增加show variables like var_string语法，方便用户查询参数时，记不清变量名称时使用

src/common/backend/parser/gram.y

@@ -697,7 +697,7 @@ static void ParseUpdateMultiSet(List *set_target_list, SelectStmt *stmt, core_yy
 	UNBOUNDED UNCOMMITTED UNENCRYPTED UNION UNIQUE UNKNOWN UNLIMITED UNLISTEN UNLOCK UNLOGGED
 	UNTIL UNUSABLE UPDATE USER USING
 
-	VACUUM VALID VALIDATE VALIDATION VALIDATOR VALUE_P VALUES VARCHAR VARCHAR2 VARIADIC VARRAY VARYING VCGROUP
+	VACUUM VALID VALIDATE VALIDATION VALIDATOR VALUE_P VALUES VARCHAR VARCHAR2 VARIABLES VARIADIC VARRAY VARYING VCGROUP
 	VERBOSE VERIFY VERSION_P VIEW VOLATILE
 
 	WHEN WHERE WHITESPACE_P WINDOW WITH WITHIN WITHOUT WORK WORKLOAD WRAPPER WRITE
@@ -2073,6 +2073,13 @@ VariableShowStmt:
 					n->name = "session_authorization";
 					$$ = (Node *) n;
 				}
+			| SHOW VARIABLES LIKE var_name
+				{
+					VariableShowStmt *n = makeNode(VariableShowStmt);
+					n->name = "all";
+					n->likename = $4;
+					$$ =(Node *) n;
+				}
 			| SHOW ALL
 				{
 					VariableShowStmt *n = makeNode(VariableShowStmt);

src/common/backend/utils/misc/guc.cpp

@@ -12278,7 +12278,7 @@ static void report_guc_option(struct config_generic* record);
 static void reapply_stacked_values(struct config_generic* variable, struct config_string* holder, GucStack* stack,
     const char* curvalue, GucContext curscontext, GucSource cursource);
 static void show_guc_config_option(const char* name, DestReceiver* dest);
-static void show_all_guc_config(DestReceiver* dest);
+static void show_all_guc_config(const char* likename, DestReceiver* dest);
 static char* _show_option(struct config_generic* record, bool use_units);
 static bool validate_option_array_item(const char* name, const char* value, bool skip_if_no_permissions);
 static void replace_config_value(char** optlines, char* name, char* value, config_type vartype);
@@ -16898,10 +16898,10 @@ void EmitWarningsOnPlaceholders(const char* className)
 /*
  * SHOW command
  */
-void GetPGVariable(const char* name, DestReceiver* dest)
+void GetPGVariable(const char* name, const char* likename, DestReceiver* dest)
 {
     if (guc_name_compare(name, "all") == 0) {
-        show_all_guc_config(dest);
+        show_all_guc_config(likename, dest);
     } else {
         show_guc_config_option(name, dest);
     }
@@ -16960,7 +16960,7 @@ static void show_guc_config_option(const char* name, DestReceiver* dest)
 /*
  * SHOW ALL command
  */
-static void show_all_guc_config(DestReceiver* dest)
+static void show_all_guc_config(const char* likename, DestReceiver* dest)
 {
     bool am_superuser = (GetUserId() == BOOTSTRAP_SUPERUSERID);
     int i;
@@ -16968,6 +16968,7 @@ static void show_all_guc_config(DestReceiver* dest)
     TupleDesc tupdesc;
     Datum values[3];
     bool isnull[3] = {false, false, false};
+    char* ptr;
 
     /* need a tuple descriptor representing three TEXT columns */
     tupdesc = CreateTemplateTupleDesc(3, false);
@@ -16986,6 +16987,13 @@ static void show_all_guc_config(DestReceiver* dest)
             continue;
         }
 
+        if(NULL != likename) {
+            ptr = strstr((char*)conf->name, likename);
+            if (NULL == ptr) {
+                continue;
+            }
+        }
+
         /* assign to the values array */
         values[0] = PointerGetDatum(cstring_to_text(conf->name));
 

src/gausskernel/process/tcop/utility.cpp

@@ -4892,7 +4892,7 @@ void standard_ProcessUtility(Node* parse_tree, const char* query_string, ParamLi
         case T_VariableShowStmt: {
             VariableShowStmt* n = (VariableShowStmt*)parse_tree;
 
-            GetPGVariable(n->name, dest);
+            GetPGVariable(n->name, n->likename, dest);
         } break;
         case T_ShutdownStmt: {
             ShutdownStmt* n = (ShutdownStmt*)parse_tree;

src/include/nodes/parsenodes.h

@@ -1783,6 +1783,7 @@ typedef struct VariableSetStmt {
 typedef struct VariableShowStmt {
     NodeTag type;
     char* name;
+    char* likename;
 } VariableShowStmt;
 
 /* ----------------------

src/include/parser/kwlist.h

@@ -547,6 +547,7 @@ PG_KEYWORD("value", VALUE_P, UNRESERVED_KEYWORD)
 PG_KEYWORD("values", VALUES, COL_NAME_KEYWORD)
 PG_KEYWORD("varchar", VARCHAR, COL_NAME_KEYWORD)
 PG_KEYWORD("varchar2", VARCHAR2, COL_NAME_KEYWORD)
+PG_KEYWORD("variables", VARIABLES, UNRESERVED_KEYWORD)
 PG_KEYWORD("variadic", VARIADIC, RESERVED_KEYWORD)
 PG_KEYWORD("varying", VARYING, UNRESERVED_KEYWORD)
 PG_KEYWORD("vcgroup", VCGROUP, UNRESERVED_KEYWORD)

src/include/utils/guc.h

@@ -251,7 +251,7 @@ extern void GetConfigOptionByNum(int varnum, const char** values, bool* noshow);
 extern int GetNumConfigOptions(void);
 
 extern void SetPGVariable(const char* name, List* args, bool is_local);
-extern void GetPGVariable(const char* name, DestReceiver* dest);
+extern void GetPGVariable(const char* name, const char* likename, DestReceiver* dest);
 extern TupleDesc GetPGVariableResultDesc(const char* name);
 
 #ifdef PGXC