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Attempt to omit ORDER BY clauses from FROM-clause subqueries if those ORDER BY

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clauses do not affect the output.  See
[forum:/forumpost/2d76f2bcf65d256a|forum thread 2d76f2bcf65d256a] for
discussion.  This can help the query flattener in
some cases, resulting in faster query plans.  The current implemention does
not always work.

FossilOrigin-Name: ef97c3e7c3ea2cf1a4db6591328fe7ce3f1d189afc2d578159135824ec89e620
This commit is contained in:
drh
2021-07-15 19:29:43 +00:00
parent 480f5e3e6e
commit bb30123178
7 changed files with 98 additions and 57 deletions
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69
src/sqliteInt.h
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@@ -1744,6 +1744,7 @@ struct sqlite3 {
#define SQLITE_PropagateConst 0x00008000 /* The constant propagation opt */
#define SQLITE_MinMaxOpt 0x00010000 /* The min/max optimization */
#define SQLITE_SeekScan 0x00020000 /* The OP_SeekScan optimization */
#define SQLITE_OmitOrderBy 0x00040000 /* Omit pointless ORDER BY */
#define SQLITE_AllOpts 0xffffffff /* All optimizations */
/*
@@ -1823,12 +1824,13 @@ struct FuncDestructor {
** are assert() statements in the code to verify this.
**
** Value constraints (enforced via assert()):
** SQLITE_FUNC_MINMAX == NC_MinMaxAgg == SF_MinMaxAgg
** SQLITE_FUNC_LENGTH == OPFLAG_LENGTHARG
** SQLITE_FUNC_TYPEOF == OPFLAG_TYPEOFARG
** SQLITE_FUNC_CONSTANT == SQLITE_DETERMINISTIC from the API
** SQLITE_FUNC_DIRECT == SQLITE_DIRECTONLY from the API
** SQLITE_FUNC_UNSAFE == SQLITE_INNOCUOUS
** SQLITE_FUNC_MINMAX == NC_MinMaxAgg == SF_MinMaxAgg
** SQLITE_FUNC_ANYORDER == NC_OrderAgg == SF_OrderByReqd
** SQLITE_FUNC_LENGTH == OPFLAG_LENGTHARG
** SQLITE_FUNC_TYPEOF == OPFLAG_TYPEOFARG
** SQLITE_FUNC_CONSTANT == SQLITE_DETERMINISTIC from the API
** SQLITE_FUNC_DIRECT == SQLITE_DIRECTONLY from the API
** SQLITE_FUNC_UNSAFE == SQLITE_INNOCUOUS
** SQLITE_FUNC_ENCMASK depends on SQLITE_UTF* macros in the API
*/
#define SQLITE_FUNC_ENCMASK 0x0003 /* SQLITE_UTF8, SQLITE_UTF16BE or UTF16LE */
@@ -1853,6 +1855,7 @@ struct FuncDestructor {
#define SQLITE_FUNC_SUBTYPE 0x00100000 /* Result likely to have sub-type */
#define SQLITE_FUNC_UNSAFE 0x00200000 /* Function has side effects */
#define SQLITE_FUNC_INLINE 0x00400000 /* Functions implemented in-line */
#define SQLITE_FUNC_ANYORDER 0x08000000 /* count/min/max aggregate */
/* Identifier numbers for each in-line function */
#define INLINEFUNC_coalesce 0
@@ -3088,31 +3091,33 @@ struct NameContext {
** Allowed values for the NameContext, ncFlags field.
**
** Value constraints (all checked via assert()):
** NC_HasAgg == SF_HasAgg == EP_Agg
** NC_MinMaxAgg == SF_MinMaxAgg == SQLITE_FUNC_MINMAX
** NC_HasAgg == SF_HasAgg == EP_Agg
** NC_MinMaxAgg == SF_MinMaxAgg == SQLITE_FUNC_MINMAX
** NC_OrderAgg == SF_OrderByReqd == SQLITE_FUNC_ANYORDER
** NC_HasWin == EP_Win
**
*/
#define NC_AllowAgg 0x00001 /* Aggregate functions are allowed here */
#define NC_PartIdx 0x00002 /* True if resolving a partial index WHERE */
#define NC_IsCheck 0x00004 /* True if resolving a CHECK constraint */
#define NC_GenCol 0x00008 /* True for a GENERATED ALWAYS AS clause */
#define NC_HasAgg 0x00010 /* One or more aggregate functions seen */
#define NC_IdxExpr 0x00020 /* True if resolving columns of CREATE INDEX */
