[tarantool-patches] Re: [PATCH 1/4] sql: remove unused opcodes from OP_[Sorter/Idx][Insert/Replace]

[Vladislav Shpilevoy <v.shpilevoy@tarantool.org>]

Hello. See the diff at the end of the letter, and my responses to some of
your comments.
>> done in a primary index only. It is enough to pass a register of
>> a primary index.
> Nitpicking: not 'a register of a primary index’,
> but number of cursor opened on this space/index.
Here you are wrong - it is a register, where tuple data is stored to 
insert. Cursor id
argument is not changed. I fixed it in a new commit.
>
>> +		bool no_foreign_keys =
>> +			sqlite3FkReferences(pTab) == NULL ||
>> +			(user_session->sql_flags & SQLITE_ForeignKeys) == 0;
> AFAIK SQLITE_ForeignKeys flag is always set to be true
> (since we always use FK). Thus, you can remove this condition check.
Yes, Foreign Keys source code now is always built, because we have 
removed OMIT_FOREIGN_KEYS,
but SQLITE_ForeignKeys is not a #define - it is a flag, that can be set 
by a user on runtime in its
session, and allows to skip foreign keys checking. The removal of this 
flags must be discussed,
because I think it can be useful.

In any case, talking about the patch, I found a way to remove this code 
completely. See diff below.


diff --git a/src/box/sql/analyze.c b/src/box/sql/analyze.c
index c5dcedd3e..4eae896ab 100644
--- a/src/box/sql/analyze.c
+++ b/src/box/sql/analyze.c
@@ -1050,7 +1050,6 @@ analyzeOneTable(Parse * pParse,	/* Parser context */
  		sqlite3VdbeAddOp4(v, OP_MakeRecord, regTabname, 3, regTemp,
  				  "BBB", 0);
  		sqlite3VdbeAddOp2(v, OP_IdxInsert, iStatCur, regTemp);
-		sqlite3VdbeChangeP5(v, OPFLAG_APPEND);
  
  		/* Add the entries to the stat4 table. */
  
diff --git a/src/box/sql/build.c b/src/box/sql/build.c
index 5e3ed0f39..5c3cac881 100644
--- a/src/box/sql/build.c
+++ b/src/box/sql/build.c
@@ -2659,7 +2659,6 @@ sqlite3RefillIndex(Parse * pParse, Index * pIndex, int memRootPage)
  	sqlite3VdbeAddOp3(v, OP_SorterData, iSorter, regRecord, iIdx);
  	sqlite3VdbeAddOp3(v, OP_Last, iIdx, 0, -1);
  	sqlite3VdbeAddOp2(v, OP_IdxInsert, iIdx, regRecord);
-	sqlite3VdbeChangeP5(v, OPFLAG_USESEEKRESULT);
  	sqlite3ReleaseTempReg(pParse, regRecord);
  	sqlite3VdbeAddOp2(v, OP_SorterNext, iSorter, addr2);
  	VdbeCoverage(v);
diff --git a/src/box/sql/insert.c b/src/box/sql/insert.c
index c7fe92cd6..c76910e5b 100644
--- a/src/box/sql/insert.c
+++ b/src/box/sql/insert.c
@@ -851,23 +851,7 @@ sqlite3Insert(Parse * pParse,	/* Parser context */
  						ipkColumn >= 0, onError,
  						endOfLoop, &isReplace, 0);
  		sqlite3FkCheck(pParse, pTab, 0, regIns, 0);
-
-		/* Set the OPFLAG_USESEEKRESULT flag if either (a) there are no REPLACE
-		 * constraints or (b) there are no triggers and this table is not a
-		 * parent table in a foreign key constraint. It is safe to set the
-		 * flag in the second case as if any REPLACE constraint is hit, an
-		 * OP_Delete or OP_IdxDelete instruction will be executed on each
-		 * cursor that is disturbed. And these instructions both clear the
-		 * VdbeCursor.seekResult variable, disabling the OPFLAG_USESEEKRESULT
-		 * functionality.
-		 */
-		bool no_foreign_keys =
-			sqlite3FkReferences(pTab) == NULL ||
-			(user_session->sql_flags & SQLITE_ForeignKeys) == 0;
-		bool use_seek = isReplace == 0 ||
-				(pTrigger == NULL && no_foreign_keys);
-		vdbe_emit_complete_insertion(v, iIdxCur, aRegIdx[0], use_seek,
-					     onError);
+		vdbe_emit_insertion_completion(v, iIdxCur, aRegIdx[0], onError);
  	}
  
