Initial commit

Signed-off-by: Mavridis Philippe <[email protected]>

1 files changed, 802 insertions, 0 deletions

diff --git a/src/sqlite/trigger.c b/src/sqlite/trigger.c
new file mode 100644
index 0000000..f39d2bd
--- /dev/null
+++ b/src/sqlite/trigger.c
@@ -0,0 +1,802 @@
+/*
+**
+** 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"
+
+#ifndef SQLITE_OMIT_TRIGGER
+/*
+** Delete a linked list of TriggerStep structures.
+*/
+void sqlite3DeleteTriggerStep(TriggerStep *pTriggerStep){
+  while( pTriggerStep ){
+    TriggerStep * pTmp = pTriggerStep;
+    pTriggerStep = pTriggerStep->pNext;
+
+    if( pTmp->target.dyn ) sqliteFree((char*)pTmp->target.z);
+    sqlite3ExprDelete(pTmp->pWhere);
+    sqlite3ExprListDelete(pTmp->pExprList);
+    sqlite3SelectDelete(pTmp->pSelect);
+    sqlite3IdListDelete(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
+** 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 = 0;
+  Table *pTab;
+  char *zName = 0;        /* Name of the trigger */
+  sqlite3 *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( 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"
+        " trigger on table: %S", pTableName, 0);
+    goto trigger_cleanup;
+  }
+
+#ifndef SQLITE_OMIT_AUTHORIZATION
+  {
+    int code = SQLITE_CREATE_TRIGGER;
+    const char *zDb = db->aDb[pTab->iDb].zName;
+    const char *zDbTrig = isTemp ? db->aDb[1].zName : zDb;
+    if( pTab->iDb==1 || isTemp ) code = SQLITE_CREATE_TEMP_TRIGGER;
+    if( sqlite3AuthCheck(pParse, code, zName, pTab->zName, zDbTrig) ){
+      goto trigger_cleanup;
+    }
+    if( sqlite3AuthCheck(pParse, SQLITE_INSERT, SCHEMA_TABLE(pTab->iDb),0,zDb)){
+      goto trigger_cleanup;
+    }
+  }
+#endif
+
+  /* INSTEAD OF triggers can only appear on views and BEFORE 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 */
+  pTrigger = (Trigger*)sqliteMalloc(sizeof(Trigger));
+  if( pTrigger==0 ) goto trigger_cleanup;
+  pTrigger->name = zName;
+  zName = 0;
+  pTrigger->table = sqliteStrDup(pTableName->a[0].zName);
+  pTrigger->iDb = iDb;
+  pTrigger->iTabDb = pTab->iDb;
+  pTrigger->op = op;
+  pTrigger->tr_tm = tr_tm==TK_BEFORE ? TRIGGER_BEFORE : TRIGGER_AFTER;
+  pTrigger->pWhen = sqlite3ExprDup(pWhen);
+  pTrigger->pColumns = sqlite3IdListDup(pColumns);
+  pTrigger->foreach = foreach;
+  sqlite3TokenCopy(&pTrigger->nameToken,pName);
+  assert( pParse->pNewTrigger==0 );
+  pParse->pNewTrigger = pTrigger;
+
+trigger_cleanup:
+  sqliteFree(zName);
+  sqlite3SrcListDelete(pTableName);
+  sqlite3IdListDelete(pColumns);
+  sqlite3ExprDelete(pWhen);
+  if( !pParse->pNewTrigger ){
+    sqlite3DeleteTrigger(pTrigger);
+  }else{
+    assert( pParse->pNewTrigger==pTrigger );
+  }
+}
+
+/*
+** This routine is called after all of the trigger actions have been parsed
+** in order to complete the process of building the trigger.
