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Overview
Comment:Move the generation of output column names earlier, to right after name resolution and before query transformations such as flattening. This prevents the names from getting mangled by query transformations, and obviates hacks in the query flattener that attempt to work around the name mangling. The resulting code is smaller and faster and gives more consistent output. This is a fix for ticket [de3403bf5ae5f72ed] and a cherry-pick of check-in [09834279aeca3bda]
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SHA3-256:499942b3eece097a6b1695ebe60d7eb3d7f3de397bc28ebf6b1fe038116487e8
User & Date: drh 2017-07-31 13:11:26
Context
2017-07-31
13:22
Use batch atomic writes when running on a recent F2FS filesystem, if compiled with SQLITE_ENABLE_BATCH_ATOMIC_WRITE. check-in: 2dd0c77d user: drh tags: branch-3.19
13:11
Move the generation of output column names earlier, to right after name resolution and before query transformations such as flattening. This prevents the names from getting mangled by query transformations, and obviates hacks in the query flattener that attempt to work around the name mangling. The resulting code is smaller and faster and gives more consistent output. This is a fix for ticket [de3403bf5ae5f72ed] and a cherry-pick of check-in [09834279aeca3bda] check-in: 499942b3 user: drh tags: branch-3.19
12:19
Correctly handle an "INTEGER PRIMARY KEY UNIQUE" column in a WITHOUT ROWID table. This is a fix for ticket [bc115541132dad136], cherry-picked from check-in [5216bfb73f1a49bdd8] check-in: 322a2ede user: drh tags: branch-3.19
2017-07-29
16:01
Move the generation of output column names earlier, to right after name resolution and before query transformations such as flattening. This prevents the names from getting mangled by query transformations, and obviates hacks in the query flattener that attempt to work around the name mangling. The resulting code is smaller and faster and gives more consistent output. This is an alternative fix to ticket [de3403bf5ae5f72ed]. check-in: 09834279 user: drh tags: early-column-names
Changes
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Changes to src/select.c.

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      assert( pTab && pExpr->pTab==pTab );
      if( pS ){
        /* The "table" is actually a sub-select or a view in the FROM clause
        ** of the SELECT statement. Return the declaration type and origin
        ** data for the result-set column of the sub-select.
        */
        if( iCol>=0 && ALWAYS(iCol<pS->pEList->nExpr) ){
          /* If iCol is less than zero, then the expression requests the
          ** rowid of the sub-select or view. This expression is legal (see 
          ** test case misc2.2.2) - it always evaluates to NULL.
          **
          ** The ALWAYS() is because iCol>=pS->pEList->nExpr will have been
          ** caught already by name resolution.
          */
          NameContext sNC;
          Expr *p = pS->pEList->a[iCol].pExpr;
          sNC.pSrcList = pS->pSrc;
          sNC.pNext = pNC;
          sNC.pParse = pNC->pParse;
          zType = columnType(&sNC, p,&zOrigDb,&zOrigTab,&zOrigCol, &estWidth); 
................................................................................
    zType = columnType(&sNC, p, 0, 0, 0, 0);
#endif
    sqlite3VdbeSetColName(v, i, COLNAME_DECLTYPE, zType, SQLITE_TRANSIENT);
  }
#endif /* !defined(SQLITE_OMIT_DECLTYPE) */
}

/*
** Return the Table objecct in the SrcList that has cursor iCursor.
** Or return NULL if no such Table object exists in the SrcList.
*/
static Table *tableWithCursor(SrcList *pList, int iCursor){
  int j;
  for(j=0; j<pList->nSrc; j++){
    if( pList->a[j].iCursor==iCursor ) return pList->a[j].pTab;
  }
  return 0;
}


/*
** Generate code that will tell the VDBE the names of columns
** in the result set.  This information is used to provide the
** azCol[] values in the callback.
*/
static void generateColumnNames(
  Parse *pParse,      /* Parser context */
  SrcList *pTabList,  /* List of tables */
  ExprList *pEList    /* Expressions defining the result set */
){
  Vdbe *v = pParse->pVdbe;
  int i;
  Table *pTab;


  sqlite3 *db = pParse->db;
  int fullNames, shortNames;



