vtab.c

sqlite-3.4.1,嵌入式数据库.是一个功能强大的开源数据库,给学习和研发以及小型公司的发展带来了全所未有的好处.

/*
** 2006 June 10
**
** 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 used to help implement virtual tables.
**
** $Id: vtab.c,v 1.48 2007/06/26 10:38:55 danielk1977 Exp $
*/
#ifndef SQLITE_OMIT_VIRTUALTABLE
#include "sqliteInt.h"

static int createModule(
  sqlite3 *db,                    /* Database in which module is registered */
  const char *zName,              /* Name assigned to this module */
  const sqlite3_module *pModule,  /* The definition of the module */
  void *pAux,                     /* Context pointer for xCreate/xConnect */
  void (*xDestroy)(void *)        /* Module destructor function */
) {
  int nName = strlen(zName);
  Module *pMod = (Module *)sqliteMallocRaw(sizeof(Module) + nName + 1);
  if( pMod ){
    char *zCopy = (char *)(&pMod[1]);
    memcpy(zCopy, zName, nName+1);
    pMod->zName = zCopy;
    pMod->pModule = pModule;
    pMod->pAux = pAux;
    pMod->xDestroy = xDestroy;
    pMod = (Module *)sqlite3HashInsert(&db->aModule, zCopy, nName, (void*)pMod);
    if( pMod && pMod->xDestroy ){
      pMod->xDestroy(pMod->pAux);
    }
    sqliteFree(pMod);
    sqlite3ResetInternalSchema(db, 0);
  }
  return sqlite3ApiExit(db, SQLITE_OK);
}


/*
** External API function used to create a new virtual-table module.
*/
int sqlite3_create_module(
  sqlite3 *db,                    /* Database in which module is registered */
  const char *zName,              /* Name assigned to this module */
  const sqlite3_module *pModule,  /* The definition of the module */
  void *pAux                      /* Context pointer for xCreate/xConnect */
){
  return createModule(db, zName, pModule, pAux, 0);
}

/*
** External API function used to create a new virtual-table module.
*/
int sqlite3_create_module_v2(
  sqlite3 *db,                    /* Database in which module is registered */
  const char *zName,              /* Name assigned to this module */
  const sqlite3_module *pModule,  /* The definition of the module */
  void *pAux,                     /* Context pointer for xCreate/xConnect */
  void (*xDestroy)(void *)        /* Module destructor function */
){
  return createModule(db, zName, pModule, pAux, xDestroy);
}

/*
** Lock the virtual table so that it cannot be disconnected.
** Locks nest.  Every lock should have a corresponding unlock.
** If an unlock is omitted, resources leaks will occur.  
**
** If a disconnect is attempted while a virtual table is locked,
** the disconnect is deferred until all locks have been removed.
*/
void sqlite3VtabLock(sqlite3_vtab *pVtab){
  pVtab->nRef++;
}

/*
** Unlock a virtual table.  When the last lock is removed,
** disconnect the virtual table.
*/
void sqlite3VtabUnlock(sqlite3 *db, sqlite3_vtab *pVtab){
  pVtab->nRef--;
  assert(db);
  assert(!sqlite3SafetyCheck(db));
  if( pVtab->nRef==0 ){
    if( db->magic==SQLITE_MAGIC_BUSY ){
      sqlite3SafetyOff(db);
      pVtab->pModule->xDisconnect(pVtab);
      sqlite3SafetyOn(db);
    } else {
      pVtab->pModule->xDisconnect(pVtab);
    }
  }
}

/*
** Clear any and all virtual-table information from the Table record.
** This routine is called, for example, just before deleting the Table
** record.
*/
void sqlite3VtabClear(Table *p){
  sqlite3_vtab *pVtab = p->pVtab;
  if( pVtab ){
    assert( p->pMod && p->pMod->pModule );
    sqlite3VtabUnlock(p->pSchema->db, pVtab);
    p->pVtab = 0;
  }
  if( p->azModuleArg ){
    int i;
    for(i=0; i<p->nModuleArg; i++){
      sqliteFree(p->azModuleArg[i]);
    }
    sqliteFree(p->azModuleArg);
  }
}

