Update rewriteHandler.cpp

src/gausskernel/optimizer/rewrite/rewriteHandler.cpp

@@ -127,6 +127,15 @@ static bool pull_qual_vars_walker(Node* node, pull_qual_vars_context* context);
  */
 void AcquireRewriteLocks(Query* parsetree, bool forUpdatePushedDown)
 {
+	/*
+	 * @Param[IN] parsetree: A query tree. We need to acquire suitable 
+	 *			locks on all the relations mentioned in the Query.
+	 * @Param[IN] forUpdatePushedDown: Indicates that whether there is a 
+	 *			pushed-down FOR UPDATE/SHARE statement that applies to the 
+	 *			current subquery. It should always be false at the start 
+	 *			of the recursion.
+	 * @Return[OUT]: None.
+	 */
     ListCell* l = NULL;
     int rt_index;
 
@@ -1712,6 +1721,7 @@ static bool fireRIRonSubLink(Node* node, List* activeRIRs)
 /*
  * fireRIRrules -
  *	Apply all RIR rules on each rangetable entry in a query
+ *  
  */
 static Query* fireRIRrules(Query* parsetree, List* activeRIRs, bool forUpdatePushedDown)
 {
@@ -1733,7 +1743,8 @@ static Query* fireRIRrules(Query* parsetree, List* activeRIRs, bool forUpdatePus
         int i;
 
         ++rt_index;
-
+        
+		// fetch RTE of current parsetree node. 
         rte = rt_fetch(rt_index, parsetree->rtable);
 
         /*
@@ -2699,14 +2710,17 @@ static List* RewriteQuery(Query* parsetree, List* rewrite_events)
     return rewritten;
 }
 
+
 /*
- * QueryRewrite -
- *	  Primary entry point to the query rewriter.
- *	  Rewrite one query via query rewrite system, possibly returning 0
- *	  or many queries.
- *
- * NOTE: the parsetree must either have come straight from the parser,
- * or have been scanned by AcquireRewriteLocks to acquire suitable locks.
+ * QueryRewrite()---
+ * 
+ * @Description：Primary entry point to the query rewriter.
+ *	  	Rewrite one query via query rewrite system, possibly returning 0
+ *	  	or many queries.
+ * @Param[IN] parsetree：A Query Tree. It must either have come straight 
+ * 		from the parser, or have been scanned by AcquireRewriteLocks to 
+ *  	acquire suitable locks.
+ * @Return[OUT]： Rewrited queries(0 or several queries).
  */
 List* QueryRewrite(Query* parsetree)
 {
@@ -2722,6 +2736,7 @@ List* QueryRewrite(Query* parsetree)
      * This function is only applied to top-level original queries
      */
     AssertEreport(parsetree->querySource == QSRC_ORIGINAL, MOD_OPT, "");
+    
     AssertEreport(parsetree->canSetTag, MOD_OPT, "");
     /*
      * Step 1
@@ -2733,11 +2748,12 @@ List* QueryRewrite(Query* parsetree)
     /*
      * Step 2
      *
-     * Apply all the RIR rules on each query
+     * Apply all the RIR rules on each query 
      *
      * This is also a handy place to mark each query with the original queryId
      */
     results = NIL;
+    
     foreach (l, querylist) {
         Query* query = (Query*)lfirst(l);
 
@@ -3270,4 +3286,4 @@ List* QueryRewriteCTAS(Query* parsetree)
         }
     }
 }
-#endif
+#endif