SQLite

  }
  testcase( w.eCode==0 );
  testcase( w.eCode==CKCNSTRNT_COLUMN );
  testcase( w.eCode==CKCNSTRNT_ROWID );
  testcase( w.eCode==(CKCNSTRNT_ROWID|CKCNSTRNT_COLUMN) );
  return !w.eCode;
}

/*
** An instance of the ConstraintAddr object remembers the byte-code addresses
** for sections of the constraint checks that deal with uniqueness constraints
** on the rowid and on the upsert constraint.
**
** This information is passed into checkReorderConstraintChecks() to insert
** some OP_Goto operations so that the rowid and upsert constraints occur
** in the correct order relative to other constraints.
*/
typedef struct ConstraintAddr ConstraintAddr;
struct ConstraintAddr {
  int ipkTop;          /* Subroutine for rowid constraint check */
  int upsertTop;       /* Label for upsert constraint check subroutine */
  int ipkBtm;          /* Return opcode rowid constraint check */
  int upsertBtm;       /* upsert constraint returns to this label */
};

/*
** Generate any OP_Goto operations needed to cause constraints to be
** run that haven't already been run.
*/
static void reorderConstraintChecks(Vdbe *v, ConstraintAddr *p){
  if( p->upsertTop ){
    sqlite3VdbeGoto(v, p->upsertTop);
    VdbeComment((v, "call upsert subroutine"));
    sqlite3VdbeResolveLabel(v, p->upsertBtm);
    p->upsertTop = 0;
  }
  if( p->ipkTop ){
    sqlite3VdbeGoto(v, p->ipkTop);
    VdbeComment((v, "call rowid constraint-check subroutine"));
    sqlite3VdbeJumpHere(v, p->ipkBtm);
    p->ipkTop = 0;
  }
}

/*
** Generate code to do constraint checks prior to an INSERT or an UPDATE
** on table pTab.
**
** The regNewData parameter is the first register in a range that contains
** the data to be inserted or the data after the update.  There will be

  int i;               /* loop counter */
  int ix;              /* Index loop counter */
  int nCol;            /* Number of columns */
  int onError;         /* Conflict resolution strategy */
  int addr1;           /* Address of jump instruction */
  int seenReplace = 0; /* True if REPLACE is used to resolve INT PK conflict */
  int nPkField;        /* Number of fields in PRIMARY KEY. 1 for ROWID tables */
  ConstraintAddr sAddr;/* Address information for constraint reordering */
  Index *pUpIdx = 0;   /* Index to which to apply the upsert */
  u8 isUpdate;         /* True if this is an UPDATE operation */
  u8 bAffinityDone = 0;  /* True if the OP_Affinity operation has been run */
  int upsertBypass = 0;  /* Address of Goto to bypass upsert subroutine */

  isUpdate = regOldData!=0;
  db = pParse->db;
  v = sqlite3GetVdbe(pParse);
  assert( v!=0 );
  assert( pTab->pSelect==0 );  /* This table is not a VIEW */
  nCol = pTab->nCol;
  sAddr.ipkTop = 0;
  sAddr.upsertTop = 0;
  
  /* pPk is the PRIMARY KEY index for WITHOUT ROWID tables and NULL for
  ** normal rowid tables.  nPkField is the number of key fields in the 
  ** pPk index or 1 for a rowid table.  In other words, nPkField is the
  ** number of fields in the true primary key of the table. */
  if( HasRowid(pTab) ){
    pPk = 0;

                              P5_ConstraintCheck);
      }
      sqlite3VdbeResolveLabel(v, allOk);
    }
    pParse->iSelfTab = 0;
  }
#endif /* !defined(SQLITE_OMIT_CHECK) */

  /* UNIQUE and PRIMARY KEY constraints should be handled in the following
  ** order:
  **
  **   (1)  OE_Abort, OE_Fail, OE_Rollback, OE_Ignore
  **   (2)  OE_Update
  **   (3)  OE_Replace
  **
  ** OE_Fail and OE_Ignore must happen before any changes are made.
  ** OE_Update guarantees that only a single row will change, so it
  ** must happen before OE_Replace.  Technically, OE_Abort and OE_Rollback
  ** could happen in any order, but they are grouped up front for
  ** convenience.
  **
  ** Constraint checking code is generated in this order:
  **   (A)  The rowid constraint
  **   (B)  Unique index constraints that do not have OE_Replace as their
  **        default conflict resolution strategy
  **   (C)  Unique index that do use OE_Replace by default.
  **
  ** The ordering of (2) and (3) is accomplished by making sure the linked
  ** list of indexes attached to a table puts all OE_Replace indexes last
  ** in the list.  See sqlite3CreateIndex() for where that happens.
  */

  /* If there is an ON CONFLICT clause without a constraint-target
  ** (In other words, one of "ON CONFLICT DO NOTHING" or
  ** "ON DUPLICATION KEY UPDATE") then change the overrideError to
  ** whichever is appropriate.
  */
  if( pUpsert ){
    if( pUpsert->pUpsertTarget==0 ){
      if( pUpsert->pUpsertSet==0 ){
        /* An ON CONFLICT DO NOTHING clause, without a constraint-target.
        ** Make all unique constraint resolution be OE_Ignore */
        overrideError = OE_Ignore;
        pUpsert = 0;
      }else{
        /* An ON DUPLICATE KEY UPDATE clause.  All unique constraints
        ** do upsert processing */
        overrideError = OE_Update;
      }
    }else if( (pUpIdx = pUpsert->pUpsertIdx)!=0 ){
      sAddr.upsertTop = sqlite3VdbeMakeLabel(v);
      sAddr.upsertBtm = sqlite3VdbeMakeLabel(v);
    }
  }

