From af24481deb31a2bfa1466bfc9d97a26f3bf14208 Mon Sep 17 00:00:00 2001
From: XL_up <3066352084@qq.com>
Date: Mon, 28 Aug 2023 23:11:58 +0800
Subject: [PATCH] Update parser.cpp

---
 src/common/backend/parser/parser.cpp | 36 +++++++++++++++-------------
 1 file changed, 20 insertions(+), 16 deletions(-)

diff --git a/src/common/backend/parser/parser.cpp b/src/common/backend/parser/parser.cpp
index d91fb17cc..d7541e831 100644
--- a/src/common/backend/parser/parser.cpp
+++ b/src/common/backend/parser/parser.cpp
@@ -9,7 +9,6 @@
  * the grammar are "raw" parsetrees that still need to be analyzed by
  * analyze.c and related files.
  *
- *
  * Portions Copyright (c) 1996-2012, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
@@ -40,15 +39,15 @@ static void resetCreateFuncFlag()
 
 /*
  * raw_parser
- *        Given a query in string form, do lexical and grammatical analysis.
+ *		  Given a query in string form, do lexical and grammatical analysis.
  *
  * Returns a list of raw (un-analyzed) parse trees.
  */
 List* raw_parser(const char* str, List** query_string_locationlist)
 {
-    core_yyscan_t yyscanner;
-    base_yy_extra_type yyextra;
-    int yyresult;
+    core_yyscan_t yyscanner;	
+    base_yy_extra_type yyextra;	// An intermediate variable that holds the returned syntax tree.
+    int yyresult;	// The calling result of base_yyparse().
 
     /* reset u_sess->parser_cxt.stmt_contains_operator_plus */
     resetOperatorPlusFlag();
@@ -58,7 +57,7 @@ List* raw_parser(const char* str, List** query_string_locationlist)
 
     /* reset u_sess->parser_cxt.isCreateFuncOrProc */
     resetCreateFuncFlag();
-
+	
     /* initialize the flex scanner */
     yyscanner = scanner_init(str, &yyextra.core_yy_extra, ScanKeywords, NumScanKeywords);
 
@@ -89,6 +88,7 @@ List* raw_parser(const char* str, List** query_string_locationlist)
         }
     }
 
+	// Returns the generated syntax tree.
     return yyextra.parsetree;
 }
 
@@ -127,7 +127,7 @@ List* raw_parser(const char* str, List** query_string_locationlist)
  * words.  Furthermore it's not clear how to do it without re-introducing
  * scanner backtrack, which would cost more performance than this filter
  * layer does.
- *
+ * 
  * The filter also provides a convenient place to translate between
  * the core_YYSTYPE and YYSTYPE representations (which are really the
  * same thing anyway, but notationally they're different).
@@ -489,8 +489,8 @@ int base_yylex(YYSTYPE* lvalp, YYLTYPE* llocp, core_yyscan_t yyscanner)
 
 /*
  * @Description: Check whether its a empty query with only comments and semicolon.
- * @Param query_string: the query need check.
- * @retrun:true or false.
+ * @Param[IN] query_string: the query need check.
+ * @return:the bool value of the check result.
  */
 static bool is_empty_query(char* query_string)
 {
@@ -513,6 +513,7 @@ static bool is_empty_query(char* query_string)
         end_comment_postion = strstr(query_string, end_comment);
         query_string = end_comment_postion + 2;
         while (isspace((unsigned char)*query_string)) {
+        	// Trim the spaces after comments.
             query_string++;
         }
     }
@@ -537,11 +538,12 @@ static bool is_empty_query(char* query_string)
 char** get_next_snippet(
     char** query_string_single, const char* query_string, List* query_string_locationlist, int* stmt_num)
 {
-    int query_string_location_start = 0;
-    int query_string_location_end = -1;
-    char* query_string_single_p = NULL;
-    int single_query_string_len = 0;
-
+    int query_string_location_start = 0;	// The starting position of the query statement.
+    int query_string_location_end = -1;		// The ending position of the query statement.
+    char* query_string_single_p = NULL; 	// An intermediate variable used to copy the string.
+    int single_query_string_len = 0; 		// The length of the query statement.
+    
+	// Count the number of query statements.
     int stmt_count = list_length(query_string_locationlist);
 
     /* Malloc memory for single query here just for the first time. */
@@ -558,11 +560,13 @@ char** get_next_snippet(
          * Notice : The locationlist only store the end postion of each single query but not any
          * start postion.
          */
+        // Calculate the starting position of the specified query statement.
         if (*stmt_num == 0) {
             query_string_location_start = 0;
         } else {
             query_string_location_start = list_nth_int(query_string_locationlist, *stmt_num - 1) + 1;
         }
+        // Calculate the ending position of the specified query statement.
         query_string_location_end = list_nth_int(query_string_locationlist, (*stmt_num)++);
 
         /* Malloc memory for each single query string. */
@@ -583,10 +587,10 @@ char** get_next_snippet(
          */
         if (is_empty_query(query_string_single[*stmt_num - 1])) {
             continue;
-        } else {
+        } else {	// The obtained query statement is not a null query, exit the loop, and return this statement.
             break;
         }
     }
 
     return query_string_single;
-}
+}
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