+*/
+void sqlite3FinishTrigger(
+  Parse *pParse,          /* Parser context */
+  TriggerStep *pStepList, /* The triggered program */
+  Token *pAll             /* Token that describes the complete CREATE TRIGGER */
+){
+  Trigger *pTrig = 0;     /* The trigger whose construction is finishing up */
+  sqlite3 *db = pParse->db;  /* The database */
+  DbFixer sFix;
+
+  pTrig = pParse->pNewTrigger;
+  pParse->pNewTrigger = 0;
+  if( pParse->nErr || pTrig==0 ) goto triggerfinish_cleanup;
+  pTrig->step_list = pStepList;
+  while( pStepList ){
+    pStepList->pTrig = pTrig;
+    pStepList = pStepList->pNext;
+  }
+  if( sqlite3FixInit(&sFix, pParse, pTrig->iDb, "trigger", &pTrig->nameToken) 
+          && sqlite3FixTriggerStep(&sFix, pTrig->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 const VdbeOpList insertTrig[] = {
+      { OP_NewRowid,   0, 0,  0          },
+      { OP_String8,    0, 0,  "trigger"  },
+      { OP_String8,    0, 0,  0          },  /* 2: trigger name */
+      { OP_String8,    0, 0,  0          },  /* 3: table name */
+      { OP_Integer,    0, 0,  0          },
+      { OP_String8,    0, 0,  "CREATE TRIGGER "},
+      { OP_String8,    0, 0,  0          },  /* 6: SQL */
+      { OP_Concat,     0, 0,  0          }, 
+      { OP_MakeRecord, 5, 0,  "tttit"    },
+      { OP_Insert,     0, 0,  0          },
+    };
+    int addr;
+    Vdbe *v;
+
+    /* Make an entry in the sqlite_master table */
+    v = sqlite3GetVdbe(pParse);
+    if( v==0 ) goto triggerfinish_cleanup;
+    sqlite3BeginWriteOperation(pParse, 0, pTrig->iDb);
+    sqlite3OpenMasterTable(v, pTrig->iDb);
+    addr = sqlite3VdbeAddOpList(v, ArraySize(insertTrig), insertTrig);
+    sqlite3VdbeChangeP3(v, addr+2, pTrig->name, 0); 
+    sqlite3VdbeChangeP3(v, addr+3, pTrig->table, 0); 
+    sqlite3VdbeChangeP3(v, addr+6, pAll->z, pAll->n);
+    sqlite3ChangeCookie(db, v, pTrig->iDb);
+    sqlite3VdbeAddOp(v, OP_Close, 0, 0);
+    sqlite3VdbeOp3(v, OP_ParseSchema, pTrig->iDb, 0, 
+       sqlite3MPrintf("type='trigger' AND name='%q'", pTrig->name), P3_DYNAMIC);
+  }
+
+  if( db->init.busy ){
+    Table *pTab;
+    Trigger *pDel;
+    pDel = sqlite3HashInsert(&db->aDb[pTrig->iDb].trigHash, 
+                     pTrig->name, strlen(pTrig->name)+1, pTrig);
+    if( pDel ){
+      assert( sqlite3_malloc_failed && pDel==pTrig );
+      goto triggerfinish_cleanup;
+    }
+    pTab = sqlite3LocateTable(pParse,pTrig->table,db->aDb[pTrig->iTabDb].zName);
+    assert( pTab!=0 );
+    pTrig->pNext = pTab->pTrigger;
+    pTab->pTrigger = pTrig;
+    pTrig = 0;
+  }
+
+triggerfinish_cleanup:
+  sqlite3DeleteTrigger(pTrig);
+  assert( !pParse->pNewTrigger );
+  sqlite3DeleteTriggerStep(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 sqlite3_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 sqlite3_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 = sqlite3SelectDup(p->pSelect);
+    sqlite3SelectDelete(p->pSelect);
+    p->pSelect = pNew;
+  }
+  if( p->pWhere ){
+    Expr *pNew = sqlite3ExprDup(p->pWhere);
+    sqlite3ExprDelete(p->pWhere);
+    p->pWhere = pNew;
+  }
+  if( p->pExprList ){
+    ExprList *pNew = sqlite3ExprListDup(p->pExprList);
+    sqlite3ExprListDelete(p->pExprList);
+    p->pExprList = pNew;
+  }
+  if( p->pIdList ){
+    IdList *pNew = sqlite3IdListDup(p->pIdList);
+    sqlite3IdListDelete(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 *sqlite3TriggerSelectStep(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 *sqlite3TriggerInsertStep(
+  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));
+
+  assert(pEList == 0 || pSelect == 0);
+  assert(pEList != 0 || pSelect != 0);
+
+  if( pTriggerStep ){
+    pTriggerStep->op = TK_INSERT;
+    pTriggerStep->pSelect = pSelect;
+    pTriggerStep->target  = *pTableName;
+    pTriggerStep->pIdList = pColumn;
+    pTriggerStep->pExprList = pEList;
+    pTriggerStep->orconf = orconf;
+    sqlitePersistTriggerStep(pTriggerStep);
+  }else{
+    sqlite3IdListDelete(pColumn);
+    sqlite3ExprListDelete(pEList);
+    sqlite3SelectDup(pSelect);
+  }
+
+  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 *sqlite3TriggerUpdateStep(
+  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 *sqlite3TriggerDeleteStep(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 sqlite3DeleteTrigger(Trigger *pTrigger){
+  if( pTrigger==0 ) return;
+  sqlite3DeleteTriggerStep(pTrigger->step_list);
+  sqliteFree(pTrigger->name);
+  sqliteFree(pTrigger->table);
+  sqlite3ExprDelete(pTrigger->pWhen);
+  sqlite3IdListDelete(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 sqlite3DropTriggerPtr() routine does the
+** same job as this routine except it takes a pointer to the trigger
+** instead of the trigger name.