#ifndef SQLITE_OMIT_EXPLAIN
  /* If this is an EXPLAIN, skip this step */
  if( pParse->explain ){
    return;
  }
#endif

  if( pParse->colNamesSet || db->mallocFailed ) return;




  assert( v!=0 );
  assert( pTabList!=0 );
  pParse->colNamesSet = 1;
  fullNames = (db->flags & SQLITE_FullColNames)!=0;
  shortNames = (db->flags & SQLITE_ShortColNames)!=0;
  sqlite3VdbeSetNumCols(v, pEList->nExpr);
  for(i=0; i<pEList->nExpr; i++){
    Expr *p;
    p = pEList->a[i].pExpr;

    if( NEVER(p==0) ) continue;
    if( pEList->a[i].zName ){

      char *zName = pEList->a[i].zName;
      sqlite3VdbeSetColName(v, i, COLNAME_NAME, zName, SQLITE_TRANSIENT);
    }else if( (p->op==TK_COLUMN || p->op==TK_AGG_COLUMN)
           && (pTab = tableWithCursor(pTabList, p->iTable))!=0
    ){
      char *zCol;
      int iCol = p->iColumn;


      if( iCol<0 ) iCol = pTab->iPKey;
      assert( iCol==-1 || (iCol>=0 && iCol<pTab->nCol) );
      if( iCol<0 ){
        zCol = "rowid";
      }else{
        zCol = pTab->aCol[iCol].zName;
      }
      if( !shortNames && !fullNames ){
        sqlite3VdbeSetColName(v, i, COLNAME_NAME, 
            sqlite3DbStrDup(db, pEList->a[i].zSpan), SQLITE_DYNAMIC);
      }else if( fullNames ){
        char *zName = 0;
        zName = sqlite3MPrintf(db, "%s.%s", pTab->zName, zCol);
        sqlite3VdbeSetColName(v, i, COLNAME_NAME, zName, SQLITE_DYNAMIC);
      }else{
        sqlite3VdbeSetColName(v, i, COLNAME_NAME, zCol, SQLITE_TRANSIENT);
      }
    }else{
................................................................................
      /* Convert the data in the temporary table into whatever form
      ** it is that we currently need.
      */
      assert( unionTab==dest.iSDParm || dest.eDest!=priorOp );
      if( dest.eDest!=priorOp ){
        int iCont, iBreak, iStart;
        assert( p->pEList );
        if( dest.eDest==SRT_Output ){
          Select *pFirst = p;
          while( pFirst->pPrior ) pFirst = pFirst->pPrior;
          generateColumnNames(pParse, pFirst->pSrc, pFirst->pEList);
        }
        iBreak = sqlite3VdbeMakeLabel(v);
        iCont = sqlite3VdbeMakeLabel(v);
        computeLimitRegisters(pParse, p, iBreak);
        sqlite3VdbeAddOp2(v, OP_Rewind, unionTab, iBreak); VdbeCoverage(v);
        iStart = sqlite3VdbeCurrentAddr(v);
        selectInnerLoop(pParse, p, p->pEList, unionTab,
                        0, 0, &dest, iCont, iBreak);
................................................................................
      p->pLimit = pLimit;
      p->pOffset = pOffset;

      /* Generate code to take the intersection of the two temporary
      ** tables.
      */
      assert( p->pEList );
      if( dest.eDest==SRT_Output ){
        Select *pFirst = p;
        while( pFirst->pPrior ) pFirst = pFirst->pPrior;
        generateColumnNames(pParse, pFirst->pSrc, pFirst->pEList);
      }
      iBreak = sqlite3VdbeMakeLabel(v);
      iCont = sqlite3VdbeMakeLabel(v);
      computeLimitRegisters(pParse, p, iBreak);
      sqlite3VdbeAddOp2(v, OP_Rewind, tab1, iBreak); VdbeCoverage(v);
      r1 = sqlite3GetTempReg(pParse);
      iStart = sqlite3VdbeAddOp2(v, OP_RowData, tab1, r1);
      sqlite3VdbeAddOp4Int(v, OP_NotFound, tab2, iCont, r1, 0); VdbeCoverage(v);
................................................................................
  sqlite3VdbeChangeP5(v, OPFLAG_PERMUTE);
  sqlite3VdbeAddOp3(v, OP_Jump, addrAltB, addrAeqB, addrAgtB); VdbeCoverage(v);

  /* Jump to the this point in order to terminate the query.
  */
  sqlite3VdbeResolveLabel(v, labelEnd);

  /* Set the number of output columns
  */
  if( pDest->eDest==SRT_Output ){
    Select *pFirst = pPrior;
    while( pFirst->pPrior ) pFirst = pFirst->pPrior;
    generateColumnNames(pParse, pFirst->pSrc, pFirst->pEList);
  }

