is the  ** index of the database this pragma is being applied to in db.aDb[]. */  iDb = sqlite3TwoPartName(pParse, pId1, pId2, &pId);  if( iDb<0 ) return;  pDb = &db->aDb[iDb];  zLeft = sqlite3NameFromToken(pId);  if( !zLeft ) return;  if( minusFlag ){    zRight = sqlite3MPrintf("-%T", pValue);  }else{    zRight = sqlite3NameFromToken(pValue);  }  zDb = ((iDb>0)?pDb->zName:0);  if( sqlite3AuthCheck(pParse, SQLITE_PRAGMA, zLeft, zRight, zDb) ){    goto pragma_out;  } #ifndef SQLITE_OMIT_PAGER_PRAGMAS  /*  **  PRAGMA [database.]default_cache_size  **  PRAGMA [database.]default_cache_size=N  **  ** The first form reports the current persistent setting for the  ** page cache size.  The value returned is the maximum number of  ** pages in the page cache.  The second form sets both the current  ** page cache size value and the persistent page cache size value  ** stored in the database file.  **  ** The default cache size is stored in meta-value 2 of page 1 of the  ** database file.  The cache size is actually the absolute value of  ** this memory location.  The sign of meta-value 2 determines the  ** synchronous setting.  A negative value means synchronous is off  ** and a positive value means synchronous is on.  */  if( sqlite3StrICmp(zLeft,"default_cache_size")==0 ){    static const VdbeOpList getCacheSize[] = {      { OP_ReadCookie,  0, 2,        0},  /* 0 */      { OP_AbsValue,    0, 0,        0},      { OP_Dup,         0, 0,        0},      { OP_Integer,     0, 0,        0},      { OP_Ne,          0, 6,        0},      { OP_Integer,     0, 0,        0},  /* 5 */      { OP_Callback,    1, 0,        0},    };    int addr;    if( sqlite3ReadSchema(pParse) ) goto pragma_out;    if( !zRight ){      sqlite3VdbeSetNumCols(v, 1);      sqlite3VdbeSetColName(v, 0, COLNAME_NAME, "cache_size", P3_STATIC);      addr = sqlite3VdbeAddOpList(v, ArraySize(getCacheSize), getCacheSize);      sqlite3VdbeChangeP1(v, addr, iDb);      sqlite3VdbeChangeP1(v, addr+5, MAX_PAGES);    }else{      int size = atoi(zRight);      if( size<0 ) size = -size;      sqlite3BeginWriteOperation(pParse, 0, iDb);      sqlite3VdbeAddOp(v, OP_Integer, size, 0);      sqlite3VdbeAddOp(v, OP_ReadCookie, iDb, 2);      addr = sqlite3VdbeAddOp(v, OP_Integer, 0, 0);      sqlite3VdbeAddOp(v, OP_Ge, 0, addr+3);      sqlite3VdbeAddOp(v, OP_Negative, 0, 0);      sqlite3VdbeAddOp(v, OP_SetCookie, iDb, 2);      pDb->pSchema->cache_size = size;      sqlite3BtreeSetCacheSize(pDb->pBt, pDb->pSchema->cache_size);    }  }else//.........这里部分代码省略.........

/*** Generate code to implement the "ALTER TABLE xxx RENAME TO yyy"** command.*/void sqlite3AlterRenameTable(  Parse *pParse,            /* Parser context. */  SrcList *pSrc,            /* The table to rename. */  Token *pName              /* The new table name. */){  int iDb;                  /* Database that contains the table */  char *zDb;                /* Name of database iDb */  Table *pTab;              /* Table being renamed */  char *zName = 0;          /* NULL-terminated version of pName */  sqlite3 *db = pParse->db; /* Database connection */  int nTabName;             /* Number of UTF-8 characters in zTabName */  const char *zTabName;     /* Original name of the table */  Vdbe *v;#ifndef SQLITE_OMIT_TRIGGER  char *zWhere = 0;         /* Where clause to locate temp triggers */#endif  VTable *pVTab = 0;        /* Non-zero if this is a v-tab with an xRename() */  int savedDbFlags;         /* Saved value of db->flags */  savedDbFlags = db->flags;  if( NEVER(db->mallocFailed) ) goto exit_rename_table;  assert( pSrc->nSrc==1 );  assert( sqlite3BtreeHoldsAllMutexes(pParse->db) );  pTab = sqlite3LocateTableItem(pParse, 0, &pSrc->a[0]);  if( !pTab ) goto exit_rename_table;  iDb = sqlite3SchemaToIndex(pParse->db, pTab->pSchema);  zDb = db->aDb[iDb].zName;  db->flags |= SQLITE_PreferBuiltin;  /* Get a NULL terminated version of the new table name. */  zName = sqlite3NameFromToken(db, pName);  if( !zName ) goto exit_rename_table;  /* Check that a table or index named 'zName' does not already exist  ** in database iDb. If so, this is an error.  */  if( sqlite3FindTable(db, zName, zDb) || sqlite3FindIndex(db, zName, zDb) ){    sqlite3ErrorMsg(pParse,        "there is already another table or index with this name: %s", zName);    goto exit_rename_table;  }  /* Make sure it is not a system table being altered, or a reserved name  ** that the table is being renamed to.  */  if( SQLITE_OK!=isSystemTable(pParse, pTab->zName) ){    goto exit_rename_table;  }  if( SQLITE_OK!=sqlite3CheckObjectName(pParse, zName) ){ goto    exit_rename_table;  }#ifndef SQLITE_OMIT_VIEW  if( pTab->pSelect ){    sqlite3ErrorMsg(pParse, "view %s may not be altered", pTab->zName);    goto exit_rename_table;  }#endif#ifndef SQLITE_OMIT_AUTHORIZATION  /* Invoke the authorization callback. */  if( sqlite3AuthCheck(pParse, SQLITE_ALTER_TABLE, zDb, pTab->zName, 0) ){    goto exit_rename_table;  }#endif#ifndef SQLITE_OMIT_VIRTUALTABLE  if( sqlite3ViewGetColumnNames(pParse, pTab) ){    goto exit_rename_table;  }  if( IsVirtual(pTab) ){    pVTab = sqlite3GetVTable(db, pTab);    if( pVTab->pVtab->pModule->xRename==0 ){      pVTab = 0;    }  }#endif  /* Begin a transaction for database iDb.  ** Then modify the schema cookie (since the ALTER TABLE modifies the  ** schema). Open a statement transaction if the table is a virtual  ** table.  */  v = sqlite3GetVdbe(pParse);  if( v==0 ){    goto exit_rename_table;  }  sqlite3BeginWriteOperation(pParse, pVTab!=0, iDb);  sqlite3ChangeCookie(pParse, iDb);  /* If this is a virtual table, invoke the xRename() function if  ** one is defined. The xRename() callback will modify the names  ** of any resources used by the v-table implementation (including other  ** SQLite tables) that are identified by the name of the virtual table.  *///.........这里部分代码省略.........

/*** This procedure generates VDBE code for a single invocation of either the** sqlite_detach() or sqlite_attach() SQL user functions.*/static void codeAttach(  Parse *pParse,       /* The parser context */  int type,            /* Either SQLITE_ATTACH or SQLITE_DETACH */  const char *zFunc,   /* Either "sqlite_attach" or "sqlite_detach */  int nFunc,           /* Number of args to pass to zFunc */  Expr *pAuthArg,      /* Expression to pass to authorization callback */  Expr *pFilename,     /* Name of database file */  Expr *pDbname,       /* Name of the database to use internally */  Expr *pKey           /* Database key for encryption extension */){  int rc;  NameContext sName;  Vdbe *v;  FuncDef *pFunc;  sqlite3* db = pParse->db;#ifndef SQLITE_OMIT_AUTHORIZATION  assert( sqlite3ThreadDataReadOnly()->mallocFailed || pAuthArg );  if( pAuthArg ){    char *zAuthArg = sqlite3NameFromToken(&pAuthArg->span);    if( !zAuthArg ){      goto attach_end;    }    rc = sqlite3AuthCheck(pParse, type, zAuthArg, 0, 0);    sqliteFree(zAuthArg);    if(rc!=SQLITE_OK ){      goto attach_end;    }  }#endif /* SQLITE_OMIT_AUTHORIZATION */  memset(&sName, 0, sizeof(NameContext));  sName.pParse = pParse;  if(       SQLITE_OK!=(rc = resolveAttachExpr(&sName, pFilename)) ||      SQLITE_OK!=(rc = resolveAttachExpr(&sName, pDbname)) ||      SQLITE_OK!=(rc = resolveAttachExpr(&sName, pKey))  ){    pParse->nErr++;    goto attach_end;  }  v = sqlite3GetVdbe(pParse);  sqlite3ExprCode(pParse, pFilename);  sqlite3ExprCode(pParse, pDbname);  sqlite3ExprCode(pParse, pKey);  assert(v || sqlite3ThreadDataReadOnly()->mallocFailed);  if( v ){    sqlite3VdbeAddOp(v, OP_Function, 0, nFunc);    pFunc = sqlite3FindFunction(db, zFunc, strlen(zFunc), nFunc, SQLITE_UTF8,0);    sqlite3VdbeChangeP3(v, -1, (char *)pFunc, P3_FUNCDEF);    /* Code an OP_Expire. For an ATTACH statement, set P1 to true (expire this    ** statement only). For DETACH, set it to false (expire all existing    ** statements).    */    sqlite3VdbeAddOp(v, OP_Expire, (type==SQLITE_ATTACH), 0);  }  attach_end:  sqlite3ExprDelete(pFilename);  sqlite3ExprDelete(pDbname);  sqlite3ExprDelete(pKey);}

