1 files changed, 9 insertions, 0 deletions
diff --git a/src/where.c b/src/where.c
index 1d8ba88ba..79ec7f690 100644
--- a/src/where.c
+++ b/src/where.c
@@ -5353,6 +5353,15 @@ static int wherePathSolver(WhereInfo *pWInfo, LogEst nRowEst){
 
   pWInfo->nRowOut = pFrom->nRow;
 
+  /* TUNING:  Assume that a DISTINCT clause on a subquery reduces
+  ** the output size by a factor of 8 (LogEst -30)
+  */
+  if( (pWInfo->wctrlFlags & WHERE_WANT_DISTINCT)!=0
+   && pWInfo->nRowOut>30
+  ){
+    pWInfo->nRowOut -= 30;
+  }
+
   /* Free temporary memory and return success */
   sqlite3StackFreeNN(pParse->db, pSpace);
   return SQLITE_OK;