Remove rows from the ephemeral table used by window functions once they are no longer required.

FossilOrigin-Name: 6ad553192051eaa0c6d929baacde2de07b93c6d09de861028bbce55a2c9bfdd3

manifest

@@ -1,5 +1,5 @@
-C Minor\soptimization\sin\ssqlite3WindowCodeStep().
-D 2019-03-13T08:28:51.566
+C Remove\srows\sfrom\sthe\sephemeral\stable\sused\sby\swindow\sfunctions\sonce\sthey\sare\sno\slonger\srequired.
+D 2019-03-13T15:29:14.931
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F Makefile.in 236d2739dc3e823c3c909bca2d6cef93009bafbefd7018a8f3281074ecb92954
@@ -456,7 +456,7 @@ F src/auth.c 0fac71038875693a937e506bceb492c5f136dd7b1249fbd4ae70b4e8da14f9df
 F src/backup.c 78d3cecfbe28230a3a9a1793e2ead609f469be43e8f486ca996006be551857ab
 F src/bitvec.c 17ea48eff8ba979f1f5b04cc484c7bb2be632f33
 F src/btmutex.c 8acc2f464ee76324bf13310df5692a262b801808984c1b79defb2503bbafadb6
-F src/btree.c 51ff9c432f55f7fb8dca32d96707bc191327c1e29b1b83769d3ff6486df3948b
+F src/btree.c 3aa86a5230912958908564b465b0893e5fa98aac61cd255591f8fe58c85390a6
 F src/btree.h 63b94fb38ce571c15eb6a3661815561b501d23d5948b2d1e951fbd7a2d04e8d3
 F src/btreeInt.h 6111c15868b90669f79081039d19e7ea8674013f907710baa3c814dc3f8bfd3f
 F src/build.c 3acec29b23948042173301a8befebae01a98344debf66cbd4467c8b9077707b8
@@ -604,7 +604,7 @@ F src/where.c 8a207cb2ca6b99e1edb1e4bbff9b0504385a759cbf66180d1deb34d80ca4b799
 F src/whereInt.h 5f14db426ca46a83eabab1ae9aa6d4b8f27504ad35b64c290916289b1ddb2e88
 F src/wherecode.c ce7b21e1be2b981d62683fc59c4ca73a04a7ff2f1ebec23d41baf2da2349afd6
 F src/whereexpr.c 36b47f7261d6b6f1a72d774c113b74beddf6745aba1018e64b196e29db233442
-F src/window.c ac687a055121a757d951584285d1ae4554245f98cd17f6092118b29c17340d8f
+F src/window.c e05db1c6684a5ee877c930edbb7186e887bbcd756124db6dc4bf423f6f5a10fd
 F test/8_3_names.test ebbb5cd36741350040fd28b432ceadf495be25b2
 F test/affinity2.test a6d901b436328bd67a79b41bb0ac2663918fe3bd
 F test/affinity3.test 6a101af2fc945ce2912f6fe54dd646018551710d
@@ -1812,7 +1812,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 25ff7091cb12c63b1864ce68a9151f8432af5804b5ae905a2175761ab4b9fdd8
-R 8c316b11f34d1b1237d8105ff52ba315
+P b1322ffb6e63a110998068bf4f0a903028bd4fc0464ae1e517d745fb46423f39
+R ab6734715fa673e5e023d8c418a37782
 U dan
-Z b674509c0d99256be9c341d8d5499a74
+Z ae82d7d89959a9f160b7f989622338e5

manifest.uuid

@@ -1 +1 @@
-b1322ffb6e63a110998068bf4f0a903028bd4fc0464ae1e517d745fb46423f39
+6ad553192051eaa0c6d929baacde2de07b93c6d09de861028bbce55a2c9bfdd3

src/btree.c

@@ -8828,9 +8828,13 @@ int sqlite3BtreeDelete(BtCursor *pCur, u8 flags){
   assert( pCur->curFlags & BTCF_WriteFlag );
   assert( hasSharedCacheTableLock(p, pCur->pgnoRoot, pCur->pKeyInfo!=0, 2) );
   assert( !hasReadConflicts(p, pCur->pgnoRoot) );
-  assert( pCur->ix<pCur->pPage->nCell );
-  assert( pCur->eState==CURSOR_VALID );
   assert( (flags & ~(BTREE_SAVEPOSITION | BTREE_AUXDELETE))==0 );
+  if( pCur->eState==CURSOR_REQUIRESEEK ){
+    rc = btreeRestoreCursorPosition(pCur);
+    if( rc ) return rc;
+  }
+  assert( pCur->eState==CURSOR_VALID );
+  assert( pCur->ix<pCur->pPage->nCell );
 
   iCellDepth = pCur->iPage;
   iCellIdx = pCur->ix;

src/window.c

@@ -611,6 +611,7 @@ void sqlite3WindowUpdate(
         { cume_distName,    TK_GROUPS, TK_FOLLOWING, TK_UNBOUNDED }, 
         { ntileName,        TK_ROWS,   TK_CURRENT,   TK_UNBOUNDED }, 
         { leadName,         TK_ROWS,   TK_UNBOUNDED, TK_UNBOUNDED }, 
+        { lagName,          TK_ROWS,   TK_UNBOUNDED, TK_CURRENT }, 
       };
       int i;
       for(i=0; i<ArraySize(aUp); i++){
@@ -1472,7 +1473,6 @@ static int windowInitAccum(Parse *pParse, Window *pMWin){
   return regArg;
 }
 