  	/* Update the count of rows that are inserted
@@ -1491,20 +1475,16 @@ sqlite3GenerateConstraintChecks(Parse * pParse,		/* The parser context */
  }
  
  void
-vdbe_emit_complete_insertion(Vdbe *v, int cursor_id, int tuple_id,
-			     bool use_seek_result, u8 on_error)
+vdbe_emit_insertion_completion(Vdbe *v, int cursor_id, int tuple_id, u8 on_error)
  {
  	assert(v != NULL);
-	u16 pik_flags = OPFLAG_NCHANGE;
-	if (use_seek_result)
-		pik_flags |= OPFLAG_USESEEKRESULT;
-
  	int opcode;
  	if (on_error == ON_CONFLICT_ACTION_REPLACE)
  		opcode = OP_IdxReplace;
  	else
  		opcode = OP_IdxInsert;
  
+	u16 pik_flags = OPFLAG_NCHANGE;
  	if (on_error == ON_CONFLICT_ACTION_IGNORE)
  		pik_flags |= OPFLAG_OE_IGNORE;
  	else if (on_error == ON_CONFLICT_ACTION_FAIL)
@@ -1910,7 +1890,6 @@ xferOptimization(Parse * pParse,	/* Parser context */
  	}
  
  	for (pDestIdx = pDest->pIndex; pDestIdx; pDestIdx = pDestIdx->pNext) {
-		u8 idxInsFlags = 0;
  		for (pSrcIdx = pSrc->pIndex; ALWAYS(pSrcIdx);
  		     pSrcIdx = pSrcIdx->pNext) {
  			if (xferCompatibleIndex(pDestIdx, pSrcIdx))
@@ -1927,11 +1906,9 @@ xferOptimization(Parse * pParse,	/* Parser context */
  		addr1 = sqlite3VdbeAddOp2(v, OP_Rewind, iSrc, 0);
  		VdbeCoverage(v);
  		sqlite3VdbeAddOp2(v, OP_RowData, iSrc, regData);
-		if (pDestIdx->idxType == SQLITE_IDXTYPE_PRIMARYKEY) {
-			idxInsFlags |= OPFLAG_NCHANGE;
-		}
  		sqlite3VdbeAddOp2(v, OP_IdxInsert, iDest, regData);
-		sqlite3VdbeChangeP5(v, idxInsFlags | OPFLAG_APPEND);
+		if (pDestIdx->idxType == SQLITE_IDXTYPE_PRIMARYKEY)
+			sqlite3VdbeChangeP5(v, OPFLAG_NCHANGE);
  		sqlite3VdbeAddOp2(v, OP_Next, iSrc, addr1 + 1);
  		VdbeCoverage(v);
  		sqlite3VdbeJumpHere(v, addr1);
diff --git a/src/box/sql/select.c b/src/box/sql/select.c
index 95bd7d656..9e64b434e 100644
--- a/src/box/sql/select.c
+++ b/src/box/sql/select.c
@@ -1151,7 +1151,6 @@ selectInnerLoop(Parse * pParse,		/* The parser context */
  			if (eDest == SRT_DistQueue) {
  				sqlite3VdbeAddOp2(v, OP_IdxInsert, iParm + 1,
  						  r3);
-				sqlite3VdbeChangeP5(v, OPFLAG_USESEEKRESULT);
  			}
  			for (i = 0; i < nKey; i++) {
  				sqlite3VdbeAddOp2(v, OP_SCopy,
diff --git a/src/box/sql/sqliteInt.h b/src/box/sql/sqliteInt.h
index e786cf842..7c0a214b5 100644
--- a/src/box/sql/sqliteInt.h
+++ b/src/box/sql/sqliteInt.h
@@ -3039,8 +3039,6 @@ struct Parse {
  				     /* Also used in P2 (not P5) of OP_Delete */
  #define OPFLAG_EPHEM         0x01	/* OP_Column: Ephemeral output is ok */
  #define OPFLAG_ISUPDATE      0x04	/* This OP_Insert is an sql UPDATE */
-#define OPFLAG_APPEND        0x08	/* This is likely to be an append */
-#define OPFLAG_USESEEKRESULT 0x10	/* Try to avoid a seek in BtreeInsert() */
  #define OPFLAG_OE_IGNORE    0x200	/* OP_IdxInsert: Ignore flag */
  #define OPFLAG_OE_FAIL      0x400	/* OP_IdxInsert: Fail flag */
  #ifdef SQLITE_ENABLE_PREUPDATE_HOOK
@@ -3722,13 +3720,11 @@ void sqlite3GenerateConstraintChecks(Parse *, Table *, int *, int, int, int,
   * @param v Virtual database engine.
   * @param cursor_id Primary index cursor.
   * @param tuple_id Register with data to insert.
- * @param use_seek_result True to set the USESEEKRESULT flag on
- *        OP_[Idx]Insert.
   * @param on_error Error action on failed insert/replace.
   */
  void
-vdbe_emit_complete_insertion(Vdbe *v, int cursor_id, int tuple_id,
-			     bool use_seek_result, u8 on_error);
+vdbe_emit_insertion_completion(Vdbe *v, int cursor_id, int tuple_id,
+			       u8 on_error);
  