+**/
+void sqlite3DropTrigger(Parse *pParse, SrcList *pName){
+  Trigger *pTrigger = 0;
+  int i;
+  const char *zDb;
+  const char *zName;
+  int nName;
+  sqlite3 *db = pParse->db;
+
+  if( sqlite3_malloc_failed ) goto drop_trigger_cleanup;
+  if( SQLITE_OK!=sqlite3ReadSchema(pParse) ){
+    goto drop_trigger_cleanup;
+  }
+
+  assert( pName->nSrc==1 );
+  zDb = pName->a[0].zDatabase;
+  zName = pName->a[0].zName;
+  nName = strlen(zName);
+  for(i=OMIT_TEMPDB; i<db->nDb; i++){
+    int j = (i<2) ? i^1 : i;  /* Search TEMP before MAIN */
+    if( zDb && sqlite3StrICmp(db->aDb[j].zName, zDb) ) continue;
+    pTrigger = sqlite3HashFind(&(db->aDb[j].trigHash), zName, nName+1);
+    if( pTrigger ) break;
+  }
+  if( !pTrigger ){
+    sqlite3ErrorMsg(pParse, "no such trigger: %S", pName, 0);
+    goto drop_trigger_cleanup;
+  }
+  sqlite3DropTriggerPtr(pParse, pTrigger, 0);
+
+drop_trigger_cleanup:
+  sqlite3SrcListDelete(pName);
+}
+
+/*
+** Return a pointer to the Table structure for the table that a trigger
+** is set on.
+*/
+static Table *tableOfTrigger(sqlite3 *db, Trigger *pTrigger){
+  return sqlite3FindTable(db,pTrigger->table,db->aDb[pTrigger->iTabDb].zName);
+}
+
+
+/*
+** 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 sqlite3DropTriggerPtr(Parse *pParse, Trigger *pTrigger, int nested){
+  Table   *pTable;
+  Vdbe *v;
+  sqlite3 *db = pParse->db;
+  int iDb;
+
+  iDb = pTrigger->iDb;
+  assert( iDb>=0 && iDb<db->nDb );
+  pTable = tableOfTrigger(db, pTrigger);
+  assert(pTable);
+  assert( pTable->iDb==iDb || iDb==1 );
+#ifndef SQLITE_OMIT_AUTHORIZATION
+  {
+    int code = SQLITE_DROP_TRIGGER;
+    const char *zDb = db->aDb[iDb].zName;
+    const char *zTab = SCHEMA_TABLE(iDb);
+    if( iDb==1 ) code = SQLITE_DROP_TEMP_TRIGGER;
+    if( sqlite3AuthCheck(pParse, code, pTrigger->name, pTable->zName, zDb) ||
+      sqlite3AuthCheck(pParse, SQLITE_DELETE, zTab, 0, zDb) ){
+      return;
+    }
+  }
+#endif
+
+  /* Generate code to destroy the database record of the trigger.
