Revise the implementation of OP_Once so that it is smaller, faster, and uses

less memory.  This also fixes an obscure bug introduced 3 days ago by check-in
[5990a1bdb4a073].

FossilOrigin-Name: 6bf5ba10d28f1b0a32aa9a560ae3143a1235eadb

manifest

@@ -1,5 +1,5 @@
-C Minor\senhancement\sto\sthe\sTclKit\sbatch\stool:\sit\sshould\sdownload\sthe\sTclKit\sEXE\salone\swhen\sthe\sTCLKIT_NOENV\senvironment\svariable\sis\sset.
+C Revise\sthe\simplementation\sof\sOP_Once\sso\sthat\sit\sis\ssmaller,\sfaster,\sand\suses\nless\smemory.\s\sThis\salso\sfixes\san\sobscure\sbug\sintroduced\s3\sdays\sago\sby\scheck-in\n[5990a1bdb4a073].
-D 2016-09-17T22:46:13.833
+D 2016-09-18T16:08:10.162
 F Makefile.in 6fd48ffcf7c2deea7499062d1f3747f986c19678
 F Makefile.linux-gcc 7bc79876b875010e8c8f9502eb935ca92aa3c434
 F Makefile.msc e1aa788e84f926e42239ee167c53f785bedacacd
@@ -339,11 +339,11 @@ F src/ctime.c e77f3dc297b4b65c96da78b4ae4272fdfae863d7
 F src/date.c 95c9a8d00767e7221a8e9a31f4e913fc8029bf6b
 F src/dbstat.c 19ee7a4e89979d4df8e44cfac7a8f905ec89b77d
 F src/delete.c e91a11e0e86a13ce1917ca5ad7cf14c37ba31e59
-F src/expr.c c1de78269522de39f6ad877ab0810a5d48f91f34
+F src/expr.c 5f6c8263b021853aef5a43e920efebd0b94de394
 F src/fault.c 160a0c015b6c2629d3899ed2daf63d75754a32bb
 F src/fkey.c e2be0968c1adc679c87e467aa5b4f167588f38a8
 F src/func.c 29cc9acb170ec1387b9f63eb52cd85f8de96c771
-F src/global.c c45ea22aff29334f6a9ec549235ac3357c970015
+F src/global.c 2917bbc488201b791e5f5dd43d8d2a3ccc315da7
 F src/hash.c 55b5fb474100cee0b901edaf203e26c970940f36
 F src/hash.h ab34c5c54a9e9de2e790b24349ba5aab3dbb4fd4
 F src/hwtime.h 747c1bbe9df21a92e9c50f3bbec1de841dc5e5da
@@ -351,7 +351,7 @@ F src/in-operator.md 10cd8f4bcd225a32518407c2fb2484089112fd71
 F src/insert.c 427e96ff168b6b187a52c3d06b9f9e41f6ffb212
 F src/legacy.c 75d3023be8f0d2b99d60f905090341a03358c58e
 F src/loadext.c 5d6642d141c07d366e43d359e94ec9de47add41d
-F src/main.c 9821bb4d2399bc5a0b8a5dfc06bede2d1520255c
+F src/main.c 14fb66eeb2eea477f9e79434fde3cca3aff0ea5c
 F src/malloc.c 1443d1ad95d67c21d77af7ae3f44678252f0efec
 F src/mem0.c 6a55ebe57c46ca1a7d98da93aaa07f99f1059645
 F src/mem1.c 6919bcf12f221868ea066eec27e579fed95ce98b
@@ -388,10 +388,10 @@ F src/resolve.c 3c3cf0dc719cd2a32ab5c1e10c26481dd565492e
