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Overview
Comment:Using "SELECT ALL" instead of just "SELECT" on a query that uses a single unflattenable subquery or view in its FROM clause will force the subquery to be manifested into a temporary table rather than run incrementally using a co-routine. This is a stop-gap means of controlling the decision to manifest while we try to work out a better to make that decision automatically.
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SHA1: a29e117d7ecec05da949348689dbfb0d3acb1280
User & Date: drh 2015-05-29 01:35:19.289
References
2017-09-28
17:29
Remove the (undocumented) query-planner control that prevents a "SELECT ALL" subquery in FROM clause from being implemented as a co-routine. This control was added by [a29e117d7ec], where it was called a "stop-gap". (check-in: ff2f5a31a2 user: drh tags: trunk)
Context
2015-05-29
14:47
Add support for automatic indexes on FROM-clause subqueries that are implemented via co-routine. (check-in: 020b8b106f user: drh tags: trunk)
13:55
An attempt to allow automatic index creation on subqueries accessed via co-routine. (check-in: 521345add6 user: drh tags: coroutine-autoindex)
01:35
Using "SELECT ALL" instead of just "SELECT" on a query that uses a single unflattenable subquery or view in its FROM clause will force the subquery to be manifested into a temporary table rather than run incrementally using a co-routine. This is a stop-gap means of controlling the decision to manifest while we try to work out a better to make that decision automatically. (check-in: a29e117d7e user: drh tags: trunk)
2015-05-28
15:14
Added comments and testcase() macros to error cases in the btree search. (check-in: 7da7dc714b user: drh tags: trunk)
Changes
Unified Diff Ignore Whitespace Patch
Changes to src/parse.y.
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}

// The "distinct" nonterminal is true (1) if the DISTINCT keyword is
// present and false (0) if it is not.
//
%type distinct {u16}
distinct(A) ::= DISTINCT.   {A = SF_Distinct;}
distinct(A) ::= ALL.        {A = 0;}
distinct(A) ::= .           {A = 0;}

// selcollist is a list of expressions that are to become the return
// values of the SELECT statement.  The "*" in statements like
// "SELECT * FROM ..." is encoded as a special expression with an
// opcode of TK_ALL.
//








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}

// The "distinct" nonterminal is true (1) if the DISTINCT keyword is
// present and false (0) if it is not.
//
%type distinct {u16}
distinct(A) ::= DISTINCT.   {A = SF_Distinct;}
distinct(A) ::= ALL.        {A = SF_All;}
distinct(A) ::= .           {A = 0;}

// selcollist is a list of expressions that are to become the return
// values of the SELECT statement.  The "*" in statements like
// "SELECT * FROM ..." is encoded as a special expression with an
// opcode of TK_ALL.
//
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%endif  SQLITE_OMIT_CAST
expr(A) ::= id(X) LP distinct(D) exprlist(Y) RP(E). {
  if( Y && Y->nExpr>pParse->db->aLimit[SQLITE_LIMIT_FUNCTION_ARG] ){
    sqlite3ErrorMsg(pParse, "too many arguments on function %T", &X);
  }
  A.pExpr = sqlite3ExprFunction(pParse, Y, &X);
  spanSet(&A,&X,&E);
  if( D && A.pExpr ){
    A.pExpr->flags |= EP_Distinct;
  }
}
expr(A) ::= id(X) LP STAR RP(E). {
  A.pExpr = sqlite3ExprFunction(pParse, 0, &X);
  spanSet(&A,&X,&E);
}








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%endif  SQLITE_OMIT_CAST
expr(A) ::= id(X) LP distinct(D) exprlist(Y) RP(E). {
  if( Y && Y->nExpr>pParse->db->aLimit[SQLITE_LIMIT_FUNCTION_ARG] ){
    sqlite3ErrorMsg(pParse, "too many arguments on function %T", &X);
  }
  A.pExpr = sqlite3ExprFunction(pParse, Y, &X);
  spanSet(&A,&X,&E);
  if( D==SF_Distinct && A.pExpr ){
    A.pExpr->flags |= EP_Distinct;
  }
}
expr(A) ::= id(X) LP STAR RP(E). {
  A.pExpr = sqlite3ExprFunction(pParse, 0, &X);
  spanSet(&A,&X,&E);
}
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Changes to src/select.c.
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      /* This subquery can be absorbed into its parent. */
      if( isAggSub ){
        isAgg = 1;
        p->selFlags |= SF_Aggregate;
      }
      i = -1;
    }else if( pTabList->nSrc==1