/*
** Add a new module argument to pTable->azModuleArg[].
** The string is not copied - the pointer is stored.  The
** string will be freed automatically when the table is
** deleted.
*/
static void addModuleArgument(Table *pTable, char *zArg){
  int i = pTable->nModuleArg++;
  int nBytes = sizeof(char *)*(1+pTable->nModuleArg);
  char **azModuleArg;
  azModuleArg = sqliteRealloc(pTable->azModuleArg, nBytes);
  if( azModuleArg==0 ){
    int j;
    for(j=0; j<i; j++){
      sqliteFree(pTable->azModuleArg[j]);
    }
    sqliteFree(zArg);
    sqliteFree(pTable->azModuleArg);
    pTable->nModuleArg = 0;
  }else{
    azModuleArg[i] = zArg;
    azModuleArg[i+1] = 0;
  }
  pTable->azModuleArg = azModuleArg;
}

/*
** 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 takes the module argument that has been accumulating
** in pParse->zArg[] and appends it to the list of arguments on the
** virtual table currently under construction in pParse->pTable.
*/
static void addArgumentToVtab(Parse *pParse){
  if( pParse->sArg.z && pParse->pNewTable ){
    const char *z = (const char*)pParse->sArg.z;
    int n = pParse->sArg.n;
    addModuleArgument(pParse->pNewTable, sqliteStrNDup(z, n));
  }
}

/*
** The parser calls this routine after the CREATE VIRTUAL TABLE statement
** has been completely parsed.
*/
void sqlite3VtabFinishParse(Parse *pParse, Token *pEnd){
  Table *pTab;        /* The table being constructed */
  sqlite3 *db;        /* The database connection */
  char *zModule;      /* The module name of the table: USING modulename */
  Module *pMod = 0;

  addArgumentToVtab(pParse);
  pParse->sArg.z = 0;

  /* Lookup the module name. */
  pTab = pParse->pNewTable;
  if( pTab==0 ) return;
  db = pParse->db;
  if( pTab->nModuleArg<1 ) return;
  zModule = pTab->azModuleArg[0];
  pMod = (Module *)sqlite3HashFind(&db->aModule, zModule, strlen(zModule));
  pTab->pMod = pMod;
  
  /* If the CREATE VIRTUAL TABLE statement is being entered for the
  ** first time (in other words if the virtual table is actually being
  ** created now instead of just being read out of sqlite_master) then
  ** do additional initialization work and store the statement text
  ** in the sqlite_master table.
  */
  if( !db->init.busy ){
    char *zStmt;
    char *zWhere;
    int iDb;
    Vdbe *v;

    /* Compute the complete text of the CREATE VIRTUAL TABLE statement */
    if( pEnd ){
      pParse->sNameToken.n = pEnd->z - pParse->sNameToken.z + pEnd->n;
    }
    zStmt = sqlite3MPrintf("CREATE VIRTUAL TABLE %T", &pParse->sNameToken);

    /* A slot for the record has already been allocated in the 
    ** SQLITE_MASTER table.  We just need to update that slot with all
    ** the information we've collected.  
    **
    ** The top of the stack is the rootpage allocated by sqlite3StartTable().
    ** This value is always 0 and is ignored, a virtual table does not have a
    ** rootpage. The next entry on the stack is the rowid of the record
    ** in the sqlite_master table.
    */
    iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
    sqlite3NestedParse(pParse,
      "UPDATE %Q.%s "
         "SET type='table', name=%Q, tbl_name=%Q, rootpage=0, sql=%Q "
       "WHERE rowid=#1",
      db->aDb[iDb].zName, SCHEMA_TABLE(iDb),
      pTab->zName,
      pTab->zName,
      zStmt
    );
    sqliteFree(zStmt);
    v = sqlite3GetVdbe(pParse);
    sqlite3ChangeCookie(db, v, iDb);

    sqlite3VdbeAddOp(v, OP_Expire, 0, 0);
    zWhere = sqlite3MPrintf("name='%q'", pTab->zName);
    sqlite3VdbeOp3(v, OP_ParseSchema, iDb, 1, zWhere, P3_DYNAMIC);
    sqlite3VdbeOp3(v, OP_VCreate, iDb, 0, pTab->zName, strlen(pTab->zName) + 1);
  }