  /* Reassembly the compound query so that it will be freed correctly
  ** by the calling function */
  if( p->pPrior ){
    sqlite3SelectDelete(db, p->pPrior);
  }
  p->pPrior = pPrior;
  pPrior->pNext = p;
................................................................................
){
  const char *zSavedAuthContext = pParse->zAuthContext;
  Select *pParent;    /* Current UNION ALL term of the other query */
  Select *pSub;       /* The inner query or "subquery" */
  Select *pSub1;      /* Pointer to the rightmost select in sub-query */
  SrcList *pSrc;      /* The FROM clause of the outer query */
  SrcList *pSubSrc;   /* The FROM clause of the subquery */
  ExprList *pList;    /* The result set of the outer query */
  int iParent;        /* VDBE cursor number of the pSub result set temp table */
  int iNewParent = -1;/* Replacement table for iParent */
  int isLeftJoin = 0; /* True if pSub is the right side of a LEFT JOIN */    
  int i;              /* Loop counter */
  Expr *pWhere;                    /* The WHERE clause */
  struct SrcList_item *pSubitem;   /* The subquery */
  sqlite3 *db = pParse->db;
................................................................................
    **   SELECT a+5, b*10 FROM (SELECT x*3 AS a, y+10 AS b FROM t1) WHERE a>b;
    **   \                     \_____________ subquery __________/          /
    **    \_____________________ outer query ______________________________/
    **
    ** We look at every expression in the outer query and every place we see
    ** "a" we substitute "x*3" and every place we see "b" we substitute "y+10".
    */
    pList = pParent->pEList;
    for(i=0; i<pList->nExpr; i++){
      if( pList->a[i].zName==0 ){
        char *zName = sqlite3DbStrDup(db, pList->a[i].zSpan);
        sqlite3Dequote(zName);
        pList->a[i].zName = zName;
      }
    }
    if( pSub->pOrderBy ){
      /* At this point, any non-zero iOrderByCol values indicate that the
      ** ORDER BY column expression is identical to the iOrderByCol'th
      ** expression returned by SELECT statement pSub. Since these values
      ** do not necessarily correspond to columns in SELECT statement pParent,
      ** zero them before transfering the ORDER BY clause.
      **
................................................................................
  isAgg = (p->selFlags & SF_Aggregate)!=0;
#if SELECTTRACE_ENABLED
  if( sqlite3SelectTrace & 0x100 ){
    SELECTTRACE(0x100,pParse,p, ("after name resolution:\n"));
    sqlite3TreeViewSelect(0, p, 0);
  }
#endif









  /* Try to flatten subqueries in the FROM clause up into the main query
  */
#if !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW)
  for(i=0; !p->pPrior && i<pTabList->nSrc; i++){
    struct SrcList_item *pItem = &pTabList->a[i];
    Select *pSub = pItem->pSelect;
................................................................................
    if( db->mallocFailed ) goto select_end;
    if( !IgnorableOrderby(pDest) ){
      sSort.pOrderBy = p->pOrderBy;
    }
  }
#endif

  /* Get a pointer the VDBE under construction, allocating a new VDBE if one
  ** does not already exist */
  v = sqlite3GetVdbe(pParse);
  if( v==0 ) goto select_end;

#ifndef SQLITE_OMIT_COMPOUND_SELECT
  /* Handle compound SELECT statements using the separate multiSelect()
  ** procedure.
  */
  if( p->pPrior ){
    rc = multiSelect(pParse, p, pDest);
    explainSetInteger(pParse->iSelectId, iRestoreSelectId);
................................................................................

  /* Control jumps to here if an error is encountered above, or upon
  ** successful coding of the SELECT.
  */
select_end:
  explainSetInteger(pParse->iSelectId, iRestoreSelectId);

  /* Identify column names if results of the SELECT are to be output.
  */
  if( rc==SQLITE_OK && pDest->eDest==SRT_Output ){
    generateColumnNames(pParse, pTabList, pEList);
  }

  sqlite3DbFree(db, sAggInfo.aCol);
  sqlite3DbFree(db, sAggInfo.aFunc);
#if SELECTTRACE_ENABLED
  SELECTTRACE(1,pParse,p,("end processing\n"));
  pParse->nSelectIndent--;
#endif
  return rc;
}







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      assert( pTab && pExpr->pTab==pTab );
      if( pS ){
        /* The "table" is actually a sub-select or a view in the FROM clause
        ** of the SELECT statement. Return the declaration type and origin
        ** data for the result-set column of the sub-select.
        */
        if( iCol>=0 && iCol<pS->pEList->nExpr ){
          /* If iCol is less than zero, then the expression requests the
          ** rowid of the sub-select or view. This expression is legal (see 
          ** test case misc2.2.2) - it always evaluates to NULL.



