New ROWIDs are numbered sequentially. (CVS 383)

FossilOrigin-Name: 1686196a8aea326f616bc8205df99cd84d955ec4

4 files changed, 64 insertions, 30 deletions

diff --git a/src/main.c b/src/main.c
index 61450217e..553f74683 100644
--- a/src/main.c
+++ b/src/main.c
@@ -14,7 +14,7 @@
 ** other files are for internal use by SQLite and should not be
 ** accessed by users of the library.
 **
-** $Id: main.c,v 1.59 2002/02/18 18:30:33 drh Exp $
+** $Id: main.c,v 1.60 2002/02/19 22:42:05 drh Exp $
 */
 #include "sqliteInt.h"
 #include "os.h"
@@ -275,8 +275,8 @@ sqlite *sqlite_open(const char *zFilename, int mode, char **pzErrMsg){
   sqliteHashInit(&db->idxHash, SQLITE_HASH_STRING, 0);
   sqliteHashInit(&db->tblDrop, SQLITE_HASH_POINTER, 0);
   sqliteHashInit(&db->idxDrop, SQLITE_HASH_POINTER, 0);
-  db->nextRowid = sqliteRandomInteger();
   db->onError = OE_Default;
+  db->priorNewRowid = 0;
   
   /* Open the backend database driver */
   rc = sqliteBtreeOpen(zFilename, mode, MAX_PAGES, &db->pBe);
diff --git a/src/select.c b/src/select.c
index 036c35ec5..ef6cd216e 100644
--- a/src/select.c
+++ b/src/select.c
@@ -12,7 +12,7 @@
 ** This file contains C code routines that are called by the parser
 ** to handle SELECT statements in SQLite.
 **
-** $Id: select.c,v 1.62 2002/02/19 15:00:08 drh Exp $
+** $Id: select.c,v 1.63 2002/02/19 22:42:05 drh Exp $
 */
 #include "sqliteInt.h"
 
@@ -783,22 +783,28 @@ static int simpleMinMaxQuery(Parse *pParse, Select *p, int eDest, int iParm){
 
   /* Begin generating code
   */
-  base = pParse->nTab;
-  eList.nExpr = 1;
-  memset(&eListItem, 0, sizeof(eListItem));
-  eList.a = &eListItem;
-  eList.a[0].pExpr = pExpr;
+  if( !pParse->schemaVerified && (pParse->db->flags & SQLITE_InTrans)==0 ){
+    sqliteVdbeAddOp(v, OP_VerifyCookie, pParse->db->schema_cookie, 0);
+    pParse->schemaVerified = 1;
+  }
   openOp = pTab->isTemp ? OP_OpenAux : OP_Open;
+  base = pParse->nTab;
   sqliteVdbeAddOp(v, openOp, base, pTab->tnum);
+  sqliteVdbeChangeP3(v, -1, pTab->zName, P3_STATIC);
   if( pIdx==0 ){
     sqliteVdbeAddOp(v, seekOp, base, 0);
   }else{
     sqliteVdbeAddOp(v, openOp, base+1, pIdx->tnum);
+    sqliteVdbeChangeP3(v, -1, pIdx->zName, P3_STATIC);
     sqliteVdbeAddOp(v, seekOp, base+1, 0);
     sqliteVdbeAddOp(v, OP_IdxRecno, base+1, 0);
     sqliteVdbeAddOp(v, OP_Close, base+1, 0);
     sqliteVdbeAddOp(v, OP_MoveTo, base, 0);
   }
+  eList.nExpr = 1;
+  memset(&eListItem, 0, sizeof(eListItem));
+  eList.a = &eListItem;
+  eList.a[0].pExpr = pExpr;
   cont = sqliteVdbeMakeLabel(v);
   selectInnerLoop(pParse, &eList, base, 1, 0, -1, eDest, iParm, cont, cont);
   sqliteVdbeResolveLabel(v, cont);
@@ -1011,6 +1017,7 @@ int sqliteSelect(
   ** in the result set.
   */
   if( simpleMinMaxQuery(pParse, p, eDest, iParm) ){
+    rc = 0;
     goto select_end;
   }
 
diff --git a/src/sqliteInt.h b/src/sqliteInt.h
index 1f3db95bf..302a2b494 100644
--- a/src/sqliteInt.h
+++ b/src/sqliteInt.h
@@ -11,7 +11,7 @@
 *************************************************************************
 ** Internal interface definitions for SQLite.
 **
-** @(#) $Id: sqliteInt.h,v 1.87 2002/02/18 18:30:33 drh Exp $
+** @(#) $Id: sqliteInt.h,v 1.88 2002/02/19 22:42:05 drh Exp $
 */
 #include "sqlite.h"
 #include "hash.h"
@@ -182,7 +182,7 @@ struct sqlite {
   Hash tblDrop;                 /* Uncommitted DROP TABLEs */
   Hash idxDrop;                 /* Uncommitted DROP INDEXs */
   int lastRowid;                /* ROWID of most recent insert */
-  int nextRowid;                /* Next generated rowID */
+  int priorNewRowid;            /* Last randomly generated ROWID */
   int onError;                  /* Default conflict algorithm */
 };
 