 F src/rowset.c 7b7e7e479212e65b723bf40128c7b36dc5afdfac
 F src/select.c 244f9cc5e4662987cd2ef5c22d1b7027560f3425
 F src/shell.c b80396d2fadce4681397707e30078bf416e1dec2
-F src/sqlite.h.in 46ed821aeed0ba45559fb15597d9a400083154a2
+F src/sqlite.h.in 2683a291ed8db5228024267be6421f0de507b80e
 F src/sqlite3.rc 5121c9e10c3964d5755191c80dd1180c122fc3a8
 F src/sqlite3ext.h 8648034aa702469afb553231677306cc6492a1ae
-F src/sqliteInt.h c9e010a79ab4ed7bdc910a24d8f08f3c6d5f822c
+F src/sqliteInt.h 1abb4501bbc28c9badf0ebc1e99bd66585ba04f0
 F src/sqliteLimit.h c0373387c287c8d0932510b5547ecde31b5da247
 F src/status.c a9e66593dfb28a9e746cba7153f84d49c1ddc4b1
 F src/table.c 5226df15ab9179b9ed558d89575ea0ce37b03fc9
@@ -448,16 +448,16 @@ F src/test_wsd.c 41cadfd9d97fe8e3e4e44f61a4a8ccd6f7ca8fe9
 F src/threads.c 4ae07fa022a3dc7c5beb373cf744a85d3c5c6c3c
 F src/tokenize.c 78c8085bc7af1922aa687f0f4bbd716821330de5
 F src/treeview.c f51b75a28b377adde9f79bc3deb6c7770bcf97c0
-F src/trigger.c cae81f6c65c4977bc2cbd27d43bfee478710853c
+F src/trigger.c 3419bb9862983d84d70735fb4c94b21b934cd0c5
 F src/update.c 8179e699dbd45b92934fd02d3d8e3732e8da8802
 F src/utf.c 699001c79f28e48e9bcdf8a463da029ea660540c
 F src/util.c 810ec3f22e2d1b62e66c30fe3621ebdedd23584d
 F src/vacuum.c 913970b9d86dd6c2b8063ef1af421880f1464ec3
-F src/vdbe.c bd7e890b2d6e2c93c808e5cf0f8e9fb26198d0fc
+F src/vdbe.c cdac9f8c53e2992816809a45910ff33b6122c191
-F src/vdbe.h 67bc551f7faf04c33493892e4b378aada823ed10
+F src/vdbe.h c044be7050ac6bf596eecc6ab159f5dbc020a3b7
-F src/vdbeInt.h c59381049af5c7751a83456c39b80d1a6fde1f9d
+F src/vdbeInt.h d21f14721dd87975dc9e3bcdbf504f9c098cf611
 F src/vdbeapi.c a32d61b7dd05e6890d8fd44d2805f55e2f5ba9f3
-F src/vdbeaux.c 12831f89de66a23d575d129dc1bda543a09a80c7
+F src/vdbeaux.c 66054df369ca76530b6b84e6fce2f847dc99a9b1
 F src/vdbeblob.c 3e82a797b60c3b9fed7b8de8c539ca7607874937
 F src/vdbemem.c 357caac1a404f37ee6087b17613f92107c13f733
 F src/vdbesort.c 91fda3909326860382b0ca8aa251e609c6a9d62c
@@ -1525,7 +1525,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 63962e2a927963575be74c3ce11f39f722c07c72
+P baceb988c6f4e93134e6a63173e846af2b73531a
-R a636a72a27c00683275c0e840ed0e183
+R 305c67fde695fcddb65717c9957658ad
-U mistachkin
+U drh
-Z c511a2952b921071fe5b6c44565784ab
+Z 45869286482c6f2c4387b12de5cab0cb