          */
          NameContext sNC;
          Expr *p = pS->pEList->a[iCol].pExpr;
          sNC.pSrcList = pS->pSrc;
          sNC.pNext = pNC;
          sNC.pParse = pNC->pParse;
          zType = columnType(&sNC, p,&zOrigDb,&zOrigTab,&zOrigCol, &estWidth); 
................................................................................
    zType = columnType(&sNC, p, 0, 0, 0, 0);
#endif
    sqlite3VdbeSetColName(v, i, COLNAME_DECLTYPE, zType, SQLITE_TRANSIENT);
  }
#endif /* !defined(SQLITE_OMIT_DECLTYPE) */
}














/*
** Generate code that will tell the VDBE the names of columns
** in the result set.  This information is used to provide the
** azCol[] values in the callback.
*/
static void generateColumnNames(
  Parse *pParse,      /* Parser context */
  Select *pSelect     /* Generate column names for this SELECT statement */

){
  Vdbe *v = pParse->pVdbe;
  int i;
  Table *pTab;
  SrcList *pTabList;
  ExprList *pEList;
  sqlite3 *db = pParse->db;

  int fullName;    /* TABLE.COLUMN if no AS clause and is a direct table ref */
  int srcName;     /* COLUMN or TABLE.COLUMN if no AS clause and is direct */

#ifndef SQLITE_OMIT_EXPLAIN
  /* If this is an EXPLAIN, skip this step */
  if( pParse->explain ){
    return;
  }
#endif

  if( pParse->colNamesSet || db->mallocFailed ) return;
  /* Column names are determined by the left-most term of a compound select */
  while( pSelect->pPrior ) pSelect = pSelect->pPrior;
  pTabList = pSelect->pSrc;
  pEList = pSelect->pEList;
  assert( v!=0 );
  assert( pTabList!=0 );
  pParse->colNamesSet = 1;
  fullName = (db->flags & SQLITE_FullColNames)!=0;
  srcName = (db->flags & SQLITE_ShortColNames)!=0 || fullName;
  sqlite3VdbeSetNumCols(v, pEList->nExpr);
  for(i=0; i<pEList->nExpr; i++){

    Expr *p = pEList->a[i].pExpr;

    assert( p!=0 );
    if( pEList->a[i].zName ){
      /* An AS clause always takes first priority */
      char *zName = pEList->a[i].zName;
      sqlite3VdbeSetColName(v, i, COLNAME_NAME, zName, SQLITE_TRANSIENT);
    }else if( srcName && p->op==TK_COLUMN ){


      char *zCol;
      int iCol = p->iColumn;
      pTab = p->pTab;
      assert( pTab!=0 );
      if( iCol<0 ) iCol = pTab->iPKey;
      assert( iCol==-1 || (iCol>=0 && iCol<pTab->nCol) );
      if( iCol<0 ){
        zCol = "rowid";
      }else{
        zCol = pTab->aCol[iCol].zName;
      }



      if( fullName ){
        char *zName = 0;
        zName = sqlite3MPrintf(db, "%s.%s", pTab->zName, zCol);
        sqlite3VdbeSetColName(v, i, COLNAME_NAME, zName, SQLITE_DYNAMIC);
      }else{
        sqlite3VdbeSetColName(v, i, COLNAME_NAME, zCol, SQLITE_TRANSIENT);
      }
    }else{
................................................................................
      /* Convert the data in the temporary table into whatever form
      ** it is that we currently need.
      */
      assert( unionTab==dest.iSDParm || dest.eDest!=priorOp );
      if( dest.eDest!=priorOp ){
        int iCont, iBreak, iStart;
        assert( p->pEList );





        iBreak = sqlite3VdbeMakeLabel(v);
        iCont = sqlite3VdbeMakeLabel(v);
        computeLimitRegisters(pParse, p, iBreak);
        sqlite3VdbeAddOp2(v, OP_Rewind, unionTab, iBreak); VdbeCoverage(v);
        iStart = sqlite3VdbeCurrentAddr(v);
        selectInnerLoop(pParse, p, p->pEList, unionTab,
                        0, 0, &dest, iCont, iBreak);
................................................................................
      p->pLimit = pLimit;
      p->pOffset = pOffset;