+  */
+  if( pTable!=0 && (v = sqlite3GetVdbe(pParse))!=0 ){
+    int base;
+    static const VdbeOpList dropTrigger[] = {
+      { OP_Rewind,     0, ADDR(9),  0},
+      { OP_String8,    0, 0,        0}, /* 1 */
+      { OP_Column,     0, 1,        0},
+      { OP_Ne,         0, ADDR(8),  0},
+      { OP_String8,    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 */
+    };
+
+    sqlite3BeginWriteOperation(pParse, 0, iDb);
+    sqlite3OpenMasterTable(v, iDb);
+    base = sqlite3VdbeAddOpList(v,  ArraySize(dropTrigger), dropTrigger);
+    sqlite3VdbeChangeP3(v, base+1, pTrigger->name, 0);
+    sqlite3ChangeCookie(db, v, iDb);
+    sqlite3VdbeAddOp(v, OP_Close, 0, 0);
+    sqlite3VdbeOp3(v, OP_DropTrigger, iDb, 0, pTrigger->name, 0);
+  }
+}
+
+/*
+** Remove a trigger from the hash tables of the sqlite* pointer.
+*/
+void sqlite3UnlinkAndDeleteTrigger(sqlite3 *db, int iDb, const char *zName){
+  Trigger *pTrigger;
+  int nName = strlen(zName);
+  pTrigger = sqlite3HashInsert(&(db->aDb[iDb].trigHash), zName, nName+1, 0);
+  if( pTrigger ){
+    Table *pTable = tableOfTrigger(db, pTrigger);
+    assert( pTable!=0 );
+    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);
+    }
+    sqlite3DeleteTrigger(pTrigger);
+    db->flags |= SQLITE_InternChanges;
+  }
+}
+
+/*
+** 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( sqlite3IdListIndex(pIdList, pEList->a[e].zName)>=0 ) return 1;
+  }
+  return 0; 
+}
+
+/*
+** Return a bit vector to indicate what kind of triggers exist for operation
+** "op" on table pTab.  If pChanges is not NULL then it is a list of columns
+** that are being updated.  Triggers only match if the ON clause of the
+** trigger definition overlaps the set of columns being updated.
+**
+** The returned bit vector is some combination of TRIGGER_BEFORE and
+** TRIGGER_AFTER.
+*/
+int sqlite3TriggersExist(
+  Parse *pParse,          /* Used to check for recursive triggers */
+  Table *pTab,            /* The table the contains the triggers */
+  int op,                 /* one of TK_DELETE, TK_INSERT, TK_UPDATE */
+  ExprList *pChanges      /* Columns that change in an UPDATE statement */
+){
+  Trigger *pTrigger = pTab->pTrigger;
+  int mask = 0;
+
+  while( pTrigger ){
+    if( pTrigger->op==op && checkColumnOverLap(pTrigger->pColumns, pChanges) ){
+      TriggerStack *ss;
+      ss = pParse->trigStack;
+      while( ss && ss->pTrigger!=pTab->pTrigger ){
+	ss = ss->pNext;
+      }
+      if( ss==0 ){
+        mask |= pTrigger->tr_tm;
+      }
+    }
+    pTrigger = pTrigger->pNext;
+  }
+  return mask;
+}
+
+/*
+** 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 = sqlite3SrcListAppend(0, &sDb, &pStep->target);
+  } else {
+    pSrc = sqlite3SrcListAppend(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;
+  Vdbe *v = pParse->pVdbe;
+
+  assert( pTriggerStep!=0 );
+  assert( v!=0 );
+  sqlite3VdbeAddOp(v, OP_ContextPush, 0, 0);
+  VdbeComment((v, "# begin trigger %s", pStepList->pTrig->name));
+  while( pTriggerStep ){
+    orconf = (orconfin == OE_Default)?pTriggerStep->orconf:orconfin;
+    pParse->trigStack->orconf = orconf;
+    switch( pTriggerStep->op ){
+      case TK_SELECT: {
+	Select * ss = sqlite3SelectDup(pTriggerStep->pSelect);		  
+	assert(ss);
+	assert(ss->pSrc);
+        sqlite3SelectResolve(pParse, ss, 0);
+	sqlite3Select(pParse, ss, SRT_Discard, 0, 0, 0, 0, 0);
+	sqlite3SelectDelete(ss);
+	break;
+      }
+      case TK_UPDATE: {
