Show LEFT and RIGHT JOIN processing in the EXPLAIN QUERY PLAN output.

FossilOrigin-Name: d91faeffea5cf0585fb71e5311fdcc6b8be85c7e9c732050b4448e617c970101

3 files changed, 12 insertions, 7 deletions

diff --git a/src/sqliteInt.h b/src/sqliteInt.h
index b9eb970c7..330d58fa4 100644
--- a/src/sqliteInt.h
+++ b/src/sqliteInt.h
@@ -3163,7 +3163,7 @@ struct SrcList {
 #define WHERE_SORTBYGROUP      0x0200 /* Support sqlite3WhereIsSorted() */
 #define WHERE_AGG_DISTINCT     0x0400 /* Query is "SELECT agg(DISTINCT ...)" */
 #define WHERE_ORDERBY_LIMIT    0x0800 /* ORDERBY+LIMIT on the inner loop */
-                        /*     0x1000    not currently used */
+#define WHERE_RIGHT_JOIN       0x1000 /* Processing a RIGHT JOIN */
                         /*     0x2000    not currently used */
 #define WHERE_USE_LIMIT        0x4000 /* Use the LIMIT in cost estimates */
                         /*     0x8000    not currently used */
diff --git a/src/where.c b/src/where.c
index 1cd8f4ded..3677759ce 100644
--- a/src/where.c
+++ b/src/where.c
@@ -6191,8 +6191,9 @@ void sqlite3WhereEnd(WhereInfo *pWInfo){
       sFrom.nAlloc = 1;
       memcpy(&sFrom.a[0], pTabItem, sizeof(SrcItem));
       sFrom.a[0].fg.jointype = 0;
+      ExplainQueryPlan((pParse, 1, "RIGHT-JOIN %s", pTab->zName));
       pSubWInfo = sqlite3WhereBegin(pParse, &sFrom, pSubWhere, 0, 0, 0,
-                                    WHERE_OR_SUBCLAUSE, 0);
+                                    WHERE_RIGHT_JOIN, 0);
       if( pSubWInfo ){
         int iCur = pLevel->iTabCur;
         int r = ++pParse->nMem;
@@ -6219,6 +6220,7 @@ void sqlite3WhereEnd(WhereInfo *pWInfo){
         sqlite3WhereEnd(pSubWInfo);
       }
       sqlite3ExprDelete(pParse->db, pSubWhere);
+      ExplainQueryPlanPop(pParse);
       continue;
     }
 
diff --git a/src/wherecode.c b/src/wherecode.c
index 0c8104867..410d6f206 100644
--- a/src/wherecode.c
+++ b/src/wherecode.c
@@ -204,6 +204,9 @@ int sqlite3WhereExplainOneScan(
                   pLoop->u.vtab.idxNum, pLoop->u.vtab.idxStr);
     }
 #endif
+    if( pItem->fg.jointype & JT_LEFT ){
+      sqlite3_str_appendf(&str, " LEFT-JOIN");
+    }
 #ifdef SQLITE_EXPLAIN_ESTIMATED_ROWS
     if( pLoop->nOut>=10 ){
       sqlite3_str_appendf(&str, " (~%llu rows)",
@@ -1150,7 +1153,7 @@ static void codeDeferredSeek(
   
   pWInfo->bDeferredSeek = 1;
   sqlite3VdbeAddOp3(v, OP_DeferredSeek, iIdxCur, 0, iCur);
-  if( (pWInfo->wctrlFlags & WHERE_OR_SUBCLAUSE)
+  if( (pWInfo->wctrlFlags & (WHERE_OR_SUBCLAUSE|WHERE_RIGHT_JOIN))
    && DbMaskAllZero(sqlite3ParseToplevel(pParse)->writeMask)
   ){
     int i;
@@ -1502,7 +1505,7 @@ Bitmask sqlite3WhereCodeOneLoopStart(
   ** initialize a memory cell that records if this table matches any
   ** row of the left table of the join.
   */
-  assert( (pWInfo->wctrlFlags & WHERE_OR_SUBCLAUSE)
+  assert( (pWInfo->wctrlFlags & (WHERE_OR_SUBCLAUSE|WHERE_RIGHT_JOIN))
        || pLevel->iFrom>0 || (pTabItem[0].fg.jointype & JT_LEFT)==0
   );
   if( pLevel->iFrom>0 && (pTabItem[0].fg.jointype & JT_LEFT)!=0 ){
@@ -2140,7 +2143,7 @@ Bitmask sqlite3WhereCodeOneLoopStart(
 
     /* Seek the table cursor, if required */
     omitTable = (pLoop->wsFlags & WHERE_IDX_ONLY)!=0 
-           && (pWInfo->wctrlFlags & WHERE_OR_SUBCLAUSE)==0;
+           && (pWInfo->wctrlFlags & (WHERE_OR_SUBCLAUSE|WHERE_RIGHT_JOIN))==0;
     if( omitTable ){
       /* pIdx is a covering index.  No need to access the main table. */
     }else if( HasRowid(pIdx->pTable) ){
@@ -2174,7 +2177,7 @@ Bitmask sqlite3WhereCodeOneLoopStart(
       ** move forward to the next index.
       ** https://sqlite.org/src/info/4e8e4857d32d401f
       */
-      if( (pWInfo->wctrlFlags & WHERE_OR_SUBCLAUSE)==0 ){
+      if( (pWInfo->wctrlFlags & (WHERE_OR_SUBCLAUSE|WHERE_RIGHT_JOIN))==0 ){
         whereIndexExprTrans(pIdx, iCur, iIdxCur, pWInfo);
       }
   
@@ -2193,7 +2196,7 @@ Bitmask sqlite3WhereCodeOneLoopStart(
       /* The following assert() is not a requirement, merely an observation:
       ** The OR-optimization doesn't work for the right hand table of
       ** a LEFT JOIN: */
-      assert( (pWInfo->wctrlFlags & WHERE_OR_SUBCLAUSE)==0 );
+      assert( (pWInfo->wctrlFlags & (WHERE_OR_SUBCLAUSE|WHERE_RIGHT_JOIN))==0 );
     }
   
     /* Record the instruction used to terminate the loop. */