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Overview
Comment:In UPDATE processing, include generated columns in the set of columns being updated if and only if their generator expressions reference some other column that is being updated.
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SHA3-256: d38176e93a628e03f1bd8b689fbc4152a1495388da917c2d89cefed04353d2d6
User & Date: drh 2019-10-22 13:59:23
Context
2019-10-22
15:45
Do not allow generated columns in the PRIMARY KEY. check-in: 1a54743a user: drh tags: generated-columns
13:59
In UPDATE processing, include generated columns in the set of columns being updated if and only if their generator expressions reference some other column that is being updated. check-in: d38176e9 user: drh tags: generated-columns
13:01
New testcase() macros. Fix a problem with INSERT when the IPK is to the right of generated columns. check-in: 412799fc user: drh tags: generated-columns
Changes
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Changes to src/build.c.

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  sqlite3 *db = pParse->db;
  p = pParse->pNewTable;
  if( p!=0 ){
    pCol = &(p->aCol[p->nCol-1]);
    if( !sqlite3ExprIsConstantOrFunction(pExpr, db->init.busy) ){
      sqlite3ErrorMsg(pParse, "default value of column [%s] is not constant",
          pCol->zName);






    }else{
      /* A copy of pExpr is used instead of the original, as pExpr contains
      ** tokens that point to volatile memory.
      */
      Expr x;
      sqlite3ExprDelete(db, pCol->pDflt);
      memset(&x, 0, sizeof(x));
................................................................................
  assert( TF_HasStored==COLFLAG_STORED );
  pTab->tabFlags |= eType;
  pCol->pDflt = pExpr;
  pExpr = 0;
  goto generated_done;

generated_error:
  sqlite3ErrorMsg(pParse, "incorrect GENERATED ALWAYS AS on column \"%s\"",
                  pCol->zName);
generated_done:
  sqlite3ExprDelete(pParse->db, pExpr);
#else
  /* Throw and error for the GENERATED ALWAYS AS clause if the
  ** SQLITE_OMIT_GENERATED_COLUMNS compile-time option is used. */
  sqlite3ErrorMsg(pParse, "GENERATED ALWAYS AS not supported");
  sqlite3ExprDelete(pParse->db, pExpr);
#endif
}

/*
** Generate code that will increment the schema cookie.
**







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  sqlite3 *db = pParse->db;
  p = pParse->pNewTable;
  if( p!=0 ){
    pCol = &(p->aCol[p->nCol-1]);
    if( !sqlite3ExprIsConstantOrFunction(pExpr, db->init.busy) ){
      sqlite3ErrorMsg(pParse, "default value of column [%s] is not constant",
          pCol->zName);
#ifndef SQLITE_OMIT_GENERATED_COLUMNS
    }else if( pCol->colFlags & COLFLAG_GENERATED ){
      testcase( pCol->colflags & COLFLAG_VIRTUAL );
      testcase( pCol->colflags & COLFLAG_STORED );
      sqlite3ErrorMsg(pParse, "cannot use DEFAULT on a generated column");
#endif
    }else{
      /* A copy of pExpr is used instead of the original, as pExpr contains
      ** tokens that point to volatile memory.
      */
      Expr x;
      sqlite3ExprDelete(db, pCol->pDflt);
      memset(&x, 0, sizeof(x));
................................................................................
  assert( TF_HasStored==COLFLAG_STORED );
  pTab->tabFlags |= eType;
  pCol->pDflt = pExpr;
  pExpr = 0;
  goto generated_done;

generated_error:
  sqlite3ErrorMsg(pParse, "error in generated column \"%s\"",
                  pCol->zName);
generated_done:
  sqlite3ExprDelete(pParse->db, pExpr);
#else
  /* Throw and error for the GENERATED ALWAYS AS clause if the
  ** SQLITE_OMIT_GENERATED_COLUMNS compile-time option is used. */
  sqlite3ErrorMsg(pParse, "generated columns not supported");
  sqlite3ExprDelete(pParse->db, pExpr);
#endif
}

/*
** Generate code that will increment the schema cookie.
**

Changes to src/update.c.

