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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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| Downloads: | Tarball | ZIP archive | SQL archive |
| Timelines: | family | ancestors | descendants | both | trunk |
| Files: | files | file ages | folders |
| SHA1: | a29e117d7ecec05da949348689dbfb0d3acb1280 |
| User & Date: | drh 2015-05-29 01:35:19 |
References
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2017-09-28
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| 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: ff2f5a31 user: drh tags: trunk | |
Context
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2015-05-29
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| 14:47 | Add support for automatic indexes on FROM-clause subqueries that are implemented via co-routine. check-in: 020b8b10 user: drh tags: trunk | |
| 13:55 | An attempt to allow automatic index creation on subqueries accessed via co-routine. check-in: 521345ad 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: a29e117d user: drh tags: trunk | |
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2015-05-28
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| 15:14 | Added comments and testcase() macros to error cases in the btree search. check-in: 7da7dc71 user: drh tags: trunk | |
Changes
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.
//
................................................................................
%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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}
// 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.
//
................................................................................
%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;
|
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". ** |