manifest.uuid

@@ -1 +1 @@
-baceb988c6f4e93134e6a63173e846af2b73531a
+6bf5ba10d28f1b0a32aa9a560ae3143a1235eadb

src/expr.c

@@ -1974,7 +1974,7 @@ static Select *isCandidateForInOpt(Expr *pX){
 */
 int sqlite3CodeOnce(Parse *pParse){
   Vdbe *v = sqlite3GetVdbe(pParse);      /* Virtual machine being coded */
-  return sqlite3VdbeAddOp1(v, OP_Once, pParse->nOnce++);
+  return sqlite3VdbeAddOp0(v, OP_Once);
 }
 
 #ifndef SQLITE_OMIT_SUBQUERY

src/global.c

@@ -225,7 +225,8 @@ SQLITE_WSD struct Sqlite3Config sqlite3Config = {
 #ifndef SQLITE_OMIT_BUILTIN_TEST
    0,                         /* xTestCallback */
 #endif
-   0                          /* bLocaltimeFault */
+   0,                         /* bLocaltimeFault */
+   0x7ffffffe                 /* iOnceResetThreshold */
 };
 
 /*

src/main.c

@@ -3784,6 +3784,15 @@ int sqlite3_test_control(int op, ...){
       break;
     }
 
+    /* Set the threshold at which OP_Once counters reset back to zero.
+    ** By default this is 0xfffffffe (over 2 billion), but that value is
+    ** too big to test in a reasonable amount of time, so this control is
+    ** provided to set a small and easily reachable reset value.
+    */
+    case SQLITE_TESTCTRL_ONCE_RESET_THRESHOLD: {
+      sqlite3GlobalConfig.iOnceResetThreshold = va_arg(ap, int);
+      break;
+    }
 
     /*   sqlite3_test_control(SQLITE_TESTCTRL_VDBE_COVERAGE, xCallback, ptr);
     **

src/sqlite.h.in

@@ -6717,6 +6717,7 @@ int sqlite3_test_control(int op, ...);
 #define SQLITE_TESTCTRL_SCRATCHMALLOC           17
 #define SQLITE_TESTCTRL_LOCALTIME_FAULT         18
 #define SQLITE_TESTCTRL_EXPLAIN_STMT            19  /* NOT USED */
+#define SQLITE_TESTCTRL_ONCE_RESET_THRESHOLD    19
 #define SQLITE_TESTCTRL_NEVER_CORRUPT           20
 #define SQLITE_TESTCTRL_VDBE_COVERAGE           21
 #define SQLITE_TESTCTRL_BYTEORDER               22

src/sqliteInt.h

@@ -2896,7 +2896,6 @@ struct Parse {
   int nTab;            /* Number of previously allocated VDBE cursors */
   int nMem;            /* Number of memory cells used so far */
   int nSet;            /* Number of sets used so far */
-  int nOnce;           /* Number of OP_Once instructions so far */
   int nOpAlloc;        /* Number of slots allocated for Vdbe.aOp[] */
   int szOpAlloc;       /* Bytes of memory space allocated for Vdbe.aOp[] */
   int iFixedOp;        /* Never back out opcodes iFixedOp-1 or earlier */
@@ -3230,6 +3229,7 @@ struct Sqlite3Config {
   int (*xTestCallback)(int);        /* Invoked by sqlite3FaultSim() */
 #endif
   int bLocaltimeFault;              /* True to fail localtime() calls */
+  int iOnceResetThreshold;          /* When to reset OP_Once counters */
 };
 
 /*

src/trigger.c

@@ -879,7 +879,6 @@ static TriggerPrg *codeRowTrigger(
     }
     pProgram->nMem = pSubParse->nMem;
     pProgram->nCsr = pSubParse->nTab;
-    pProgram->nOnce = pSubParse->nOnce;
     pProgram->token = (void *)pTrigger;
     pPrg->aColmask[0] = pSubParse->oldmask;
     pPrg->aColmask[1] = pSubParse->newmask;

src/vdbe.c

@@ -2332,22 +2332,18 @@ case OP_BitNot: {             /* same as TK_BITNOT, in1, out2 */
 
 /* Opcode: Once P1 P2 * * *
 **
-** Check the "once" flag number P1. If it is set, jump to instruction P2. 
+** If the P1 value is equal to the P1 value on the OP_Init opcode at
-** Otherwise, set the flag and fall through to the next instruction.
+** instruction 0, then jump to P2.  If the two P1 values differ, then
-** In other words, this opcode causes all following opcodes up through P2
+** set the P1 value on this opcode to equal the P1 value on the OP_Init
-** (but not including P2) to run just once and to be skipped on subsequent
+** and fall through.
-** times through the loop.
-**
-** All "once" flags are initially cleared whenever a prepared statement
-** first begins to run.
 */
 case OP_Once: {             /* jump */
-  assert( pOp->p1<p->nOnceFlag );
+  assert( p->aOp[0].opcode==OP_Init );
-  VdbeBranchTaken(p->aOnceFlag[pOp->p1]!=0, 2);
+  VdbeBranchTaken(p->aOp[0].p1==pOp->p1, 2);
-  if( p->aOnceFlag[pOp->p1] ){
+  if( p->aOp[0].p1==pOp->p1 ){
     goto jump_to_p2;
   }else{
-    p->aOnceFlag[pOp->p1] = 1;
+    pOp->p1 = p->aOp[0].p1;
   }
   break;
 }
@@ -5790,8 +5786,7 @@ case OP_Program: {        /* jump */
     if( pProgram->nCsr==0 ) nMem++;
     nByte = ROUND8(sizeof(VdbeFrame))
               + nMem * sizeof(Mem)
-              + pProgram->nCsr * sizeof(VdbeCursor *)
+              + pProgram->nCsr * sizeof(VdbeCursor *);
-              + pProgram->nOnce * sizeof(u8);
     pFrame = sqlite3DbMallocZero(db, nByte);
     if( !pFrame ){
       goto no_mem;
@@ -5811,8 +5806,6 @@ case OP_Program: {        /* jump */
     pFrame->aOp = p->aOp;
     pFrame->nOp = p->nOp;
     pFrame->token = pProgram->token;
-    pFrame->aOnceFlag = p->aOnceFlag;
-    pFrame->nOnceFlag = p->nOnceFlag;
 #ifdef SQLITE_ENABLE_STMT_SCANSTATUS
     pFrame->anExec = p->anExec;
 #endif
@@ -5846,13 +5839,10 @@ case OP_Program: {        /* jump */
   p->apCsr = (VdbeCursor **)&aMem[p->nMem];
   p->aOp = aOp = pProgram->aOp;
   p->nOp = pProgram->nOp;
-  p->aOnceFlag = (u8 *)&p->apCsr[p->nCursor];
-  p->nOnceFlag = pProgram->nOnce;
 #ifdef SQLITE_ENABLE_STMT_SCANSTATUS
   p->anExec = 0;
 #endif
   pOp = &aOp[-1];
-  memset(p->aOnceFlag, 0, p->nOnceFlag);
 
