Add support for the 'txn' argument to date/time functions that works like

'now' but keeps the same time for the entire transaction.

FossilOrigin-Name: 5e4f45af96247e29910403a63ac148cb313b005f9c014b37a9a49d98f5fef9a6

src/date.c

@@ -331,11 +331,13 @@ static int parseYyyyMmDd(const char *zDate, DateTime *p){
 }
 
 /*
-** Set the time to the current time reported by the VFS.
+** Set the time to the current time reported for the prepared statement
+** that is currently executing.  The same time is reported for all
+** invocations of this routine from within the same call to sqlite3_step().
 **
 ** Return the number of errors.
 */
-static int setDateTimeToCurrent(sqlite3_context *context, DateTime *p){
+static int setCurrentStmtTime(sqlite3_context *context, DateTime *p){
   p->iJD = sqlite3StmtCurrentTime(context);
   if( p->iJD>0 ){
     p->validJD = 1;
@@ -345,6 +347,23 @@ static int setDateTimeToCurrent(sqlite3_context *context, DateTime *p){
   }
 }
 
+/*
+** Set the time to the current time reported for the current transaction.
+** The same time is set for all calls to this routine within the same
+** transaction.
+**
+** Return the number of errors.
+*/
+static int setCurrentTxnTime(sqlite3_context *context, DateTime *p){
+  p->iJD = sqlite3TxnCurrentTime(context);
+  if( p->iJD>0 ){
+    p->validJD = 1;
+    return 0;
+  }else{
+    return 1;
+  }
+}
+
 /*
 ** Input "r" is a numeric quantity which might be a julian day number,
 ** or the number of seconds since 1970.  If the value if r is within
@@ -387,7 +406,9 @@ static int parseDateOrTime(
   }else if( parseHhMmSs(zDate, p)==0 ){
     return 0;
   }else if( sqlite3StrICmp(zDate,"now")==0 && sqlite3NotPureFunc(context) ){
-    return setDateTimeToCurrent(context, p);
+    return setCurrentStmtTime(context, p);
+  }else if( sqlite3StrICmp(zDate,"txn")==0 && sqlite3NotPureFunc(context) ){
+    return setCurrentTxnTime(context, p);
   }else if( sqlite3AtoF(zDate, &r, sqlite3Strlen30(zDate), SQLITE_UTF8)>0 ){
     setRawDateNumber(p, r);
     return 0;
@@ -946,7 +967,7 @@ static int isDate(
   memset(p, 0, sizeof(*p));
   if( argc==0 ){
     if( !sqlite3NotPureFunc(context) ) return 1;
-    return setDateTimeToCurrent(context, p);
+    return setCurrentStmtTime(context, p);
   }
   if( (eType = sqlite3_value_type(argv[0]))==SQLITE_FLOAT
                    || eType==SQLITE_INTEGER ){

src/sqliteInt.h

@@ -1621,6 +1621,7 @@ struct sqlite3 {
   u8 nSqlExec;                  /* Number of pending OP_SqlExec opcodes */
   u8 eOpenState;                /* Current condition of the connection */
   int nextPagesize;             /* Pagesize after VACUUM if >0 */
+  i64 txnTime;                  /* Timestamp for current transaction */
   i64 nChange;                  /* Value returned by sqlite3_changes() */
   i64 nTotalChange;             /* Value returned by sqlite3_total_changes() */
   int aLimit[SQLITE_N_LIMIT];   /* Limits */
@@ -5341,6 +5342,7 @@ FuncDef *sqlite3VtabOverloadFunction(sqlite3 *,FuncDef*, int nArg, Expr*);
   void sqlite3VtabUsesAllSchemas(sqlite3_index_info*);
 #endif
 sqlite3_int64 sqlite3StmtCurrentTime(sqlite3_context*);
+sqlite3_int64 sqlite3TxnCurrentTime(sqlite3_context*);
 int sqlite3VdbeParameterIndex(Vdbe*, const char*, int);
 int sqlite3TransferBindings(sqlite3_stmt *, sqlite3_stmt *);
 void sqlite3ParseObjectInit(Parse*,sqlite3*);

src/vdbeapi.c

@@ -987,6 +987,29 @@ sqlite3_int64 sqlite3StmtCurrentTime(sqlite3_context *p){
   return *piTime;
 }
 
+/*
+** Return the current time for a transaction.  If the current time
+** is requested more than once within the same transaction
+** the same time is returned for each invocation regardless
+** of the amount of time that elapses between invocations.  In other words,
+** the time returned is always the time of the first call.
+*/
+sqlite3_int64 sqlite3TxnCurrentTime(sqlite3_context *p){
+  int rc;
+#ifndef SQLITE_ENABLE_STAT4
+  sqlite3_int64 *piTime = &p->pVdbe->db->txnTime;
+  assert( p->pVdbe!=0 );
+#else
+  sqlite3_int64 iTime = 0;
+  sqlite3_int64 *piTime = p->pVdbe!=0 ? &p->pVdbe->db->txnTime : &iTime;
+#endif
+  if( *piTime==0 ){
+    rc = sqlite3OsCurrentTimeInt64(p->pOut->db->pVfs, piTime);
+    if( rc ) *piTime = 0;
+  }
+  return *piTime;
+}
+
 /*
 ** Create a new aggregate context for p and return a pointer to
 ** its pMem->z element.

src/vdbeaux.c

@@ -3394,6 +3394,7 @@ int sqlite3VdbeHalt(Vdbe *p){
   */
   if( db->autoCommit ){
     sqlite3ConnectionUnlocked(db);
+    db->txnTime = 0;
   }
 
   assert( db->nVdbeActive>0 || db->autoCommit==0 || db->nStatement==0 );