  /* If rowid is changing, make sure the new rowid does not previously
  ** exist in the table.
  */
  if( pkChng && pPk==0 ){
    int addrRowidOk = sqlite3VdbeMakeLabel(v);

      ** is unchanged. */
      sqlite3VdbeAddOp3(v, OP_Eq, regNewData, addrRowidOk, regOldData);
      sqlite3VdbeChangeP5(v, SQLITE_NOTNULL);
      VdbeCoverage(v);
    }

    /* figure out whether or not upsert applies in this case */
    if( pUpsert && pUpsert->pUpsertIdx==0 ){
      if( pUpsert->pUpsertSet==0 ){
        onError = OE_Ignore;  /* DO NOTHING is the same as INSERT OR IGNORE */
      }else{
        onError = OE_Update;  /* DO UPDATE */
      }
    }

    /* If the response to a rowid conflict is REPLACE but the response
    ** to some other UNIQUE constraint is FAIL or IGNORE, then we need
    ** to defer the running of the rowid conflict checking until after
    ** the UNIQUE constraints have run.
    */
    assert( OE_Update>OE_Replace );
    assert( OE_Ignore<OE_Replace );
    assert( OE_Fail<OE_Replace );
    assert( OE_Abort<OE_Replace );
    assert( OE_Rollback<OE_Replace );
    if( onError>=OE_Replace
     && onError!=overrideError
     && pTab->pIndex

    ){
      sAddr.ipkTop = sqlite3VdbeAddOp0(v, OP_Goto)+1;



    }

    /* Check to see if the new rowid already exists in the table.  Skip
    ** the following conflict logic if it does not. */
    VdbeNoopComment((v, "constraint checks for ROWID"));
    sqlite3VdbeAddOp3(v, OP_NotExists, iDataCur, addrRowidOk, regNewData);
    VdbeCoverage(v);

    switch( onError ){
      default: {
        onError = OE_Abort;
        /* Fall thru into the next case */

#endif
      case OE_Ignore: {
        sqlite3VdbeGoto(v, ignoreDest);
        break;
      }
    }
    sqlite3VdbeResolveLabel(v, addrRowidOk);
    if( sAddr.ipkTop ){
      sAddr.ipkBtm = sqlite3VdbeAddOp0(v, OP_Goto);
      sqlite3VdbeJumpHere(v, sAddr.ipkTop-1);
    }
  }

  /* Test all UNIQUE constraints by creating entries for each UNIQUE
  ** index and making sure that duplicate entries do not already exist.
  ** Compute the revised record entries for indices as we go.
  **
  ** This loop also handles the case of the PRIMARY KEY index for a
  ** WITHOUT ROWID table.
  */
  for(ix=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, ix++){
    int regIdx;          /* Range of registers hold conent for pIdx */
    int regR;            /* Range of registers holding conflicting PK */
    int iThisCur;        /* Cursor for this UNIQUE index */
    int addrUniqueOk;    /* Jump here if the UNIQUE constraint is satisfied */

    if( aRegIdx[ix]==0 ) continue;  /* Skip indices that do not change */
    VdbeNoopComment((v, "constraint checks for %s", pIdx->zName));
    if( bAffinityDone==0 ){
      sqlite3TableAffinity(v, pTab, regNewData+1);
      bAffinityDone = 1;
    }
    iThisCur = iIdxCur+ix;
    if( pUpIdx==pIdx ){
      addrUniqueOk = sAddr.upsertBtm;
    }else{
      addrUniqueOk = sqlite3VdbeMakeLabel(v);
    }

    /* Skip partial indices for which the WHERE clause is not true */
    if( pIdx->pPartIdxWhere ){
      sqlite3VdbeAddOp2(v, OP_Null, 0, aRegIdx[ix]);
      pParse->iSelfTab = -(regNewData+1);
      sqlite3ExprIfFalseDup(pParse, pIdx->pPartIdxWhere, addrUniqueOk,
                            SQLITE_JUMPIFNULL);

      continue;  /* pIdx is not a UNIQUE index */
    }
    if( overrideError!=OE_Default ){
      onError = overrideError;
    }else if( onError==OE_Default ){
      onError = OE_Abort;
    }
    if( onError==OE_Replace ){
      reorderConstraintChecks(v, &sAddr);
    }

    /* Figure out if the upsert clause applies to this index */
    if( pUpIdx==pIdx ){
      if( pUpsert->pUpsertSet==0 ){
        onError = OE_Ignore;  /* DO NOTHING is the same as INSERT OR IGNORE */
      }else{
        onError = OE_Update;  /* DO UPDATE */
      }
      upsertBypass = sqlite3VdbeGoto(v, 0);
      VdbeComment((v, "Upsert bypass"));
      sqlite3VdbeResolveLabel(v, sAddr.upsertTop);
    }

    /* Collision detection may be omitted if all of the following are true:
    **   (1) The conflict resolution algorithm is REPLACE
    **   (2) The table is a WITHOUT ROWID table
    **   (3) There are no secondary indexes on the table
    **   (4) No delete triggers need to be fired if there is a conflict

        seenReplace = 1;
        break;
      }
    }
    sqlite3VdbeResolveLabel(v, addrUniqueOk);
    sqlite3ExprCachePop(pParse);
    if( regR!=regIdx ) sqlite3ReleaseTempRange(pParse, regR, nPkField);
    if( pUpIdx==pIdx ) sqlite3VdbeJumpHere(v, upsertBypass);




  }
  reorderConstraintChecks(v, &sAddr);
  
  *pbMayReplace = seenReplace;
  VdbeModuleComment((v, "END: GenCnstCks(%d)", seenReplace));
}

#ifdef SQLITE_ENABLE_NULL_TRIM
/*