trigger.c

sqlite数据库管理系统开放源码

/*
**
** 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.
**
*************************************************************************
*
*/
#include "sqliteInt.h"

/*
** Delete a linked list of TriggerStep structures.
*/
void sqliteDeleteTriggerStep(TriggerStep *pTriggerStep){
  while( pTriggerStep ){
    TriggerStep * pTmp = pTriggerStep;
    pTriggerStep = pTriggerStep->pNext;

    if( pTmp->target.dyn ) sqliteFree((char*)pTmp->target.z);
    sqliteExprDelete(pTmp->pWhere);
    sqliteExprListDelete(pTmp->pExprList);
    sqliteSelectDelete(pTmp->pSelect);
    sqliteIdListDelete(pTmp->pIdList);

    sqliteFree(pTmp);
  }
}

/*
** 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
** sqliteFinishTrigger() function is called to complete the trigger
** construction process.
*/
void sqliteBeginTrigger(
  Parse *pParse,      /* The parse context of the CREATE TRIGGER statement */
  Token *pName,       /* 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 *nt;
  Table   *tab;
  char *zName = 0;        /* Name of the trigger */
  sqlite *db = pParse->db;
  int iDb;                /* When database to store the trigger in */
  DbFixer sFix;

  /* Check that: 
  ** 1. the trigger name does not already exist.
  ** 2. the table (or view) does exist in the same database as the trigger.
  ** 3. that we are not trying to create a trigger on the sqlite_master table
  ** 4. That we are not trying to create an INSTEAD OF trigger on a table.
  ** 5. That we are not trying to create a BEFORE or AFTER trigger on a view.
  */
  if( sqlite_malloc_failed ) goto trigger_cleanup;
  assert( pTableName->nSrc==1 );
  if( db->init.busy
   && sqliteFixInit(&sFix, pParse, db->init.iDb, "trigger", pName)
   && sqliteFixSrcList(&sFix, pTableName)
  ){
    goto trigger_cleanup;
  }
  tab = sqliteSrcListLookup(pParse, pTableName);
  if( !tab ){
    goto trigger_cleanup;
  }
  iDb = isTemp ? 1 : tab->iDb;
  if( iDb>=2 && !db->init.busy ){
    sqliteErrorMsg(pParse, "triggers may not be added to auxiliary "
       "database %s", db->aDb[tab->iDb].zName);
    goto trigger_cleanup;
  }

  zName = sqliteStrNDup(pName->z, pName->n);
  sqliteDequote(zName);
  if( sqliteHashFind(&(db->aDb[iDb].trigHash), zName,pName->n+1) ){
    sqliteErrorMsg(pParse, "trigger %T already exists", pName);
    goto trigger_cleanup;
  }
  if( sqliteStrNICmp(tab->zName, "sqlite_", 7)==0 ){
    sqliteErrorMsg(pParse, "cannot create trigger on system table");
    pParse->nErr++;
    goto trigger_cleanup;
  }
  if( tab->pSelect && tr_tm != TK_INSTEAD ){
    sqliteErrorMsg(pParse, "cannot create %s trigger on view: %S", 
        (tr_tm == TK_BEFORE)?"BEFORE":"AFTER", pTableName, 0);
    goto trigger_cleanup;
  }
  if( !tab->pSelect && tr_tm == TK_INSTEAD ){
    sqliteErrorMsg(pParse, "cannot create INSTEAD OF"
        " trigger on table: %S", pTableName, 0);
    goto trigger_cleanup;
  }
#ifndef SQLITE_OMIT_AUTHORIZATION
  {
    int code = SQLITE_CREATE_TRIGGER;
    const char *zDb = db->aDb[tab->iDb].zName;
    const char *zDbTrig = isTemp ? db->aDb[1].zName : zDb;
    if( tab->iDb==1 || isTemp ) code = SQLITE_CREATE_TEMP_TRIGGER;
    if( sqliteAuthCheck(pParse, code, zName, tab->zName, zDbTrig) ){
      goto trigger_cleanup;
    }
    if( sqliteAuthCheck(pParse, SQLITE_INSERT, SCHEMA_TABLE(tab->iDb), 0, zDb)){
      goto trigger_cleanup;
    }
  }
#endif

  /* INSTEAD OF triggers can only appear on views and BEGIN triggers
  ** cannot appear on views.  So we might as well translate every
  ** INSTEAD OF trigger into a BEFORE trigger.  It simplifies code
  ** elsewhere.
  */
  if (tr_tm == TK_INSTEAD){
    tr_tm = TK_BEFORE;
  }