   break;
 }
@@ -6819,7 +6809,7 @@ case OP_MaxPgcnt: {            /* out2 */
 #endif
 
 
-/* Opcode: Init * P2 * P4 *
+/* Opcode: Init P1 P2 * P4 *
 ** Synopsis: Start at P2
 **
 ** Programs contain a single instance of this opcode as the very first
@@ -6830,9 +6820,13 @@ case OP_MaxPgcnt: {            /* out2 */
 ** Or if P4 is blank, use the string returned by sqlite3_sql().
 **
 ** If P2 is not zero, jump to instruction P2.
+**
+** Increment the value of P1 so that OP_Once opcodes will jump the
+** first time they are evaluated for this run.
 */
 case OP_Init: {          /* jump */
   char *zTrace;
+  int i;
 
   /* If the P4 argument is not NULL, then it must be an SQL comment string.
   ** The "--" string is broken up to prevent false-positives with srcck1.c.
@@ -6844,6 +6838,7 @@ case OP_Init: {          /* jump */
   ** sqlite3_expanded_sql(P) otherwise.
   */
   assert( pOp->p4.z==0 || strncmp(pOp->p4.z, "-" "- ", 3)==0 );
+  assert( pOp==p->aOp );  /* Always instruction 0 */
 
 #ifndef SQLITE_OMIT_TRACE
   if( (db->mTrace & (SQLITE_TRACE_STMT|SQLITE_TRACE_LEGACY))!=0
@@ -6881,6 +6876,13 @@ case OP_Init: {          /* jump */
 #endif /* SQLITE_DEBUG */
 #endif /* SQLITE_OMIT_TRACE */
   assert( pOp->p2>0 );
+  if( pOp->p1>=sqlite3GlobalConfig.iOnceResetThreshold ){
+    for(i=1; i<p->nOp; i++){
+      if( p->aOp[i].opcode==OP_Once ) p->aOp[i].p1 = 0;
+    }
+    pOp->p1 = 0;
+  }
+  pOp->p1++;
   goto jump_to_p2;
 }
 

src/vdbe.h

@@ -88,7 +88,6 @@ struct SubProgram {
   int nOp;                      /* Elements in aOp[] */
   int nMem;                     /* Number of memory cells required */
   int nCsr;                     /* Number of cursors required */
-  int nOnce;                    /* Number of OP_Once instructions */
   void *token;                  /* id that may be used to recursive triggers */
   SubProgram *pNext;            /* Next sub-program already visited */
 };