-#if 0
 /* 
 ** Return true if the current frame should be cached in the ephemeral table,
 ** even if there are no xInverse() calls required.
@@ -1483,7 +1483,7 @@ static int windowCacheFrame(Window *pMWin){
     FuncDef *pFunc = pWin->pFunc;
     if( (pFunc->zName==nth_valueName)
      || (pFunc->zName==first_valueName)
-     || (pFunc->zName==leadName) */
+     || (pFunc->zName==leadName)
      || (pFunc->zName==lagName)
     ){
       return 1;
@@ -1491,7 +1491,6 @@ static int windowCacheFrame(Window *pMWin){
   }
   return 0;
 }
-#endif
 
 /*
 ** regOld and regNew are each the first register in an array of size
@@ -1532,6 +1531,7 @@ struct WindowCsrAndReg {
   int csr;
   int reg;
 };
+
 struct WindowCodeArg {
   Parse *pParse;
   Window *pMWin;
@@ -1539,12 +1539,16 @@ struct WindowCodeArg {
   int regGosub;
   int addrGosub;
   int regArg;
+  int eDelete;
 
   WindowCsrAndReg start;
   WindowCsrAndReg current;
   WindowCsrAndReg end;
 };
 
+/*
+** Values that may be passed as the second argument to windowCodeOp().
+*/
 #define WINDOW_RETURN_ROW 1
 #define WINDOW_AGGINVERSE 2
 #define WINDOW_AGGSTEP    3
@@ -1701,6 +1705,11 @@ static int windowCodeOp(
       break;
   }
 
+  if( op==p->eDelete ){
+    sqlite3VdbeAddOp1(v, OP_Delete, csr);
+    sqlite3VdbeChangeP5(v, OPFLAG_SAVEPOSITION);
+  }
+
   if( jumpOnEof ){
     sqlite3VdbeAddOp2(v, OP_Next, csr, sqlite3VdbeCurrentAddr(v)+2);
     ret = sqlite3VdbeAddOp0(v, OP_Goto);
@@ -1712,7 +1721,6 @@ static int windowCodeOp(
   }
 
   if( bPeer ){
-    int addr;
     int nReg = (pMWin->pOrderBy ? pMWin->pOrderBy->nExpr : 0);
     int regTmp = (nReg ? sqlite3GetTempRange(pParse, nReg) : 0);
     windowReadPeerValues(p, csr, regTmp);
@@ -2154,6 +2162,37 @@ void sqlite3WindowCodeStep(
   s.start.csr = s.current.csr+2;
   s.end.csr = s.current.csr+3;
 
+  /* Figure out when rows may be deleted from the ephemeral table. There
+  ** are four options - they may never be deleted (eDelete==0), they may 
+  ** be deleted as soon as they are no longer part of the window frame
+  ** (eDelete==WINDOW_AGGINVERSE), they may be deleted as after the row 
+  ** has been returned to the caller (WINDOW_RETURN_ROW), or they may
+  ** be deleted after they enter the frame (WINDOW_AGGSTEP). */
+  switch( pMWin->eStart ){
+    case TK_FOLLOWING: {
+      sqlite3 *db = pParse->db;
+      sqlite3_value *pVal = 0;
+      sqlite3ValueFromExpr(db, pMWin->pStart, db->enc,SQLITE_AFF_NUMERIC,&pVal);
+      if( pVal && sqlite3_value_int(pVal)>0 ){
+        s.eDelete = WINDOW_RETURN_ROW;
+      }
+      sqlite3ValueFree(pVal);
+      break;
+    }
+    case TK_UNBOUNDED:
+      if( windowCacheFrame(pMWin)==0 ){
+        if( pMWin->eEnd==TK_PRECEDING ){
+          s.eDelete = WINDOW_AGGSTEP;
+        }else{
+          s.eDelete = WINDOW_RETURN_ROW;
+        }
+      }
+      break;
+    default:
+      s.eDelete = WINDOW_AGGINVERSE;
+      break;
+  }
+
   /* Allocate registers for the array of values from the sub-query, the
   ** samve values in record form, and the rowid used to insert said record
   ** into the ephemeral table.  */