  /* Build the Trigger object */
  nt = (Trigger*)sqliteMalloc(sizeof(Trigger));
  if( nt==0 ) goto trigger_cleanup;
  nt->name = zName;
  zName = 0;
  nt->table = sqliteStrDup(pTableName->a[0].zName);
  if( sqlite_malloc_failed ) goto trigger_cleanup;
  nt->iDb = iDb;
  nt->iTabDb = tab->iDb;
  nt->op = op;
  nt->tr_tm = tr_tm;
  nt->pWhen = sqliteExprDup(pWhen);
  nt->pColumns = sqliteIdListDup(pColumns);
  nt->foreach = foreach;
  sqliteTokenCopy(&nt->nameToken,pName);
  assert( pParse->pNewTrigger==0 );
  pParse->pNewTrigger = nt;

trigger_cleanup:
  sqliteFree(zName);
  sqliteSrcListDelete(pTableName);
  sqliteIdListDelete(pColumns);
  sqliteExprDelete(pWhen);
}

/*
** This routine is called after all of the trigger actions have been parsed
** in order to complete the process of building the trigger.
*/
void sqliteFinishTrigger(
  Parse *pParse,          /* Parser context */
  TriggerStep *pStepList, /* The triggered program */
  Token *pAll             /* Token that describes the complete CREATE TRIGGER */
){
  Trigger *nt = 0;          /* The trigger whose construction is finishing up */
  sqlite *db = pParse->db;  /* The database */
  DbFixer sFix;

  if( pParse->nErr || pParse->pNewTrigger==0 ) goto triggerfinish_cleanup;
  nt = pParse->pNewTrigger;
  pParse->pNewTrigger = 0;
  nt->step_list = pStepList;
  while( pStepList ){
    pStepList->pTrig = nt;
    pStepList = pStepList->pNext;
  }
  if( sqliteFixInit(&sFix, pParse, nt->iDb, "trigger", &nt->nameToken) 
          && sqliteFixTriggerStep(&sFix, nt->step_list) ){
    goto triggerfinish_cleanup;
  }

  /* if we are not initializing, and this trigger is not on a TEMP table, 
  ** build the sqlite_master entry
  */
  if( !db->init.busy ){
    static VdbeOpList insertTrig[] = {
      { OP_NewRecno,   0, 0,  0          },
      { OP_String,     0, 0,  "trigger"  },
      { OP_String,     0, 0,  0          },  /* 2: trigger name */
      { OP_String,     0, 0,  0          },  /* 3: table name */
      { OP_Integer,    0, 0,  0          },
      { OP_String,     0, 0,  0          },  /* 5: SQL */
      { OP_MakeRecord, 5, 0,  0          },
      { OP_PutIntKey,  0, 0,  0          },
    };
    int addr;
    Vdbe *v;

    /* Make an entry in the sqlite_master table */
    v = sqliteGetVdbe(pParse);
    if( v==0 ) goto triggerfinish_cleanup;
    sqliteBeginWriteOperation(pParse, 0, 0);
    sqliteOpenMasterTable(v, nt->iDb);
    addr = sqliteVdbeAddOpList(v, ArraySize(insertTrig), insertTrig);
    sqliteVdbeChangeP3(v, addr+2, nt->name, 0); 
    sqliteVdbeChangeP3(v, addr+3, nt->table, 0); 
    sqliteVdbeChangeP3(v, addr+5, pAll->z, pAll->n);
    if( nt->iDb==0 ){
      sqliteChangeCookie(db, v);
    }
    sqliteVdbeAddOp(v, OP_Close, 0, 0);
    sqliteEndWriteOperation(pParse);
  }

  if( !pParse->explain ){
    Table *pTab;
    sqliteHashInsert(&db->aDb[nt->iDb].trigHash, 
                     nt->name, strlen(nt->name)+1, nt);
    pTab = sqliteLocateTable(pParse, nt->table, db->aDb[nt->iTabDb].zName);
    assert( pTab!=0 );
    nt->pNext = pTab->pTrigger;
    pTab->pTrigger = nt;
    nt = 0;
  }

triggerfinish_cleanup:
  sqliteDeleteTrigger(nt);
  sqliteDeleteTrigger(pParse->pNewTrigger);
  pParse->pNewTrigger = 0;
  sqliteDeleteTriggerStep(pStepList);
}

/*
** Make a copy of all components of the given trigger step.  This has
** the effect of copying all Expr.token.z values into memory obtained
** from sqliteMalloc().  As initially created, the Expr.token.z values
** all point to the input string that was fed to the parser.  But that
** string is ephemeral - it will go away as soon as the sqlite_exec()
** call that started the parser exits.  This routine makes a persistent
** copy of all the Expr.token.z strings so that the TriggerStep structure
** will be valid even after the sqlite_exec() call returns.
*/
static void sqlitePersistTriggerStep(TriggerStep *p){
  if( p->target.z ){
    p->target.z = sqliteStrNDup(p->target.z, p->target.n);
    p->target.dyn = 1;
  }
  if( p->pSelect ){
    Select *pNew = sqliteSelectDup(p->pSelect);
    sqliteSelectDelete(p->pSelect);
    p->pSelect = pNew;
  }
  if( p->pWhere ){
    Expr *pNew = sqliteExprDup(p->pWhere);
    sqliteExprDelete(p->pWhere);
    p->pWhere = pNew;
  }
  if( p->pExprList ){
    ExprList *pNew = sqliteExprListDup(p->pExprList);
    sqliteExprListDelete(p->pExprList);
    p->pExprList = pNew;
  }
  if( p->pIdList ){
    IdList *pNew = sqliteIdListDup(p->pIdList);
    sqliteIdListDelete(p->pIdList);
    p->pIdList = pNew;
  }
}