//.........这里部分代码省略.........        iDb = 1;    }        /* Ensure the table name matches database name and that the table exists */    if( db->mallocFailed ) goto trigger_cleanup;    assert( pTableName->nSrc==1 );    sqlite3FixInit(&sFix, pParse, iDb, "trigger", pName);    if( sqlite3FixSrcList(&sFix, pTableName) ){        goto trigger_cleanup;    }    pTab = sqlite3SrcListLookup(pParse, pTableName);    if( !pTab ){        /* The table does not exist. */        if( db->init.iDb==1 ){            /* Ticket #3810.             ** Normally, whenever a table is dropped, all associated triggers are             ** dropped too.  But if a TEMP trigger is created on a non-TEMP table             ** and the table is dropped by a different database connection, the             ** trigger is not visible to the database connection that does the             ** drop so the trigger cannot be dropped.  This results in an             ** "orphaned trigger" - a trigger whose associated table is missing.             */            db->init.orphanTrigger = 1;        }        goto trigger_cleanup;    }    if( IsVirtual(pTab) ){        sqlite3ErrorMsg(pParse, "cannot create triggers on virtual tables");        goto trigger_cleanup;    }        /* Check that the trigger name is not reserved and that no trigger of the     ** specified name exists */    zName = sqlite3NameFromToken(db, pName);    if( !zName || SQLITE_OK!=sqlite3CheckObjectName(pParse, zName) ){        goto trigger_cleanup;    }    assert( sqlite3SchemaMutexHeld(db, iDb, 0) );    if( sqlite3HashFind(&(db->aDb[iDb].pSchema->trigHash),                        zName, sqlite3Strlen30(zName)) ){        if( !noErr ){            sqlite3ErrorMsg(pParse, "trigger %T already exists", pName);        }else{            assert( !db->init.busy );            sqlite3CodeVerifySchema(pParse, iDb);        }        goto trigger_cleanup;    }        /* Do not create a trigger on a system table */    if( sqlite3StrNICmp(pTab->zName, "sqlite_", 7)==0 ){        sqlite3ErrorMsg(pParse, "cannot create trigger on system table");        pParse->nErr++;        goto trigger_cleanup;    }        /* INSTEAD of triggers are only for views and views only support INSTEAD     ** of triggers.     */    if( pTab->pSelect && tr_tm!=TK_INSTEAD ){        sqlite3ErrorMsg(pParse, "cannot create %s trigger on view: %S",                        (tr_tm == TK_BEFORE)?"BEFORE":"AFTER", pTableName, 0);        goto trigger_cleanup;    }    if( !pTab->pSelect && tr_tm==TK_INSTEAD ){        sqlite3ErrorMsg(pParse, "cannot create INSTEAD OF"

/*** Generate code to implement the "ALTER TABLE xxx RENAME TO yyy" ** command. 生成代码来实现“ALTER TABLE xxx重命名yyy”命令。*/void sqlite3AlterRenameTable(  Parse *pParse,            /* Parser context. 语法分析器上下文*/  SrcList *pSrc,            /* The table to rename. 重命名的表*/  Token *pName              /* The new table name. 新表名*/){  int iDb;                  /* Database that contains the table 包含表的数据库*/  char *zDb;                /* Name of database iDb 数据库iDb 的名称*/  Table *pTab;              /* Table being renamed 正在重命名的表*/  char *zName = 0;          /* NULL-terminated version of pName  pName的空值终止版本*/   sqlite3 *db = pParse->db; /* Database connection 数据库的连接*/  int nTabName;             /* Number of UTF-8 characters in zTabName 在 zTabName里的UTF-8类型的数目*/  const char *zTabName;     /* Original name of the table 最初的数据库名称*/  Vdbe *v;#ifndef SQLITE_OMIT_TRIGGER  char *zWhere = 0;         /* Where clause to locate temp triggers Where 子句位于temp触发器*/#endif  VTable *pVTab = 0;        /* Non-zero if this is a v-tab with an xRename() 如果是 一个v-tab 和一个xRename() ，则为零*/  int savedDbFlags;         /* Saved value of db->flags db->flags的保留值*/  savedDbFlags = db->flags;    if( NEVER(db->mallocFailed) ) goto exit_rename_table;  assert( pSrc->nSrc==1 );  assert( sqlite3BtreeHoldsAllMutexes(pParse->db) );  pTab = sqlite3LocateTable(pParse, 0, pSrc->a[0].zName, pSrc->a[0].zDatabase);  if( !pTab ) goto exit_rename_table;  iDb = sqlite3SchemaToIndex(pParse->db, pTab->pSchema);  zDb = db->aDb[iDb].zName;  db->flags |= SQLITE_PreferBuiltin;  /* Get a NULL terminated version of the new table name. 得到一个空终止版本的新表的名称。*/  zName = sqlite3NameFromToken(db, pName);  if( !zName ) goto exit_rename_table;  /* Check that a table or index named 'zName' does not already exist  ** in database iDb. If so, this is an error.