Fix the OP_OpenEphemeral opcode in the bytecode engine so that if it is called

a second or subsequent time, it merely clears the existing table rather than
creating a new one.  Proposed fix for ticket [d0866b26f83e9c55e30de0821f5d].

FossilOrigin-Name: 4678cb1044f0b4dc813e48f3bd0f85240a66e2ecf8763280d66726cc031c93a7

1 files changed, 16 insertions, 4 deletions

diff --git a/src/vdbe.c b/src/vdbe.c
index 26382bcd4..1f4d569ae 100644
--- a/src/vdbe.c
+++ b/src/vdbe.c
@@ -3628,6 +3628,9 @@ case OP_OpenDup: {
 ** the main database is read-only.  The ephemeral
 ** table is deleted automatically when the cursor is closed.
 **
+** If the cursor P1 is already opened on an ephermal table, the table
+** is cleared (all content is erased).
+**
 ** P2 is the number of columns in the ephemeral table.
 ** The cursor points to a BTree table if P4==0 and to a BTree index
 ** if P4 is not 0.  If P4 is not NULL, it points to a KeyInfo structure
@@ -3659,6 +3662,14 @@ case OP_OpenEphemeral: {
       SQLITE_OPEN_TRANSIENT_DB;
   assert( pOp->p1>=0 );
   assert( pOp->p2>=0 );
+  pCx = p->apCsr[pOp->p1];
+  if( pCx ){
+    /* If the ephermeral table is already open, erase all existing content
+    ** so that the table is empty again, rather than creating a new table. */
+    rc = sqlite3BtreeClearTable(pCx->pBtx, pCx->pgnoRoot, 0);
+    if( rc ) goto abort_due_to_error;
+    break;
+  }
   pCx = allocateCursor(p, pOp->p1, pOp->p2, -1, CURTYPE_BTREE);
   if( pCx==0 ) goto no_mem;
   pCx->nullRow = 1;
@@ -3675,18 +3686,19 @@ case OP_OpenEphemeral: {
     ** automatically created table with root-page 1 (an BLOB_INTKEY table).
     */
     if( (pCx->pKeyInfo = pKeyInfo = pOp->p4.pKeyInfo)!=0 ){
-      int pgno;
       assert( pOp->p4type==P4_KEYINFO );
-      rc = sqlite3BtreeCreateTable(pCx->pBtx, &pgno, BTREE_BLOBKEY | pOp->p5); 
+      rc = sqlite3BtreeCreateTable(pCx->pBtx, (int*)&pCx->pgnoRoot,
+                                   BTREE_BLOBKEY | pOp->p5); 
       if( rc==SQLITE_OK ){
-        assert( pgno==MASTER_ROOT+1 );
+        assert( pCx->pgnoRoot==MASTER_ROOT+1 );
         assert( pKeyInfo->db==db );
         assert( pKeyInfo->enc==ENC(db) );
-        rc = sqlite3BtreeCursor(pCx->pBtx, pgno, BTREE_WRCSR,
+        rc = sqlite3BtreeCursor(pCx->pBtx, pCx->pgnoRoot, BTREE_WRCSR,
                                 pKeyInfo, pCx->uc.pCursor);
       }
       pCx->isTable = 0;
     }else{
+      pCx->pgnoRoot = MASTER_ROOT;
       rc = sqlite3BtreeCursor(pCx->pBtx, MASTER_ROOT, BTREE_WRCSR,
                               0, pCx->uc.pCursor);
       pCx->isTable = 1;