Index: src/expr.c
==================================================================
--- src/expr.c
+++ src/expr.c
@@ -2227,10 +2227,15 @@
           if( aiMap ) aiMap[i] = j;
         }
 
         if( i==nExpr ){
           int iAddr = sqlite3CodeOnce(pParse); VdbeCoverage(v);
+#ifndef SQLITE_OMIT_EXPLAIN
+          sqlite3VdbeAddOp4(v, OP_Explain, 0, 0, 0,
+            sqlite3MPrintf(db, "USING INDEX %s FOR IN-OPERATOR", pIdx->zName),
+            P4_DYNAMIC);
+#endif
           sqlite3VdbeAddOp3(v, OP_OpenRead, iTab, pIdx->tnum, iDb);
           sqlite3VdbeSetP4KeyInfo(pParse, pIdx);
           VdbeComment((v, "%s", pIdx->zName));
           assert( IN_INDEX_INDEX_DESC == IN_INDEX_INDEX_ASC+1 );
           eType = IN_INDEX_INDEX_ASC + pIdx->aSortOrder[0];