检查一个表或索引名叫“zName”不存在数据库iDb。  如果是这样,这是一个错误。  */  if( sqlite3FindTable(db, zName, zDb) || sqlite3FindIndex(db, zName, zDb) ){    sqlite3ErrorMsg(pParse,         "there is already another table or index with this name: %s", zName);    goto exit_rename_table;  }  /* Make sure it is not a system table being altered, or a reserved name  ** that the table is being renamed to.  确保它不是一个正在被修改的系统表或者一个正在被重命名的保留的名称表  */  if( SQLITE_OK!=isSystemTable(pParse, pTab->zName) ){    goto exit_rename_table;  }  if( SQLITE_OK!=sqlite3CheckObjectName(pParse, zName) ){ goto    exit_rename_table;  }#ifndef SQLITE_OMIT_VIEW  if( pTab->pSelect ){    sqlite3ErrorMsg(pParse, "view %s may not be altered", pTab->zName);    goto exit_rename_table;  }#endif#ifndef SQLITE_OMIT_AUTHORIZATION  /* Invoke the authorization callback. 调用授权回调。*/  if( sqlite3AuthCheck(pParse, SQLITE_ALTER_TABLE, zDb, pTab->zName, 0) ){    goto exit_rename_table;  }#endif#ifndef SQLITE_OMIT_VIRTUALTABLE  if( sqlite3ViewGetColumnNames(pParse, pTab) ){    goto exit_rename_table;  }  if( IsVirtual(pTab) ){    pVTab = sqlite3GetVTable(db, pTab);    if( pVTab->pVtab->pModule->xRename==0 ){      pVTab = 0;    }  }#endif  /* Begin a transaction and code the VerifyCookie for database iDb.   ** Then modify the schema cookie (since the ALTER TABLE modifies the  ** schema). Open a statement transaction if the table is a virtual  ** table.  对于iDb数据库开始一个事务和代码的VerifyCookie。然后修改模式cookie(因为ALTER TABLE修改模式)。如果表是一个虚拟表打开一个声明事务。  */  v = sqlite3GetVdbe(pParse);  if( v==0 ){    goto exit_rename_table;  }  sqlite3BeginWriteOperation(pParse, pVTab!=0, iDb);  sqlite3ChangeCookie(pParse, iDb);//.........这里部分代码省略.........

/*** Generate code to implement the "ALTER TABLE xxx RENAME TO yyy" ** command. */void sqlite3AlterRenameTable(  Parse *pParse,            /* Parser context. */  SrcList *pSrc,            /* The table to rename. */  Token *pName              /* The new table name. */){  int iDb;                  /* Database that contains the table */  char *zDb;                /* Name of database iDb */  Table *pTab;              /* Table being renamed */  char *zName = 0;          /* NULL-terminated version of pName */   sqlite3 *db = pParse->db; /* Database connection */  Vdbe *v;#ifndef SQLITE_OMIT_TRIGGER  char *zWhere = 0;         /* Where clause to locate temp triggers */#endif    if( sqlite3_malloc_failed ) goto exit_rename_table;  assert( pSrc->nSrc==1 );  pTab = sqlite3LocateTable(pParse, pSrc->a[0].zName, pSrc->a[0].zDatabase);  if( !pTab ) goto exit_rename_table;  iDb = pTab->iDb;  zDb = db->aDb[iDb].zName;  /* Get a NULL terminated version of the new table name. */  zName = sqlite3NameFromToken(pName);  if( !zName ) goto exit_rename_table;  /* Check that a table or index named 'zName' does not already exist  ** in database iDb. If so, this is an error.  */  if( sqlite3FindTable(db, zName, zDb) || sqlite3FindIndex(db, zName, zDb) ){    sqlite3ErrorMsg(pParse,         "there is already another table or index with this name: %s", zName);    goto exit_rename_table;  }  /* Make sure it is not a system table being altered, or a reserved name  ** that the table is being renamed to.  */  if( strlen(pTab->zName)>6 && 0==sqlite3StrNICmp(pTab->zName, "sqlite_", 7) ){    sqlite3ErrorMsg(pParse, "table %s may not be altered", pTab->zName);    goto exit_rename_table;  }  if( SQLITE_OK!=sqlite3CheckObjectName(pParse, zName) ){    goto exit_rename_table;  }#ifndef SQLITE_OMIT_AUTHORIZATION  /* Invoke the authorization callback. */  if( sqlite3AuthCheck(pParse, SQLITE_ALTER_TABLE, zDb, pTab->zName, 0) ){    goto exit_rename_table;  }#endif  /* Begin a transaction and code the VerifyCookie for database iDb.   ** Then modify the schema cookie (since the ALTER TABLE modifies the  ** schema).  */  v = sqlite3GetVdbe(pParse);  if( v==0 ){    goto exit_rename_table;  }  sqlite3BeginWriteOperation(pParse, 0, iDb);  sqlite3ChangeCookie(db, v, iDb);  /* Modify the sqlite_master table to use the new table name. */  sqlite3NestedParse(pParse,      "UPDATE %Q.