trigger.c

sqlite数据库管理系统开放源码

 * removes it from the internal schema and places it in the trigDrop hash 
 * table. This is so that the trigger can be restored into the database schema
 * if the transaction is rolled back.
 */
void sqliteDropTrigger(Parse *pParse, SrcList *pName){
  Trigger *pTrigger;
  int i;
  const char *zDb;
  const char *zName;
  int nName;
  sqlite *db = pParse->db;

  if( sqlite_malloc_failed ) goto drop_trigger_cleanup;
  assert( pName->nSrc==1 );
  zDb = pName->a[0].zDatabase;
  zName = pName->a[0].zName;
  nName = strlen(zName);
  for(i=0; i<db->nDb; i++){
    int j = (i<2) ? i^1 : i;  /* Search TEMP before MAIN */
    if( zDb && sqliteStrICmp(db->aDb[j].zName, zDb) ) continue;
    pTrigger = sqliteHashFind(&(db->aDb[j].trigHash), zName, nName+1);
    if( pTrigger ) break;
  }
  if( !pTrigger ){
    sqliteErrorMsg(pParse, "no such trigger: %S", pName, 0);
    goto drop_trigger_cleanup;
  }
  sqliteDropTriggerPtr(pParse, pTrigger, 0);

drop_trigger_cleanup:
  sqliteSrcListDelete(pName);
}

/*
** Drop a trigger given a pointer to that trigger.  If nested is false,
** then also generate code to remove the trigger from the SQLITE_MASTER
** table.
*/
void sqliteDropTriggerPtr(Parse *pParse, Trigger *pTrigger, int nested){
  Table   *pTable;
  Vdbe *v;
  sqlite *db = pParse->db;

  assert( pTrigger->iDb<db->nDb );
  if( pTrigger->iDb>=2 ){
    sqliteErrorMsg(pParse, "triggers may not be removed from "
       "auxiliary database %s", db->aDb[pTrigger->iDb].zName);
    return;
  }
  pTable = sqliteFindTable(db, pTrigger->table,db->aDb[pTrigger->iTabDb].zName);
  assert(pTable);
  assert( pTable->iDb==pTrigger->iDb || pTrigger->iDb==1 );
#ifndef SQLITE_OMIT_AUTHORIZATION
  {
    int code = SQLITE_DROP_TRIGGER;
    const char *zDb = db->aDb[pTrigger->iDb].zName;
    const char *zTab = SCHEMA_TABLE(pTrigger->iDb);
    if( pTrigger->iDb ) code = SQLITE_DROP_TEMP_TRIGGER;
    if( sqliteAuthCheck(pParse, code, pTrigger->name, pTable->zName, zDb) ||
      sqliteAuthCheck(pParse, SQLITE_DELETE, zTab, 0, zDb) ){
      return;
    }
  }
#endif

  /* Generate code to destroy the database record of the trigger.
  */
  if( pTable!=0 && !nested && (v = sqliteGetVdbe(pParse))!=0 ){
    int base;
    static VdbeOpList dropTrigger[] = {
      { OP_Rewind,     0, ADDR(9),  0},
      { OP_String,     0, 0,        0}, /* 1 */
      { OP_Column,     0, 1,        0},
      { OP_Ne,         0, ADDR(8),  0},
      { OP_String,     0, 0,        "trigger"},
      { OP_Column,     0, 0,        0},
      { OP_Ne,         0, ADDR(8),  0},
      { OP_Delete,     0, 0,        0},
      { OP_Next,       0, ADDR(1),  0}, /* 8 */
    };

    sqliteBeginWriteOperation(pParse, 0, 0);
    sqliteOpenMasterTable(v, pTrigger->iDb);
    base = sqliteVdbeAddOpList(v,  ArraySize(dropTrigger), dropTrigger);
    sqliteVdbeChangeP3(v, base+1, pTrigger->name, 0);
    if( pTrigger->iDb==0 ){
      sqliteChangeCookie(db, v);
    }
    sqliteVdbeAddOp(v, OP_Close, 0, 0);
    sqliteEndWriteOperation(pParse);
  }

  /*
   * If this is not an "explain", then delete the trigger structure.
   */
  if( !pParse->explain ){
    const char *zName = pTrigger->name;
    int nName = strlen(zName);
    if( pTable->pTrigger == pTrigger ){
      pTable->pTrigger = pTrigger->pNext;
    }else{
      Trigger *cc = pTable->pTrigger;
      while( cc ){ 
        if( cc->pNext == pTrigger ){
          cc->pNext = cc->pNext->pNext;
          break;
        }
        cc = cc->pNext;
      }
      assert(cc);
    }
    sqliteHashInsert(&(db->aDb[pTrigger->iDb].trigHash), zName, nName+1, 0);
    sqliteDeleteTrigger(pTrigger);
  }
}