+        SrcList *pSrc;
+        pSrc = targetSrcList(pParse, pTriggerStep);
+        sqlite3VdbeAddOp(v, OP_ResetCount, 0, 0);
+        sqlite3Update(pParse, pSrc,
+		sqlite3ExprListDup(pTriggerStep->pExprList), 
+		sqlite3ExprDup(pTriggerStep->pWhere), orconf);
+        sqlite3VdbeAddOp(v, OP_ResetCount, 1, 0);
+        break;
+      }
+      case TK_INSERT: {
+        SrcList *pSrc;
+        pSrc = targetSrcList(pParse, pTriggerStep);
+        sqlite3VdbeAddOp(v, OP_ResetCount, 0, 0);
+        sqlite3Insert(pParse, pSrc,
+          sqlite3ExprListDup(pTriggerStep->pExprList), 
+          sqlite3SelectDup(pTriggerStep->pSelect), 
+          sqlite3IdListDup(pTriggerStep->pIdList), orconf);
+        sqlite3VdbeAddOp(v, OP_ResetCount, 1, 0);
+        break;
+      }
+      case TK_DELETE: {
+        SrcList *pSrc;
+        sqlite3VdbeAddOp(v, OP_ResetCount, 0, 0);
+        pSrc = targetSrcList(pParse, pTriggerStep);
+        sqlite3DeleteFrom(pParse, pSrc, sqlite3ExprDup(pTriggerStep->pWhere));
+        sqlite3VdbeAddOp(v, OP_ResetCount, 1, 0);
+        break;
+      }
+      default:
+        assert(0);
+    } 
+    pTriggerStep = pTriggerStep->pNext;
+  }
+  sqlite3VdbeAddOp(v, OP_ContextPop, 0, 0);
+  VdbeComment((v, "# end trigger %s", pStepList->pTrig->name));
+
+  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 sqlite3CodeRowTrigger(
+  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 TRIGGER_BEFORE, TRIGGER_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 *pStack;
+  TriggerStack trigStackEntry;
+
+  assert(op == TK_UPDATE || op == TK_INSERT || op == TK_DELETE);
+  assert(tr_tm == TRIGGER_BEFORE || tr_tm == TRIGGER_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 ){
+      fire_this = 1;
+      for(pStack=pParse->trigStack; pStack; pStack=pStack->pNext){
+        if( pStack->pTrigger==pTrigger ){
+	  fire_this = 0;
+	}
+      }
+      if( op == TK_UPDATE && pTrigger->pColumns &&
+          !checkColumnOverLap(pTrigger->pColumns, pChanges) ){
+        fire_this = 0;
+      }
+    }
+ 
+    if( fire_this ){
+      int endTrigger;
+      Expr * whenExpr;
+      AuthContext sContext;
+      NameContext sNC;
+
+      memset(&sNC, 0, sizeof(sNC));
+      sNC.pParse = pParse;
+
+      /* Push an entry on to the trigger stack */
+      trigStackEntry.pTrigger = pTrigger;
+      trigStackEntry.newIdx = newIdx;
+      trigStackEntry.oldIdx = oldIdx;
+      trigStackEntry.pTab = pTab;
+      trigStackEntry.pNext = pParse->trigStack;
+      trigStackEntry.ignoreJump = ignoreJump;
+      pParse->trigStack = &trigStackEntry;
+      sqlite3AuthContextPush(pParse, &sContext, pTrigger->name);
+
+      /* code the WHEN clause */
+      endTrigger = sqlite3VdbeMakeLabel(pParse->pVdbe);
+      whenExpr = sqlite3ExprDup(pTrigger->pWhen);
+      if( sqlite3ExprResolveNames(&sNC, whenExpr) ){
+        pParse->trigStack = trigStackEntry.pNext;
+        sqlite3ExprDelete(whenExpr);
+        return 1;
+      }
+      sqlite3ExprIfFalse(pParse, whenExpr, endTrigger, 1);
+      sqlite3ExprDelete(whenExpr);
+
+      codeTriggerProgram(pParse, pTrigger->step_list, orconf); 
+
+      /* Pop the entry off the trigger stack */
+      pParse->trigStack = trigStackEntry.pNext;
+      sqlite3AuthContextPop(&sContext);
+
+      sqlite3VdbeResolveLabel(pParse->pVdbe, endTrigger);
+    }
+    pTrigger = pTrigger->pNext;
+  }
+  return 0;
+}
+#endif /* !defined(SQLITE_OMIT_TRIGGER) */