src/vdbeInt.h

@@ -157,7 +157,6 @@ struct VdbeFrame {
   Op *aOp;                /* Program instructions for parent frame */
   i64 *anExec;            /* Event counters from parent frame */
   Mem *aMem;              /* Array of memory cells for parent frame */
-  u8 *aOnceFlag;          /* Array of OP_Once flags for parent frame */
   VdbeCursor **apCsr;     /* Array of Vdbe cursors for parent frame */
   void *token;            /* Copy of SubProgram.token */
   i64 lastRowid;          /* Last insert rowid (sqlite3.lastRowid) */
@@ -166,7 +165,6 @@ struct VdbeFrame {
   int pc;                 /* Program Counter in parent (calling) frame */
   int nOp;                /* Size of aOp array */
   int nMem;               /* Number of entries in aMem */
-  int nOnceFlag;          /* Number of entries in aOnceFlag */
   int nChildMem;          /* Number of memory cells for child frame */
   int nChildCsr;          /* Number of cursors for child frame */
   int nChange;            /* Statement changes (Vdbe.nChange)     */
@@ -410,8 +408,6 @@ struct Vdbe {
   int nFrame;             /* Number of frames in pFrame list */
   u32 expmask;            /* Binding to these vars invalidates VM */
   SubProgram *pProgram;   /* Linked list of all sub-programs used by VM */
-  int nOnceFlag;          /* Size of array aOnceFlag[] */
-  u8 *aOnceFlag;          /* Flags for OP_Once */
   AuxData *pAuxData;      /* Linked list of auxdata allocations */
 #ifdef SQLITE_ENABLE_STMT_SCANSTATUS
   i64 *anExec;            /* Number of times each op has been executed */

src/vdbeaux.c

@@ -1869,7 +1869,6 @@ void sqlite3VdbeMakeReady(
   int nMem;                      /* Number of VM memory registers */
   int nCursor;                   /* Number of cursors required */
   int nArg;                      /* Number of arguments in subprograms */
-  int nOnce;                     /* Number of OP_Once instructions */
   int n;                         /* Loop counter */
   struct ReusableSpace x;        /* Reusable bulk memory */
 
@@ -1884,8 +1883,6 @@ void sqlite3VdbeMakeReady(
   nMem = pParse->nMem;
   nCursor = pParse->nTab;
   nArg = pParse->nMaxArg;
-  nOnce = pParse->nOnce;
-  if( nOnce==0 ) nOnce = 1; /* Ensure at least one byte in p->aOnceFlag[] */
   
   /* Each cursor uses a memory cell.  The first cursor (cursor 0) can
   ** use aMem[0] which is not otherwise used by the VDBE program.  Allocate
@@ -1932,7 +1929,6 @@ void sqlite3VdbeMakeReady(
     p->aVar = allocSpace(&x, p->aVar, nVar*sizeof(Mem));
     p->apArg = allocSpace(&x, p->apArg, nArg*sizeof(Mem*));
     p->apCsr = allocSpace(&x, p->apCsr, nCursor*sizeof(VdbeCursor*));
-    p->aOnceFlag = allocSpace(&x, p->aOnceFlag, nOnce);
 #ifdef SQLITE_ENABLE_STMT_SCANSTATUS
     p->anExec = allocSpace(&x, p->anExec, p->nOp*sizeof(i64));
 #endif
@@ -1942,7 +1938,6 @@ void sqlite3VdbeMakeReady(
   }while( !db->mallocFailed );
 
   p->nCursor = nCursor;
-  p->nOnceFlag = nOnce;
   if( p->aVar ){
     p->nVar = (ynVar)nVar;
     for(n=0; n<nVar; n++){
@@ -2030,8 +2025,6 @@ int sqlite3VdbeFrameRestore(VdbeFrame *pFrame){
 #ifdef SQLITE_ENABLE_STMT_SCANSTATUS
   v->anExec = pFrame->anExec;
 #endif
-  v->aOnceFlag = pFrame->aOnceFlag;
-  v->nOnceFlag = pFrame->nOnceFlag;
   v->aOp = pFrame->aOp;
   v->nOp = pFrame->nOp;
   v->aMem = pFrame->aMem;
@@ -2569,11 +2562,8 @@ int sqlite3VdbeHalt(Vdbe *p){
   ** one, or the complete transaction if there is no statement transaction.
   */
 
-  assert( p->aOnceFlag!=0 || db->mallocFailed );
   if( db->mallocFailed ){
     p->rc = SQLITE_NOMEM_BKPT;
-  }else{
-    memset(p->aOnceFlag, 0, p->nOnceFlag);
   }
   closeAllCursors(p);
   if( p->magic!=VDBE_MAGIC_RUN ){