/*
** pEList is the SET clause of an UPDATE statement.  Each entry
** in pEList is of the format <id>=<expr>.  If any of the entries
** in pEList have an <id> which matches an identifier in pIdList,
** then return TRUE.  If pIdList==NULL, then it is considered a
** wildcard that matches anything.  Likewise if pEList==NULL then
** it matches anything so always return true.  Return false only
** if there is no match.
*/
static int checkColumnOverLap(IdList *pIdList, ExprList *pEList){
  int e;
  if( !pIdList || !pEList ) return 1;
  for(e=0; e<pEList->nExpr; e++){
    if( sqliteIdListIndex(pIdList, pEList->a[e].zName)>=0 ) return 1;
  }
  return 0; 
}

/* A global variable that is TRUE if we should always set up temp tables for
 * for triggers, even if there are no triggers to code. This is used to test 
 * how much overhead the triggers algorithm is causing.
 *
 * This flag can be set or cleared using the "trigger_overhead_test" pragma.
 * The pragma is not documented since it is not really part of the interface
 * to SQLite, just the test procedure.
*/
int always_code_trigger_setup = 0;

/*
 * Returns true if a trigger matching op, tr_tm and foreach that is NOT already
 * on the Parse objects trigger-stack (to prevent recursive trigger firing) is
 * found in the list specified as pTrigger.
 */
int sqliteTriggersExist(
  Parse *pParse,          /* Used to check for recursive triggers */
  Trigger *pTrigger,      /* A list of triggers associated with a table */
  int op,                 /* one of TK_DELETE, TK_INSERT, TK_UPDATE */
  int tr_tm,              /* one of TK_BEFORE, TK_AFTER */
  int foreach,            /* one of TK_ROW or TK_STATEMENT */
  ExprList *pChanges      /* Columns that change in an UPDATE statement */
){
  Trigger * pTriggerCursor;

  if( always_code_trigger_setup ){
    return 1;
  }

  pTriggerCursor = pTrigger;
  while( pTriggerCursor ){
    if( pTriggerCursor->op == op && 
	pTriggerCursor->tr_tm == tr_tm && 
	pTriggerCursor->foreach == foreach &&
	checkColumnOverLap(pTriggerCursor->pColumns, pChanges) ){
      TriggerStack * ss;
      ss = pParse->trigStack;
      while( ss && ss->pTrigger != pTrigger ){
	ss = ss->pNext;
      }
      if( !ss )return 1;
    }
    pTriggerCursor = pTriggerCursor->pNext;
  }

  return 0;
}

/*
** Convert the pStep->target token into a SrcList and return a pointer
** to that SrcList.
**
** This routine adds a specific database name, if needed, to the target when
** forming the SrcList.  This prevents a trigger in one database from
** referring to a target in another database.  An exception is when the
** trigger is in TEMP in which case it can refer to any other database it
** wants.
*/
static SrcList *targetSrcList(
  Parse *pParse,       /* The parsing context */
  TriggerStep *pStep   /* The trigger containing the target token */
){
  Token sDb;           /* Dummy database name token */
  int iDb;             /* Index of the database to use */
  SrcList *pSrc;       /* SrcList to be returned */

  iDb = pStep->pTrig->iDb;
  if( iDb==0 || iDb>=2 ){
    assert( iDb<pParse->db->nDb );
    sDb.z = pParse->db->aDb[iDb].zName;
    sDb.n = strlen(sDb.z);
    pSrc = sqliteSrcListAppend(0, &sDb, &pStep->target);
  } else {
    pSrc = sqliteSrcListAppend(0, &pStep->target, 0);
  }
  return pSrc;
}

/*
** Generate VDBE code for zero or more statements inside the body of a
** trigger.  
*/
static int codeTriggerProgram(
  Parse *pParse,            /* The parser context */
  TriggerStep *pStepList,   /* List of statements inside the trigger body */
  int orconfin              /* Conflict algorithm. (OE_Abort, etc) */  
){
  TriggerStep * pTriggerStep = pStepList;
  int orconf;

  while( pTriggerStep ){
    int saveNTab = pParse->nTab;
 
    orconf = (orconfin == OE_Default)?pTriggerStep->orconf:orconfin;
    pParse->trigStack->orconf = orconf;
    switch( pTriggerStep->op ){
      case TK_SELECT: {
	Select * ss = sqliteSelectDup(pTriggerStep->pSelect);		  
	assert(ss);
	assert(ss->pSrc);
	sqliteSelect(pParse, ss, SRT_Discard, 0, 0, 0, 0);
	sqliteSelectDelete(ss);
	break;
      }
      case TK_UPDATE: {
        SrcList *pSrc;
        pSrc = targetSrcList(pParse, pTriggerStep);
        sqliteVdbeAddOp(pParse->pVdbe, OP_ListPush, 0, 0);
        sqliteUpdate(pParse, pSrc,
		sqliteExprListDup(pTriggerStep->pExprList), 
		sqliteExprDup(pTriggerStep->pWhere), orconf);
        sqliteVdbeAddOp(pParse->pVdbe, OP_ListPop, 0, 0);
        break;
      }
      case TK_INSERT: {
        SrcList *pSrc;
        pSrc = targetSrcList(pParse, pTriggerStep);
        sqliteInsert(pParse, pSrc,
          sqliteExprListDup(pTriggerStep->pExprList), 
          sqliteSelectDup(pTriggerStep->pSelect), 
          sqliteIdListDup(pTriggerStep->pIdList), orconf);
        break;
      }
      case TK_DELETE: {
        SrcList *pSrc;
        sqliteVdbeAddOp(pParse->pVdbe, OP_ListPush, 0, 0);
        pSrc = targetSrcList(pParse, pTriggerStep);
        sqliteDeleteFrom(pParse, pSrc, sqliteExprDup(pTriggerStep->pWhere));
        sqliteVdbeAddOp(pParse->pVdbe, OP_ListPop, 0, 0);
        break;
      }
      default:
        assert(0);
    } 
    pParse->nTab = saveNTab;
    pTriggerStep = pTriggerStep->pNext;
  }