%s SET "#ifdef SQLITE_OMIT_TRIGGER          "sql = sqlite_rename_table(sql, %Q), "#else          "sql = CASE "            "WHEN type = 'trigger' THEN sqlite_rename_trigger(sql, %Q)"            "ELSE sqlite_rename_table(sql, %Q) END, "#endif          "tbl_name = %Q, "          "name = CASE "            "WHEN type='table' THEN %Q "            "WHEN name LIKE 'sqlite_autoindex%%' AND type='index' THEN "              "'sqlite_autoindex_' || %Q || substr(name, %d+18,10) "            "ELSE name END "      "WHERE tbl_name=%Q AND "          "(type='table' OR type='index' OR type='trigger');",       zDb, SCHEMA_TABLE(iDb), zName, zName, zName, #ifndef SQLITE_OMIT_TRIGGER      zName,#endif      zName, strlen(pTab->zName), pTab->zName  );#ifndef SQLITE_OMIT_AUTOINCREMENT  /* If the sqlite_sequence table exists in this database, then update   ** it with the new table name.  */  if( sqlite3FindTable(db, "sqlite_sequence", zDb) ){    sqlite3NestedParse(pParse,//.........这里部分代码省略.........

/*** Given the name of a column of the form X.Y.Z or Y.Z or just Z, look up** that name in the set of source tables in pSrcList and make the pExpr ** expression node refer back to that source column.  The following changes** are made to pExpr:****    pExpr->iDb           Set the index in db->aDb[] of the database X**                         (even if X is implied).**    pExpr->iTable        Set to the cursor number for the table obtained**                         from pSrcList.**    pExpr->pTab          Points to the Table structure of X.Y (even if**                         X and/or Y are implied.)**    pExpr->iColumn       Set to the column number within the table.**    pExpr->op            Set to TK_COLUMN.**    pExpr->pLeft         Any expression this points to is deleted**    pExpr->pRight        Any expression this points to is deleted.**** The pDbToken is the name of the database (the "X").  This value may be** NULL meaning that name is of the form Y.Z or Z.  Any available database** can be used.  The pTableToken is the name of the table (the "Y").  This** value can be NULL if pDbToken is also NULL.  If pTableToken is NULL it** means that the form of the name is Z and that columns from any table** can be used.**** If the name cannot be resolved unambiguously, leave an error message** in pParse and return non-zero.  Return zero on success.*/static int lookupName(  Parse *pParse,       /* The parsing context */  Token *pDbToken,     /* Name of the database containing table, or NULL */  Token *pTableToken,  /* Name of table containing column, or NULL */  Token *pColumnToken, /* Name of the column. */  NameContext *pNC,    /* The name context used to resolve the name */  Expr *pExpr          /* Make this EXPR node point to the selected column */){  char *zDb = 0;       /* Name of the database.  The "X" in X.Y.Z */  char *zTab = 0;      /* Name of the table.  The "Y" in X.Y.Z or Y.Z */  char *zCol = 0;      /* Name of the column.  The "Z" */  int i, j;            /* Loop counters */  int cnt = 0;                      /* Number of matching column names */  int cntTab = 0;                   /* Number of matching table names */  sqlite3 *db = pParse->db;         /* The database connection */  struct SrcList_item *pItem;       /* Use for looping over pSrcList items */  struct SrcList_item *pMatch = 0;  /* The matching pSrcList item */  NameContext *pTopNC = pNC;        /* First namecontext in the list */  Schema *pSchema = 0;              /* Schema of the expression */  assert( pColumnToken && pColumnToken->z ); /* The Z in X.Y.Z cannot be NULL */  /* Dequote and zero-terminate the names */  zDb = sqlite3NameFromToken(db, pDbToken);  zTab = sqlite3NameFromToken(db, pTableToken);  zCol = sqlite3NameFromToken(db, pColumnToken);  if( db->mallocFailed ){    goto lookupname_end;  }  /* Initialize the node to no-match */  pExpr->iTable = -1;  pExpr->pTab = 0;  /* Start at the inner-most context and move outward until a match is found */  while( pNC && cnt==0 ){    ExprList *pEList;    SrcList *pSrcList = pNC->pSrcList;    if( pSrcList ){      for(i=0, pItem=pSrcList->a; i<pSrcList->nSrc; i++, pItem++){        Table *pTab;        int iDb;        Column *pCol;          pTab = pItem->pTab;        assert( pTab!