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    }
#endif
  }
  assert( (chngRowid & chngPk)==0 );
  assert( chngRowid==0 || chngRowid==1 );
  assert( chngPk==0 || chngPk==1 );
  chngKey = chngRowid + chngPk;




























  /* The SET expressions are not actually used inside the WHERE loop.  
  ** So reset the colUsed mask. Unless this is a virtual table. In that
  ** case, set all bits of the colUsed mask (to ensure that the virtual
  ** table implementation makes all columns available).
  */
  pTabList->a[0].colUsed = IsVirtual(pTab) ? ALLBITS : 0;
................................................................................

  /* Start scanning the virtual table */
  pWInfo = sqlite3WhereBegin(pParse, pSrc, pWhere, 0,0,WHERE_ONEPASS_DESIRED,0);
  if( pWInfo==0 ) return;

  /* Populate the argument registers. */
  for(i=0; i<pTab->nCol; i++){

    if( aXRef[i]>=0 ){
      sqlite3ExprCode(pParse, pChanges->a[aXRef[i]].pExpr, regArg+2+i);
    }else{
      sqlite3VdbeAddOp3(v, OP_VColumn, iCsr, i, regArg+2+i);
      sqlite3VdbeChangeP5(v, OPFLAG_NOCHNG);/* Enable sqlite3_vtab_nochange() */
    }
  }







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    }
#endif
  }
  assert( (chngRowid & chngPk)==0 );
  assert( chngRowid==0 || chngRowid==1 );
  assert( chngPk==0 || chngPk==1 );
  chngKey = chngRowid + chngPk;

#ifndef SQLITE_OMIT_GENERATED_COLUMNS
  /* Mark generated columns as changing if their generator expressions
  ** reference any changing column.  The actual aXRef[] value for 
  ** generated expressions is not used, other than to check to see that it
  ** is non-negative, so the value of aXRef[] for generated columns can be
  ** set to any non-negative number.  We use 99999 so that the value is
  ** obvious when looking at aXRef[] in a symbolic debugger. 
  */
  if( pTab->tabFlags & TF_HasGenerated ){
    int bProgress;
    testcase( pTab->tabFlags & TF_HasVirtual );
    testcase( pTab->tabFlags & TF_HasStored );
    do{
      bProgress = 0;
      for(i=0; i<pTab->nCol; i++){
        if( aXRef[i]>=0 ) continue;
        if( (pTab->aCol[i].colFlags & COLFLAG_GENERATED)==0 ) continue;
        if( sqlite3ExprReferencesUpdatedColumn(pTab->aCol[i].pDflt,
                                               aXRef, chngRowid) ){
          aXRef[i] = 99999;
          bProgress = 1;
        }
      }
    }while( bProgress );
  }
#endif

  /* The SET expressions are not actually used inside the WHERE loop.  
  ** So reset the colUsed mask. Unless this is a virtual table. In that
  ** case, set all bits of the colUsed mask (to ensure that the virtual
  ** table implementation makes all columns available).
  */
  pTabList->a[0].colUsed = IsVirtual(pTab) ? ALLBITS : 0;
................................................................................

  /* Start scanning the virtual table */
  pWInfo = sqlite3WhereBegin(pParse, pSrc, pWhere, 0,0,WHERE_ONEPASS_DESIRED,0);
  if( pWInfo==0 ) return;

  /* Populate the argument registers. */
  for(i=0; i<pTab->nCol; i++){
    assert( (pTab->aCol[i].colFlags & COLFLAG_GENERATED)==0 );
    if( aXRef[i]>=0 ){
      sqlite3ExprCode(pParse, pChanges->a[aXRef[i]].pExpr, regArg+2+i);
    }else{
      sqlite3VdbeAddOp3(v, OP_VColumn, iCsr, i, regArg+2+i);
      sqlite3VdbeChangeP5(v, OPFLAG_NOCHNG);/* Enable sqlite3_vtab_nochange() */
    }
  }