/*
** Turn a SELECT statement (that the pSelect parameter points to) into
** a trigger step.  Return a pointer to a TriggerStep structure.
**
** The parser calls this routine when it finds a SELECT statement in
** body of a TRIGGER.  
*/
TriggerStep *sqliteTriggerSelectStep(Select *pSelect){
  TriggerStep *pTriggerStep = sqliteMalloc(sizeof(TriggerStep));
  if( pTriggerStep==0 ) return 0;

  pTriggerStep->op = TK_SELECT;
  pTriggerStep->pSelect = pSelect;
  pTriggerStep->orconf = OE_Default;
  sqlitePersistTriggerStep(pTriggerStep);

  return pTriggerStep;
}

/*
** Build a trigger step out of an INSERT statement.  Return a pointer
** to the new trigger step.
**
** The parser calls this routine when it sees an INSERT inside the
** body of a trigger.
*/
TriggerStep *sqliteTriggerInsertStep(
  Token *pTableName,  /* Name of the table into which we insert */
  IdList *pColumn,    /* List of columns in pTableName to insert into */
  ExprList *pEList,   /* The VALUE clause: a list of values to be inserted */
  Select *pSelect,    /* A SELECT statement that supplies values */
  int orconf          /* The conflict algorithm (OE_Abort, OE_Replace, etc.) */
){
  TriggerStep *pTriggerStep = sqliteMalloc(sizeof(TriggerStep));
  if( pTriggerStep==0 ) return 0;

  assert(pEList == 0 || pSelect == 0);
  assert(pEList != 0 || pSelect != 0);

  pTriggerStep->op = TK_INSERT;
  pTriggerStep->pSelect = pSelect;
  pTriggerStep->target  = *pTableName;
  pTriggerStep->pIdList = pColumn;
  pTriggerStep->pExprList = pEList;
  pTriggerStep->orconf = orconf;
  sqlitePersistTriggerStep(pTriggerStep);

  return pTriggerStep;
}

/*
** Construct a trigger step that implements an UPDATE statement and return
** a pointer to that trigger step.  The parser calls this routine when it
** sees an UPDATE statement inside the body of a CREATE TRIGGER.
*/
TriggerStep *sqliteTriggerUpdateStep(
  Token *pTableName,   /* Name of the table to be updated */
  ExprList *pEList,    /* The SET clause: list of column and new values */
  Expr *pWhere,        /* The WHERE clause */
  int orconf           /* The conflict algorithm. (OE_Abort, OE_Ignore, etc) */
){
  TriggerStep *pTriggerStep = sqliteMalloc(sizeof(TriggerStep));
  if( pTriggerStep==0 ) return 0;

  pTriggerStep->op = TK_UPDATE;
  pTriggerStep->target  = *pTableName;
  pTriggerStep->pExprList = pEList;
  pTriggerStep->pWhere = pWhere;
  pTriggerStep->orconf = orconf;
  sqlitePersistTriggerStep(pTriggerStep);

  return pTriggerStep;
}

/*
** Construct a trigger step that implements a DELETE statement and return
** a pointer to that trigger step.  The parser calls this routine when it
** sees a DELETE statement inside the body of a CREATE TRIGGER.
*/
TriggerStep *sqliteTriggerDeleteStep(Token *pTableName, Expr *pWhere){
  TriggerStep *pTriggerStep = sqliteMalloc(sizeof(TriggerStep));
  if( pTriggerStep==0 ) return 0;

  pTriggerStep->op = TK_DELETE;
  pTriggerStep->target  = *pTableName;
  pTriggerStep->pWhere = pWhere;
  pTriggerStep->orconf = OE_Default;
  sqlitePersistTriggerStep(pTriggerStep);

  return pTriggerStep;
}

/* 
** Recursively delete a Trigger structure
*/
void sqliteDeleteTrigger(Trigger *pTrigger){
  if( pTrigger==0 ) return;
  sqliteDeleteTriggerStep(pTrigger->step_list);
  sqliteFree(pTrigger->name);
  sqliteFree(pTrigger->table);
  sqliteExprDelete(pTrigger->pWhen);
  sqliteIdListDelete(pTrigger->pColumns);
  if( pTrigger->nameToken.dyn ) sqliteFree((char*)pTrigger->nameToken.z);
  sqliteFree(pTrigger);
}

/*
 * This function is called to drop a trigger from the database schema. 
 *
 * This may be called directly from the parser and therefore identifies
 * the trigger by name.  The sqliteDropTriggerPtr() routine does the
 * same job as this routine except it take a spointer to the trigger
 * instead of the trigger name.
 *
 * Note that this function does not delete the trigger entirely. Instead it