#define NC_SelfRef 0x0002e /* Combo: PartIdx, isCheck, GenCol, and IdxExpr */
#define NC_VarSelect 0x00040 /* A correlated subquery has been seen */
#define NC_UEList 0x00080 /* True if uNC.pEList is used */
#define NC_UAggInfo 0x00100 /* True if uNC.pAggInfo is used */
#define NC_UUpsert 0x00200 /* True if uNC.pUpsert is used */
#define NC_UBaseReg 0x00400 /* True if uNC.iBaseReg is used */
#define NC_MinMaxAgg 0x01000 /* min/max aggregates seen. See note above */
#define NC_Complex 0x02000 /* True if a function or subquery seen */
#define NC_AllowWin 0x04000 /* Window functions are allowed here */
#define NC_HasWin 0x08000 /* One or more window functions seen */
#define NC_IsDDL 0x10000 /* Resolving names in a CREATE statement */
#define NC_InAggFunc 0x20000 /* True if analyzing arguments to an agg func */
#define NC_FromDDL 0x40000 /* SQL text comes from sqlite_schema */
#define NC_NoSelect 0x80000 /* Do not descend into sub-selects */
#define NC_AllowAgg 0x000001 /* Aggregate functions are allowed here */
#define NC_PartIdx 0x000002 /* True if resolving a partial index WHERE */
#define NC_IsCheck 0x000004 /* True if resolving a CHECK constraint */
#define NC_GenCol 0x000008 /* True for a GENERATED ALWAYS AS clause */
#define NC_HasAgg 0x000010 /* One or more aggregate functions seen */
#define NC_IdxExpr 0x000020 /* True if resolving columns of CREATE INDEX */
#define NC_SelfRef 0x00002e /* Combo: PartIdx, isCheck, GenCol, and IdxExpr */
#define NC_VarSelect 0x000040 /* A correlated subquery has been seen */
#define NC_UEList 0x000080 /* True if uNC.pEList is used */
#define NC_UAggInfo 0x000100 /* True if uNC.pAggInfo is used */
#define NC_UUpsert 0x000200 /* True if uNC.pUpsert is used */
#define NC_UBaseReg 0x000400 /* True if uNC.iBaseReg is used */
#define NC_MinMaxAgg 0x001000 /* min/max aggregates seen. See note above */
#define NC_Complex 0x002000 /* True if a function or subquery seen */
#define NC_AllowWin 0x004000 /* Window functions are allowed here */
#define NC_HasWin 0x008000 /* One or more window functions seen */
#define NC_IsDDL 0x010000 /* Resolving names in a CREATE statement */
#define NC_InAggFunc 0x020000 /* True if analyzing arguments to an agg func */
#define NC_FromDDL 0x040000 /* SQL text comes from sqlite_schema */
#define NC_NoSelect 0x080000 /* Do not descend into sub-selects */
#define NC_OrderAgg 0x8000000 /* Has an aggregate other than count/min/max */
/*
** An instance of the following object describes a single ON CONFLICT
@@ -3195,9 +3200,10 @@ struct Select {
** "Select Flag".
**
** Value constraints (all checked via assert())
** SF_HasAgg == NC_HasAgg
** SF_MinMaxAgg == NC_MinMaxAgg == SQLITE_FUNC_MINMAX
** SF_FixedLimit == WHERE_USE_LIMIT
** SF_HasAgg == NC_HasAgg
** SF_MinMaxAgg == NC_MinMaxAgg == SQLITE_FUNC_MINMAX
** SF_OrderByReqd == NC_OrderAgg == SQLITE_FUNC_ANYORDER
** SF_FixedLimit == WHERE_USE_LIMIT
*/
#define SF_Distinct 0x0000001 /* Output should be DISTINCT */
#define SF_All 0x0000002 /* Includes the ALL keyword */
@@ -3226,6 +3232,7 @@ struct Select {
#define SF_PushDown 0x1000000 /* SELECT has be modified by push-down opt */
#define SF_MultiPart 0x2000000 /* Has multiple incompatible PARTITIONs */
#define SF_CopyCte 0x4000000 /* SELECT statement is a copy of a CTE */
#define SF_OrderByReqd 0x8000000 /* The ORDER BY clause may not be purged */
/*
** The results of a SELECT can be distributed in several ways, as defined