  /* If we are rereading the sqlite_master table create the in-memory
  ** record of the table. If the module has already been registered,
  ** also call the xConnect method here.
  */
  else {
    Table *pOld;
    Schema *pSchema = pTab->pSchema;
    const char *zName = pTab->zName;
    int nName = strlen(zName) + 1;
    pOld = sqlite3HashInsert(&pSchema->tblHash, zName, nName, pTab);
    if( pOld ){
      assert( pTab==pOld );  /* Malloc must have failed inside HashInsert() */
      return;
    }
    pSchema->db = pParse->db;
    pParse->pNewTable = 0;
  }
}

/*
** The parser calls this routine when it sees the first token
** of an argument to the module name in a CREATE VIRTUAL TABLE statement.
*/
void sqlite3VtabArgInit(Parse *pParse){
  addArgumentToVtab(pParse);
  pParse->sArg.z = 0;
  pParse->sArg.n = 0;
}

/*
** The parser calls this routine for each token after the first token
** in an argument to the module name in a CREATE VIRTUAL TABLE statement.
*/
void sqlite3VtabArgExtend(Parse *pParse, Token *p){
  Token *pArg = &pParse->sArg;
  if( pArg->z==0 ){
    pArg->z = p->z;
    pArg->n = p->n;
  }else{
    assert(pArg->z < p->z);
    pArg->n = (p->z + p->n - pArg->z);
  }
}

/*
** Invoke a virtual table constructor (either xCreate or xConnect). The
** pointer to the function to invoke is passed as the fourth parameter
** to this procedure.
*/
static int vtabCallConstructor(
  sqlite3 *db, 
  Table *pTab,
  Module *pMod,
  int (*xConstruct)(sqlite3*,void*,int,const char*const*,sqlite3_vtab**,char**),
  char **pzErr
){
  int rc;
  int rc2;
  sqlite3_vtab *pVtab;
  const char *const*azArg = (const char *const*)pTab->azModuleArg;
  int nArg = pTab->nModuleArg;
  char *zErr = 0;
  char *zModuleName = sqlite3MPrintf("%s", pTab->zName);

  if( !zModuleName ){
    return SQLITE_NOMEM;
  }

  assert( !db->pVTab );
  assert( xConstruct );

  db->pVTab = pTab;
  rc = sqlite3SafetyOff(db);
  assert( rc==SQLITE_OK );
  rc = xConstruct(db, pMod->pAux, nArg, azArg, &pTab->pVtab, &zErr);
  rc2 = sqlite3SafetyOn(db);
  pVtab = pTab->pVtab;
  if( rc==SQLITE_OK && pVtab ){
    pVtab->pModule = pMod->pModule;
    pVtab->nRef = 1;
  }

  if( SQLITE_OK!=rc ){
    if( zErr==0 ){
      *pzErr = sqlite3MPrintf("vtable constructor failed: %s", zModuleName);
    }else {
      *pzErr = sqlite3MPrintf("%s", zErr);
      sqlite3_free(zErr);
    }
  }else if( db->pVTab ){
    const char *zFormat = "vtable constructor did not declare schema: %s";
    *pzErr = sqlite3MPrintf(zFormat, pTab->zName);
    rc = SQLITE_ERROR;
  } 
  if( rc==SQLITE_OK ){
    rc = rc2;
  }
  db->pVTab = 0;
  sqliteFree(zModuleName);

  /* If everything went according to plan, loop through the columns
  ** of the table to see if any of them contain the token "hidden".
  ** If so, set the Column.isHidden flag and remove the token from
  ** the type string.
  */
  if( rc==SQLITE_OK ){
    int iCol;
    for(iCol=0; iCol<pTab->nCol; iCol++){
      char *zType = pTab->aCol[iCol].zType;
      int nType;
      int i = 0;
      if( !zType ) continue;