=0 && pTab->zName!=0 );        iDb = sqlite3SchemaToIndex(db, pTab->pSchema);        assert( pTab->nCol>0 );        if( zTab ){          if( pItem->zAlias ){            char *zTabName = pItem->zAlias;            if( sqlite3StrICmp(zTabName, zTab)!=0 ) continue;          }else{            char *zTabName = pTab->zName;            if( zTabName==0 || sqlite3StrICmp(zTabName, zTab)!=0 ) continue;            if( zDb!=0 && sqlite3StrICmp(db->aDb[iDb].zName, zDb)!=0 ){              continue;            }          }        }        if( 0==(cntTab++) ){          pExpr->iTable = pItem->iCursor;          pExpr->pTab = pTab;          pSchema = pTab->pSchema;          pMatch = pItem;        }        for(j=0, pCol=pTab->aCol; j<pTab->nCol; j++, pCol++){          if( sqlite3StrICmp(pCol->zName, zCol)==0 ){            IdList *pUsing;            cnt++;            pExpr->iTable = pItem->iCursor;            pExpr->pTab = pTab;//.........这里部分代码省略.........

/*** This routine is called by the parser to process an ATTACH statement:****     ATTACH DATABASE filename AS dbname**** The pFilename and pDbname arguments are the tokens that define the** filename and dbname in the ATTACH statement.*/void sqlite3Attach(  Parse *pParse,       /* The parser context */  Token *pFilename,    /* Name of database file */  Token *pDbname,      /* Name of the database to use internally */  int keyType,         /* 0: no key.  1: TEXT,  2: BLOB */  Token *pKey          /* Text of the key for keytype 1 and 2 */){  Db *aNew;  int rc, i;  char *zFile, *zName;  sqlite3 *db;  Vdbe *v;  v = sqlite3GetVdbe(pParse);  if( !v ) return;  sqlite3VdbeAddOp(v, OP_Halt, 0, 0);  if( pParse->explain ) return;  db = pParse->db;  if( db->nDb>=MAX_ATTACHED+2 ){    sqlite3ErrorMsg(pParse, "too many attached databases - max %d",        MAX_ATTACHED);    pParse->rc = SQLITE_ERROR;    return;  }  if( !db->autoCommit ){    sqlite3ErrorMsg(pParse, "cannot ATTACH database within transaction");    pParse->rc = SQLITE_ERROR;    return;  }  zFile = sqlite3NameFromToken(pFilename);;  if( zFile==0 ) return;#ifndef SQLITE_OMIT_AUTHORIZATION  if( sqlite3AuthCheck(pParse, SQLITE_ATTACH, zFile, 0, 0)!=SQLITE_OK ){    sqliteFree(zFile);    return;  }#endif /* SQLITE_OMIT_AUTHORIZATION */  zName = sqlite3NameFromToken(pDbname);  if( zName==0 ) return;  for(i=0; i<db->nDb; i++){    char *z = db->aDb[i].zName;    if( z && sqlite3StrICmp(z, zName)==0 ){      sqlite3ErrorMsg(pParse, "database %z is already in use", zName);      pParse->rc = SQLITE_ERROR;      sqliteFree(zFile);      return;    }  }  if( db->aDb==db->aDbStatic ){    aNew = sqliteMalloc( sizeof(db->aDb[0])*3 );    if( aNew==0 ) return;    memcpy(aNew, db->aDb, sizeof(db->aDb[0])*2);  }else{    aNew = sqliteRealloc(db->aDb, sizeof(db->aDb[0])*(db->nDb+1) );    if( aNew==0 ) return;  }  db->aDb = aNew;  aNew = &db->aDb[db->nDb++];  memset(aNew, 0, sizeof(*aNew));  sqlite3HashInit(&aNew->tblHash, SQLITE_HASH_STRING, 0);  sqlite3HashInit(&aNew->idxHash, SQLITE_HASH_STRING, 0);  sqlite3HashInit(&aNew->trigHash, SQLITE_HASH_STRING, 0);  sqlite3HashInit(&aNew->aFKey, SQLITE_HASH_STRING, 1);  aNew->zName = zName;  aNew->safety_level = 3;  rc = sqlite3BtreeFactory(db, zFile, 0, MAX_PAGES, &aNew->pBt);  if( rc ){    sqlite3ErrorMsg(pParse, "unable to open database: %s", zFile);  }#if SQLITE_HAS_CODEC  {    extern int sqlite3CodecAttach(sqlite3*, int, void*, int);    char *zKey;    int nKey;    if( keyType==0 ){      /* No key specified.  Use the key from the main database */      extern void sqlite3CodecGetKey(sqlite3*, int, void**, int*);      sqlite3CodecGetKey(db, 0, (void**)&zKey, &nKey);    }else if( keyType==1 ){      /* Key specified as text */      zKey = sqlite3NameFromToken(pKey);      nKey = strlen(zKey);    }else{      /* Key specified as a BLOB */      char *zTemp;      assert( keyType==2 );      pKey->z++;      pKey->n--;//.........这里部分代码省略.........

