SQLite

**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains C code routines that are called by the parser
** to handle UPDATE statements.
**
** $Id: update.c,v 1.150 2008/01/03 07:54:24 danielk1977 Exp $
*/
#include "sqliteInt.h"

#ifndef SQLITE_OMIT_VIRTUALTABLE
/* Forward declaration */
static void updateVirtualTable(
  Parse *pParse,       /* The parsing context */

    u8 enc = ENC(sqlite3VdbeDb(v));
    Column *pCol = &pTab->aCol[i];
    VdbeComment((v, "%s.%s", pTab->zName, pCol->zName));
    assert( i<pTab->nCol );
    sqlite3ValueFromExpr(sqlite3VdbeDb(v), pCol->pDflt, enc, 
                         pCol->affinity, &pValue);
    if( pValue ){
      sqlite3VdbeAddOp2(v, OP_DfltValue, 0, 0);
      sqlite3VdbeChangeP4(v, -1, (const char *)pValue, P4_MEM);
    }
  }
}

/*
** Process an UPDATE statement.

**
** Various scripts scan this source file in order to generate HTML
** documentation, headers files, or other derived files.  The formatting
** of the code in this file is, therefore, important.  See other comments
** in this file for details.  If in doubt, do not deviate from existing
** commenting and indentation practices when changing or adding code.
**
** $Id: vdbe.c,v 1.666 2008/01/03 07:54:24 danielk1977 Exp $
*/
#include "sqliteInt.h"
#include <ctype.h>
#include "vdbeInt.h"

/*
** The following global variable is incremented every time a cursor

  assert( (pOp->p1)<p->nCursor );
  assert( p->apCsr[pOp->p1]!=0 );
  pC = p->apCsr[pOp->p1];
  pC->nField = pOp->p2;
  break;
}

/* Opcode: Column P1 P2 P3 *
**
** Interpret the data that cursor P1 points to as a structure built using
** the MakeRecord instruction.  (See the MakeRecord opcode for additional
** information about the format of the data.)  Extract the P2-th column
** from this record.  If there are less that (P2+1) 
** values in the record, extract a NULL.
**

        goto op_column_out;
      }
      zData = sMem.z;
    }
    sqlite3VdbeSerialGet((u8*)zData, aType[p2], pDest);
    pDest->enc = encoding;
  }else{
    if( pOp[1].opcode==OP_DfltValue ){
      assert( pOp[1].p4type==P4_MEM );
      sqlite3VdbeMemShallowCopy(pDest, (Mem *)(pOp[1].p4.p), MEM_Static);
    }else{
      assert( pDest->flags==MEM_Null );
    }
  }

  /* If we dynamically allocated space to hold the data (in the
  ** sqlite3VdbeMemFromBtree() call above) then transfer control of that

  }

  /* pDest->z might be pointing to sMem.zShort[].  Fix that so that we
  ** can abandon sMem */
  rc = sqlite3VdbeMemMakeWriteable(pDest);

op_column_out:
  if( pOp[1].opcode==OP_DfltValue ){
    pc++;
  }
  break;
}

/* Opcode: DfltValue * * P4
**
** This instruction always follows an OP_Column.  This instruction
** does nothing by itself.  It is just a place holder for the default
** value for the previous OP_Column instruction.
*/
case OP_DfltValue: {       /* no-push */
  assert( 0 );
}

/* Opcode: MakeRecord P1 P2 P4
**
** Convert the top abs(P1) entries of the stack into a single entry
** suitable for use as a data record in a database table or as a key
** in an index.  The details of the format are irrelavant as long as
** the OP_Column opcode can decode the record later and as long as the
** sqlite3VdbeRecordCompare function will correctly compare two encoded