      /* Generate code to take the intersection of the two temporary
      ** tables.
      */
      assert( p->pEList );





      iBreak = sqlite3VdbeMakeLabel(v);
      iCont = sqlite3VdbeMakeLabel(v);
      computeLimitRegisters(pParse, p, iBreak);
      sqlite3VdbeAddOp2(v, OP_Rewind, tab1, iBreak); VdbeCoverage(v);
      r1 = sqlite3GetTempReg(pParse);
      iStart = sqlite3VdbeAddOp2(v, OP_RowData, tab1, r1);
      sqlite3VdbeAddOp4Int(v, OP_NotFound, tab2, iCont, r1, 0); VdbeCoverage(v);
................................................................................
  sqlite3VdbeChangeP5(v, OPFLAG_PERMUTE);
  sqlite3VdbeAddOp3(v, OP_Jump, addrAltB, addrAeqB, addrAgtB); VdbeCoverage(v);

  /* Jump to the this point in order to terminate the query.
  */
  sqlite3VdbeResolveLabel(v, labelEnd);









  /* Reassembly the compound query so that it will be freed correctly
  ** by the calling function */
  if( p->pPrior ){
    sqlite3SelectDelete(db, p->pPrior);
  }
  p->pPrior = pPrior;
  pPrior->pNext = p;
................................................................................
){
  const char *zSavedAuthContext = pParse->zAuthContext;
  Select *pParent;    /* Current UNION ALL term of the other query */
  Select *pSub;       /* The inner query or "subquery" */
  Select *pSub1;      /* Pointer to the rightmost select in sub-query */
  SrcList *pSrc;      /* The FROM clause of the outer query */
  SrcList *pSubSrc;   /* The FROM clause of the subquery */

  int iParent;        /* VDBE cursor number of the pSub result set temp table */
  int iNewParent = -1;/* Replacement table for iParent */
  int isLeftJoin = 0; /* True if pSub is the right side of a LEFT JOIN */    
  int i;              /* Loop counter */
  Expr *pWhere;                    /* The WHERE clause */
  struct SrcList_item *pSubitem;   /* The subquery */
  sqlite3 *db = pParse->db;
................................................................................
    **   SELECT a+5, b*10 FROM (SELECT x*3 AS a, y+10 AS b FROM t1) WHERE a>b;
    **   \                     \_____________ subquery __________/          /
    **    \_____________________ outer query ______________________________/
    **
    ** We look at every expression in the outer query and every place we see
    ** "a" we substitute "x*3" and every place we see "b" we substitute "y+10".
    */








    if( pSub->pOrderBy ){
      /* At this point, any non-zero iOrderByCol values indicate that the
      ** ORDER BY column expression is identical to the iOrderByCol'th
      ** expression returned by SELECT statement pSub. Since these values
      ** do not necessarily correspond to columns in SELECT statement pParent,
      ** zero them before transfering the ORDER BY clause.
      **
................................................................................
  isAgg = (p->selFlags & SF_Aggregate)!=0;
#if SELECTTRACE_ENABLED
  if( sqlite3SelectTrace & 0x100 ){
    SELECTTRACE(0x100,pParse,p, ("after name resolution:\n"));
    sqlite3TreeViewSelect(0, p, 0);
  }
#endif

  /* Get a pointer the VDBE under construction, allocating a new VDBE if one
  ** does not already exist */
  v = sqlite3GetVdbe(pParse);
  if( v==0 ) goto select_end;
  if( pDest->eDest==SRT_Output ){
    generateColumnNames(pParse, p);
  }

  /* Try to flatten subqueries in the FROM clause up into the main query
  */
#if !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW)
  for(i=0; !p->pPrior && i<pTabList->nSrc; i++){
    struct SrcList_item *pItem = &pTabList->a[i];
    Select *pSub = pItem->pSelect;
................................................................................
    if( db->mallocFailed ) goto select_end;
    if( !IgnorableOrderby(pDest) ){
      sSort.pOrderBy = p->pOrderBy;
    }
  }
#endif






#ifndef SQLITE_OMIT_COMPOUND_SELECT
  /* Handle compound SELECT statements using the separate multiSelect()
  ** procedure.
  */
  if( p->pPrior ){
    rc = multiSelect(pParse, p, pDest);
    explainSetInteger(pParse->iSelectId, iRestoreSelectId);
................................................................................

  /* Control jumps to here if an error is encountered above, or upon
  ** successful coding of the SELECT.
  */
select_end:
  explainSetInteger(pParse->iSelectId, iRestoreSelectId);







  sqlite3DbFree(db, sAggInfo.aCol);
  sqlite3DbFree(db, sAggInfo.aFunc);
#if SELECTTRACE_ENABLED
  SELECTTRACE(1,pParse,p,("end processing\n"));
  pParse->nSelectIndent--;
#endif
  return rc;
}