/*** This is called by the parser when it sees a CREATE TRIGGER statement** up to the point of the BEGIN before the trigger actions.  A Trigger** structure is generated based on the information available and stored** in pParse->pNewTrigger.  After the trigger actions have been parsed, the** sqlite3FinishTrigger() function is called to complete the trigger** construction process.*/void sqlite3BeginTrigger(  Parse *pParse,      /* The parse context of the CREATE TRIGGER statement */  Token *pName1,      /* The name of the trigger */  Token *pName2,      /* The name of the trigger */  int tr_tm,          /* One of TK_BEFORE, TK_AFTER, TK_INSTEAD */  int op,             /* One of TK_INSERT, TK_UPDATE, TK_DELETE */  IdList *pColumns,   /* column list if this is an UPDATE OF trigger */  SrcList *pTableName,/* The name of the table/view the trigger applies to */  int foreach,        /* One of TK_ROW or TK_STATEMENT */  Expr *pWhen,        /* WHEN clause */  int isTemp          /* True if the TEMPORARY keyword is present */){  Trigger *pTrigger;  Table *pTab;  char *zName = 0;        /* Name of the trigger */  sqlite *db = pParse->db;  int iDb;                /* The database to store the trigger in */  Token *pName;           /* The unqualified db name */  DbFixer sFix;  if( isTemp ){    /* If TEMP was specified, then the trigger name may not be qualified. */    if( pName2 && pName2->n>0 ){      sqlite3ErrorMsg(pParse, "temporary trigger may not have qualified name");      goto trigger_cleanup;    }    iDb = 1;    pName = pName1;  }else{    /* Figure out the db that the the trigger will be created in */    iDb = sqlite3TwoPartName(pParse, pName1, pName2, &pName);    if( iDb<0 ){      goto trigger_cleanup;    }  }  /* If the trigger name was unqualified, and the table is a temp table,  ** then set iDb to 1 to create the trigger in the temporary database.  ** If sqlite3SrcListLookup() returns 0, indicating the table does not  ** exist, the error is caught by the block below.  */  if( !pTableName || sqlite3_malloc_failed ) goto trigger_cleanup;  pTab = sqlite3SrcListLookup(pParse, pTableName);  if( pName2->n==0 && pTab && pTab->iDb==1 ){    iDb = 1;  }  /* Ensure the table name matches database name and that the table exists */  if( sqlite3_malloc_failed ) goto trigger_cleanup;  assert( pTableName->nSrc==1 );  if( sqlite3FixInit(&sFix, pParse, iDb, "trigger", pName) &&       sqlite3FixSrcList(&sFix, pTableName) ){    goto trigger_cleanup;  }  pTab = sqlite3SrcListLookup(pParse, pTableName);  if( !pTab ){    /* The table does not exist. */    goto trigger_cleanup;  }  /* Check that the trigger name is not reserved and that no trigger of the  ** specified name exists */  zName = sqlite3NameFromToken(pName);  if( !zName || SQLITE_OK!=sqlite3CheckObjectName(pParse, zName) ){    goto trigger_cleanup;  }  if( sqlite3HashFind(&(db->aDb[iDb].trigHash), zName,pName->n+1) ){    sqlite3ErrorMsg(pParse, "trigger %T already exists", pName);    goto trigger_cleanup;  }  /* Do not create a trigger on a system table */  if( (iDb!=1 && sqlite3StrICmp(pTab->zName, MASTER_NAME)==0) ||       (iDb==1 && sqlite3StrICmp(pTab->zName, TEMP_MASTER_NAME)==0)   ){    sqlite3ErrorMsg(pParse, "cannot create trigger on system table");    pParse->nErr++;    goto trigger_cleanup;  }  /* INSTEAD of triggers are only for views and views only support INSTEAD  ** of triggers.  */  if( pTab->pSelect && tr_tm!=TK_INSTEAD ){    sqlite3ErrorMsg(pParse, "cannot create %s trigger on view: %S",         (tr_tm == TK_BEFORE)?"BEFORE":"AFTER", pTableName, 0);    goto trigger_cleanup;  }  if( !pTab->pSelect && tr_tm==TK_INSTEAD ){    sqlite3ErrorMsg(pParse, "cannot create INSTEAD OF"        " trigger on table: %S", pTableName, 0);    goto trigger_cleanup;//.........这里部分代码省略.........