           && OptimizationEnabled(db, SQLITE_SubqCoroutine)
    ){
      /* Implement a co-routine that will return a single row of the result
      ** set on each invocation.
      */
      int addrTop = sqlite3VdbeCurrentAddr(v)+1;
      pItem->regReturn = ++pParse->nMem;








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      /* This subquery can be absorbed into its parent. */
      if( isAggSub ){
        isAgg = 1;
        p->selFlags |= SF_Aggregate;
      }
      i = -1;
    }else if( pTabList->nSrc==1
           && (p->selFlags & SF_All)==0
           && OptimizationEnabled(db, SQLITE_SubqCoroutine)
    ){
      /* Implement a co-routine that will return a single row of the result
      ** set on each invocation.
      */
      int addrTop = sqlite3VdbeCurrentAddr(v)+1;
      pItem->regReturn = ++pParse->nMem;
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Changes to src/sqliteInt.h.
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};

/*
** Allowed values for Select.selFlags.  The "SF" prefix stands for
** "Select Flag".
*/
#define SF_Distinct        0x0001  /* Output should be DISTINCT */

#define SF_Resolved        0x0002  /* Identifiers have been resolved */
#define SF_Aggregate       0x0004  /* Contains aggregate functions */
#define SF_UsesEphemeral   0x0008  /* Uses the OpenEphemeral opcode */
#define SF_Expanded        0x0010  /* sqlite3SelectExpand() called on this */
#define SF_HasTypeInfo     0x0020  /* FROM subqueries have Table metadata */
#define SF_Compound        0x0040  /* Part of a compound query */
#define SF_Values          0x0080  /* Synthesized from VALUES clause */
#define SF_MultiValue      0x0100  /* Single VALUES term with multiple rows */
#define SF_NestedFrom      0x0200  /* Part of a parenthesized FROM clause */
#define SF_MaybeConvert    0x0400  /* Need convertCompoundSelectToSubquery() */
#define SF_Recursive       0x0800  /* The recursive part of a recursive CTE */
#define SF_MinMaxAgg       0x1000  /* Aggregate containing min() or max() */

#define SF_Converted       0x2000  /* By convertCompoundSelectToSubquery() */


/*
** The results of a SELECT can be distributed in several ways, as defined
** by one of the following macros.  The "SRT" prefix means "SELECT Result
** Type".
**








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};

/*
** Allowed values for Select.selFlags.  The "SF" prefix stands for
** "Select Flag".
*/
#define SF_Distinct        0x0001  /* Output should be DISTINCT */
#define SF_All             0x0002  /* Includes the ALL keyword */
#define SF_Resolved        0x0004  /* Identifiers have been resolved */
#define SF_Aggregate       0x0008  /* Contains aggregate functions */
#define SF_UsesEphemeral   0x0010  /* Uses the OpenEphemeral opcode */
#define SF_Expanded        0x0020  /* sqlite3SelectExpand() called on this */
#define SF_HasTypeInfo     0x0040  /* FROM subqueries have Table metadata */
#define SF_Compound        0x0080  /* Part of a compound query */
#define SF_Values          0x0100  /* Synthesized from VALUES clause */
#define SF_MultiValue      0x0200  /* Single VALUES term with multiple rows */
#define SF_NestedFrom      0x0400  /* Part of a parenthesized FROM clause */
#define SF_MaybeConvert    0x0800  /* Need convertCompoundSelectToSubquery() */

#define SF_MinMaxAgg       0x1000  /* Aggregate containing min() or max() */
#define SF_Recursive       0x2000  /* The recursive part of a recursive CTE */
#define SF_Converted       0x4000  /* By convertCompoundSelectToSubquery() */


/*
** The results of a SELECT can be distributed in several ways, as defined
** by one of the following macros.  The "SRT" prefix means "SELECT Result
** Type".
**
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