  int sqlite3OpenTableAndIndices(Parse *, Table *, int, u8, int, u8 *, int *,
  			       int *, u8, u8);
diff --git a/src/box/sql/update.c b/src/box/sql/update.c
index 859189a7e..98e696ddf 100644
--- a/src/box/sql/update.c
+++ b/src/box/sql/update.c
@@ -615,8 +615,7 @@ sqlite3Update(Parse * pParse,		/* The parser context */
  		}
  
  		/* Insert the new index entries and the new record. */
-		vdbe_emit_complete_insertion(v, iIdxCur, aRegIdx[0], false,
-					     onError);
+		vdbe_emit_insertion_completion(v, iIdxCur, aRegIdx[0], onError);
  
  		/* Do any ON CASCADE, SET NULL or SET DEFAULT operations required to
  		 * handle rows (possibly in other tables) that refer via a foreign key
diff --git a/src/box/sql/vdbe.c b/src/box/sql/vdbe.c
index bf8a27709..5a56727da 100644
--- a/src/box/sql/vdbe.c
+++ b/src/box/sql/vdbe.c
@@ -4321,24 +4321,11 @@ case OP_Next:          /* jump */
  /* Opcode: IdxInsert P1 P2 * * P5
   * Synopsis: key=r[P2]
   *
- * Register P2 holds an SQL index key made using the
- * MakeRecord instructions.  This opcode writes that key
- * into the index P1.  Data for the entry is nil.
- *
- * If P5 has the OPFLAG_APPEND bit set, that is a hint to the b-tree layer
- * that this insert is likely to be an append.
- *
- * If P5 has the OPFLAG_NCHANGE bit set, then the change counter is
- * incremented by this instruction.  If the OPFLAG_NCHANGE bit is clear,
- * then the change counter is unchanged.
- *
- * If the OPFLAG_USESEEKRESULT flag of P5 is set, the implementation might
- * run faster by avoiding an unnecessary seek on cursor P1.  However,
- * the OPFLAG_USESEEKRESULT flag must only be set if there have been no prior
- * seeks on the cursor or if the most recent seek used a key equivalent
- * to P2.
- *
- * This instruction only works for indices.
+ * @param P1 Index of a space cursor.
+ * @param P2 Index of a register with MessagePack data to insert.
+ * @param P5 Flags. If P5 contains OPFLAG_NCHANGE, then VDBE
+ *        accounts the change in a case of successful insertion in
+ *        nChange counter.
   */
  /* Opcode: IdxReplace P1 P2 * * P5
   * Synopsis: key=r[P2]
diff --git a/src/box/sql/where.c b/src/box/sql/where.c
index 79de5d69a..c51bd7455 100644
--- a/src/box/sql/where.c
+++ b/src/box/sql/where.c
@@ -844,7 +844,6 @@ constructAutomaticIndex(Parse * pParse,			/* The parsing context */
  	    sqlite3GenerateIndexKey(pParse, pIdx, pLevel->iTabCur, regRecord, 0,
  				    0, 0);
  	sqlite3VdbeAddOp2(v, OP_IdxInsert, pLevel->iIdxCur, regRecord);
-	sqlite3VdbeChangeP5(v, OPFLAG_USESEEKRESULT);
  	if (pPartial)
  		sqlite3VdbeResolveLabel(v, iContinue);
  	if (pTabItem->fg.viaCoroutine) {
diff --git a/src/box/sql/wherecode.c b/src/box/sql/wherecode.c
index a3c51eef4..aaffa7c1c 100644
--- a/src/box/sql/wherecode.c
+++ b/src/box/sql/wherecode.c
@@ -1766,10 +1766,6 @@ sqlite3WhereCodeOneLoopStart(WhereInfo * pWInfo,	/* Complete information about t
  							sqlite3VdbeAddOp2
  								(v, OP_IdxInsert,
  								 regRowset, regPk);
-							if (iSet)
-								sqlite3VdbeChangeP5
-									(v,
-									 OPFLAG_USESEEKRESULT);
  						}
  
  						/* Release the array of temp registers */