/*** Process a pragma statement.  **** Pragmas are of this form:****      PRAGMA [database.]id [= value]**** The identifier might also be a string.  The value is a string, and** identifier, or a number.  If minusFlag is true, then the value is** a number that was preceded by a minus sign.**** If the left side is "database.id" then pId1 is the database name** and pId2 is the id.  If the left side is just "id" then pId1 is the** id and pId2 is any empty string.*/void sqlite3Pragma(  Parse *pParse,   Token *pId1,        /* First part of [database.]id field */  Token *pId2,        /* Second part of [database.]id field, or NULL */  Token *pValue,      /* Token for <value>, or NULL */  int minusFlag       /* True if a '-' sign preceded <value> */){  char *zLeft = 0;       /* Nul-terminated UTF-8 string <id> */  char *zRight = 0;      /* Nul-terminated UTF-8 string <value>, or NULL */  const char *zDb = 0;   /* The database name */  Token *pId;            /* Pointer to <id> token */  int iDb;               /* Database index for <database> */  sqlite3 *db = pParse->db;  Db *pDb;  Vdbe *v = pParse->pVdbe = sqlite3VdbeCreate(db);  if( v==0 ) return;  pParse->nMem = 2;  /* Interpret the [database.] part of the pragma statement. iDb is the  ** index of the database this pragma is being applied to in db.aDb[]. */  iDb = sqlite3TwoPartName(pParse, pId1, pId2, &pId);  if( iDb<0 ) return;  pDb = &db->aDb[iDb];  /* If the temp database has been explicitly named as part of the   ** pragma, make sure it is open.   */  if( iDb==1 && sqlite3OpenTempDatabase(pParse) ){    return;  }  zLeft = sqlite3NameFromToken(db, pId);  if( !zLeft ) return;  if( minusFlag ){    zRight = sqlite3MPrintf(db, "-%T", pValue);  }else{    zRight = sqlite3NameFromToken(db, pValue);  }  zDb = ((pId2 && pId2->n>0)?pDb->zName:0);  if( sqlite3AuthCheck(pParse, SQLITE_PRAGMA, zLeft, zRight, zDb) ){    goto pragma_out;  } #ifndef SQLITE_OMIT_PAGER_PRAGMAS  /*  **  PRAGMA [database.]default_cache_size  **  PRAGMA [database.]default_cache_size=N  **  ** The first form reports the current persistent setting for the  ** page cache size.  The value returned is the maximum number of  ** pages in the page cache.  The second form sets both the current  ** page cache size value and the persistent page cache size value  ** stored in the database file.  **  ** The default cache size is stored in meta-value 2 of page 1 of the  ** database file.  The cache size is actually the absolute value of  ** this memory location.  The sign of meta-value 2 determines the  ** synchronous setting.  A negative value means synchronous is off  ** and a positive value means synchronous is on.  */  if( sqlite3StrICmp(zLeft,"default_cache_size")==0 ){    static const VdbeOpList getCacheSize[] = {      { OP_ReadCookie,  0, 1,        2},  /* 0 */      { OP_IfPos,       1, 6,        0},      { OP_Integer,     0, 2,        0},      { OP_Subtract,    1, 2,        1},      { OP_IfPos,       1, 6,        0},      { OP_Integer,     0, 1,        0},  /* 5 */      { OP_ResultRow,   1, 1,        0},    };    int addr;    if( sqlite3ReadSchema(pParse) ) goto pragma_out;    sqlite3VdbeUsesBtree(v, iDb);    if( !zRight ){      sqlite3VdbeSetNumCols(v, 1);      sqlite3VdbeSetColName(v, 0, COLNAME_NAME, "cache_size", P4_STATIC);      pParse->nMem += 2;      addr = sqlite3VdbeAddOpList(v, ArraySize(getCacheSize), getCacheSize);      sqlite3VdbeChangeP1(v, addr, iDb);      sqlite3VdbeChangeP1(v, addr+5, SQLITE_DEFAULT_CACHE_SIZE);    }else{      int size = atoi(zRight);      if( size<0 ) size = -size;      sqlite3BeginWriteOperation(pParse, 0, iDb);//.........这里部分代码省略.........