diff --git a/src/vdbe.c b/src/vdbe.c
index 788c5a9d2..f9f088504 100644
--- a/src/vdbe.c
+++ b/src/vdbe.c
@@ -30,7 +30,7 @@
 ** But other routines are also provided to help in building up
 ** a program instruction by instruction.
 **
-** $Id: vdbe.c,v 1.119 2002/02/19 15:00:08 drh Exp $
+** $Id: vdbe.c,v 1.120 2002/02/19 22:42:05 drh Exp $
 */
 #include "sqliteInt.h"
 #include <ctype.h>
@@ -71,6 +71,7 @@ struct Cursor {
   Bool recnoIsValid;    /* True if lastRecno is valid */
   Bool keyAsData;       /* The OP_Column command works on key instead of data */
   Bool atFirst;         /* True if pointing to first entry */
+  Bool useRandomRowid;  /* Generate new record numbers semi-randomly */
   Btree *pBt;           /* Separate file holding temporary table */
 };
 typedef struct Cursor Cursor;
@@ -2913,10 +2914,18 @@ case OP_NewRecno: {
   if( VERIFY( i<0 || i>=p->nCursor || ) (pC = &p->aCsr[i])->pCursor==0 ){
     v = 0;
   }else{
-    /* A probablistic algorithm is used to locate an unused rowid.
-    ** We select a rowid at random and see if it exists in the table.
-    ** If it does not exist, we have succeeded.  If the random rowid
-    ** does exist, we select a new one and try again, up to 1000 times.
+    /* The next rowid or record number (different terms for the same
+    ** thing) is obtained in a two-step algorithm.
+    **
+    ** First we attempt to find the largest existing rowid and add one
+    ** to that.  But if the largest existing rowid is already the maximum
+    ** positive integer, we have to fall through to the second
+    ** probabilistic algorithm
+    **
+    ** The second algorithm is to select a rowid at random and see if
+    ** it already exists in the table.  If it does not exist, we have
+    ** succeeded.  If the random rowid does exist, we select a new one
+    ** and try again, up to 1000 times.
     **
     ** For a table with less than 2 billion entries, the probability
     ** of not finding a unused rowid is about 1.0e-300.  This is a 
@@ -2932,28 +2941,46 @@ case OP_NewRecno: {
     ** random number generator based on the RC4 algorithm.
     **
     ** To promote locality of reference for repetitive inserts, the
-    ** first few attempts at chosing a rowid pick values just a little
+    ** first few attempts at chosing a random rowid pick values just a little
     ** larger than the previous rowid.  This has been shown experimentally
     ** to double the speed of the COPY operation.
     */
     int res, rx, cnt, x;
     cnt = 0;
-    v = db->nextRowid;
-    do{
-      if( cnt>5 ){
-        v = sqliteRandomInteger();
+    if( !pC->useRandomRowid ){
+      rx = sqliteBtreeLast(pC->pCursor, &res);
+      if( res ){
+        v = 1;
       }else{
-        v += sqliteRandomByte() + 1;
+        sqliteBtreeKey(pC->pCursor, 0, sizeof(v), (void*)&v);
+        v = keyToInt(v);
+        if( v==0x7fffffff ){
+          pC->useRandomRowid = 1;
+        }else{
+          v++;
+        }
+      }
+    }
+    if( pC->useRandomRowid ){
+      v = db->priorNewRowid;
+      cnt = 0;
+      do{
+        if( v==0 || cnt>2 ){
+          v = sqliteRandomInteger();
+          if( cnt<5 ) v &= 0xffffff;
+        }else{
+          v += sqliteRandomByte() + 1;
+        }
+        if( v==0 ) continue;
+        x = intToKey(v);
+        rx = sqliteBtreeMoveto(pC->pCursor, &x, sizeof(int), &res);
+        cnt++;
+      }while( cnt<1000 && rx==SQLITE_OK && res==0 );
+      db->priorNewRowid = v;
+      if( rx==SQLITE_OK && res==0 ){
+        rc = SQLITE_FULL;
+        goto abort_due_to_error;
       }
-      if( v==0 ) continue;
-      x = intToKey(v);
-      rx = sqliteBtreeMoveto(pC->pCursor, &x, sizeof(int), &res);
-      cnt++;
-    }while( cnt<1000 && rx==SQLITE_OK && res==0 );
-    db->nextRowid = v;
-    if( rx==SQLITE_OK && res==0 ){
-      rc = SQLITE_FULL;
-      goto abort_due_to_error;
     }
   }
   VERIFY( NeedStack(p, p->tos+1); )