  return 0;
}

/*
** This is called to code FOR EACH ROW triggers.
**
** When the code that this function generates is executed, the following 
** must be true:
**
** 1. No cursors may be open in the main database.  (But newIdx and oldIdx
**    can be indices of cursors in temporary tables.  See below.)
**
** 2. If the triggers being coded are ON INSERT or ON UPDATE triggers, then
**    a temporary vdbe cursor (index newIdx) must be open and pointing at
**    a row containing values to be substituted for new.* expressions in the
**    trigger program(s).
**
** 3. If the triggers being coded are ON DELETE or ON UPDATE triggers, then
**    a temporary vdbe cursor (index oldIdx) must be open and pointing at
**    a row containing values to be substituted for old.* expressions in the
**    trigger program(s).
**
*/
int sqliteCodeRowTrigger(
  Parse *pParse,       /* Parse context */
  int op,              /* One of TK_UPDATE, TK_INSERT, TK_DELETE */
  ExprList *pChanges,  /* Changes list for any UPDATE OF triggers */
  int tr_tm,           /* One of TK_BEFORE, TK_AFTER */
  Table *pTab,         /* The table to code triggers from */
  int newIdx,          /* The indice of the "new" row to access */
  int oldIdx,          /* The indice of the "old" row to access */
  int orconf,          /* ON CONFLICT policy */
  int ignoreJump       /* Instruction to jump to for RAISE(IGNORE) */
){
  Trigger * pTrigger;
  TriggerStack * pTriggerStack;

  assert(op == TK_UPDATE || op == TK_INSERT || op == TK_DELETE);
  assert(tr_tm == TK_BEFORE || tr_tm == TK_AFTER );

  assert(newIdx != -1 || oldIdx != -1);

  pTrigger = pTab->pTrigger;
  while( pTrigger ){
    int fire_this = 0;

    /* determine whether we should code this trigger */
    if( pTrigger->op == op && pTrigger->tr_tm == tr_tm && 
        pTrigger->foreach == TK_ROW ){
      fire_this = 1;
      pTriggerStack = pParse->trigStack;
      while( pTriggerStack ){
        if( pTriggerStack->pTrigger == pTrigger ){
	  fire_this = 0;
	}
        pTriggerStack = pTriggerStack->pNext;
      }
      if( op == TK_UPDATE && pTrigger->pColumns &&
          !checkColumnOverLap(pTrigger->pColumns, pChanges) ){
        fire_this = 0;
      }
    }

    if( fire_this && (pTriggerStack = sqliteMalloc(sizeof(TriggerStack)))!=0 ){
      int endTrigger;
      SrcList dummyTablist;
      Expr * whenExpr;
      AuthContext sContext;

      dummyTablist.nSrc = 0;

      /* Push an entry on to the trigger stack */
      pTriggerStack->pTrigger = pTrigger;
      pTriggerStack->newIdx = newIdx;
      pTriggerStack->oldIdx = oldIdx;
      pTriggerStack->pTab = pTab;
      pTriggerStack->pNext = pParse->trigStack;
      pTriggerStack->ignoreJump = ignoreJump;
      pParse->trigStack = pTriggerStack;
      sqliteAuthContextPush(pParse, &sContext, pTrigger->name);

      /* code the WHEN clause */
      endTrigger = sqliteVdbeMakeLabel(pParse->pVdbe);
      whenExpr = sqliteExprDup(pTrigger->pWhen);
      if( sqliteExprResolveIds(pParse, &dummyTablist, 0, whenExpr) ){
        pParse->trigStack = pParse->trigStack->pNext;
        sqliteFree(pTriggerStack);
        sqliteExprDelete(whenExpr);
        return 1;
      }
      sqliteExprIfFalse(pParse, whenExpr, endTrigger, 1);
      sqliteExprDelete(whenExpr);

      sqliteVdbeAddOp(pParse->pVdbe, OP_ContextPush, 0, 0);
      codeTriggerProgram(pParse, pTrigger->step_list, orconf); 
      sqliteVdbeAddOp(pParse->pVdbe, OP_ContextPop, 0, 0);

      /* Pop the entry off the trigger stack */
      pParse->trigStack = pParse->trigStack->pNext;
      sqliteAuthContextPop(&sContext);
      sqliteFree(pTriggerStack);

      sqliteVdbeResolveLabel(pParse->pVdbe, endTrigger);
    }
    pTrigger = pTrigger->pNext;
  }

  return 0;
}