Bug#28497 wait_for_slave_to_stop can cause random replication mysql-test failures

 - Add funtion "query_get_value to allow reading a fields value
   into a $variable


client/mysqltest.c:
  - Add function "let $var= query_get_value(<query>,<colname>,<row>)"
    making it possible to read a value from a specific field in a query 
    into a $variable.
mysql-test/r/mysqltest.result:
  Add test cases for "query_get_value"
mysql-test/t/mysqltest.test:
  Add test cases for "query_get_value"

client/mysqltest.c

@@ -1125,6 +1125,50 @@ void check_require(DYNAMIC_STRING* ds, const char *fname)
 }
 
 
+/*
+   Remove surrounding chars from string
+
+   Return 1 if first character is found but not last
+*/
+static int strip_surrounding(char* str, char c1, char c2)
+{
+  char* ptr= str;
+
+  /* Check if the first non space character is c1 */
+  while(*ptr && my_isspace(charset_info, *ptr))
+    ptr++;
+  if (*ptr == c1)
+  {
+    /* Replace it with a space */
+    *ptr= ' ';
+
+    /* Last non space charecter should be c2 */
+    ptr= strend(str)-1;
+    while(*ptr && my_isspace(charset_info, *ptr))
+      ptr--;
+    if (*ptr == c2)
+    {
+      /* Replace it with \0 */
+      *ptr= 0;
+    }
+    else
+    {
+      /* Mismatch detected */
+      return 1;
+    }
+  }
+  return 0;
+}
+
+
+static void strip_parentheses(struct st_command *command)
+{
+  if (strip_surrounding(command->first_argument, '(', ')'))
+      die("%.*s - argument list started with '%c' must be ended with '%c'",
+          command->first_word_len, command->query, '(', ')');
+}
+
+
 static byte *get_var_key(const byte* var, uint* len,
                   my_bool __attribute__((unused)) t)
 {
@@ -1380,12 +1424,11 @@ void var_query_set(VAR *var, const char *query, const char** query_end)
   init_dynamic_string(&ds_query, 0, (end - query) + 32, 256);
   do_eval(&ds_query, query, end, FALSE);
 
-  if (mysql_real_query(mysql, ds_query.str, ds_query.length) ||
-      !(res = mysql_store_result(mysql)))
-  {
+  if (mysql_real_query(mysql, ds_query.str, ds_query.length))
     die("Error running query '%s': %d %s", ds_query.str,
 	mysql_errno(mysql), mysql_error(mysql));
-  }
+  if (!(res= mysql_store_result(mysql)))
+    die("Query '%s' didn't return a result set", ds_query.str);
   dynstr_free(&ds_query);
 
   if ((row = mysql_fetch_row(res)) && row[0])
@@ -1440,6 +1483,130 @@ void var_query_set(VAR *var, const char *query, const char** query_end)
 }
 
 
+/*
+  Set variable from the result of a field in a query
+
+  This function is useful when checking for a certain value
+  in the output from a query that can't be restricted to only
+  return some values. A very good example of that is most SHOW
+  commands.
+
+  SYNOPSIS
+  var_set_query_get_value()
+
+  DESCRIPTION
+  let $variable= query_get_value(<query to run>,<column name>,<row no>);
+
+  <query to run> -    The query that should be sent to the server
+  <column name> -     Name of the column that holds the field be compared
+                      against the expected value
+  <row no> -          Number of the row that holds the field to be
+                      compared against the expected value
+
+*/
+
+void var_set_query_get_value(struct st_command *command, VAR *var)
+{
+  ulong row_no;
+  int col_no= -1;
+  MYSQL_RES* res;
+  MYSQL* mysql= &cur_con->mysql;
+  LINT_INIT(res);
+
+  static DYNAMIC_STRING ds_query;
+  static DYNAMIC_STRING ds_col;
+  static DYNAMIC_STRING ds_row;
+  const struct command_arg query_get_value_args[] = {
+    "query", ARG_STRING, TRUE, &ds_query, "Query to run",
+    "column name", ARG_STRING, TRUE, &ds_col, "Name of column",
+    "row number", ARG_STRING, TRUE, &ds_row, "Number for row",
+  };
+
+  DBUG_ENTER("var_set_query_get_value");
+
+  strip_parentheses(command);
+  DBUG_PRINT("info", ("query: %s", command->query));
+  check_command_args(command, command->first_argument, query_get_value_args,
+                     sizeof(query_get_value_args)/sizeof(struct command_arg),
+                     ',');
+
+  DBUG_PRINT("info", ("query: %s", ds_query.str));
+  DBUG_PRINT("info", ("col: %s", ds_col.str));
+
+  /* Convert row number to int */
+  if (!str2int(ds_row.str, 10, (long) 0, (long) INT_MAX, &row_no))
+    die("Invalid row number: '%s'", ds_row.str);
+  DBUG_PRINT("info", ("row: %s, row_no: %ld", ds_row.str, row_no));
+  dynstr_free(&ds_row);
+
+  /* Remove any surrounding "'s from the query - if there is any */
+  if (strip_surrounding(ds_query.str, '"', '"'))
+    die("Mismatched \"'s around query '%s'", ds_query.str);
+
+  /* Run the query */
+  if (mysql_real_query(mysql, ds_query.str, ds_query.length))
+    die("Error running query '%s': %d %s", ds_query.str,
+	mysql_errno(mysql), mysql_error(mysql));
+  if (!(res= mysql_store_result(mysql)))
+    die("Query '%s' didn't return a result set", ds_query.str);
+
+  {
+    /* Find column number from the given column name */
+    uint i;
+    uint num_fields= mysql_num_fields(res);
+    MYSQL_FIELD *fields= mysql_fetch_fields(res);
+
+    for (i= 0; i < num_fields; i++)
+    {
+      if (strcmp(fields[i].name, ds_col.str) == 0 &&
+          strlen(fields[i].name) == ds_col.length)
+      {
+        col_no= i;
+        break;
+      }
+    }
+    if (col_no == -1)
+    {
+      mysql_free_result(res);
+      die("Could not find column '%s' in the result of '%s'",
+          ds_col.str, ds_query.str);
+    }
+    DBUG_PRINT("info", ("Found column %d with name '%s'",
+                        i, fields[i].name));
+  }
+  dynstr_free(&ds_col);
+
+  {
+    /* Get the value */
+    MYSQL_ROW row;
+    ulong rows= 0;
+    const char* value= "No such row";
+
+    while ((row= mysql_fetch_row(res)))
+    {
+      if (++rows == row_no)
+      {
+
+        DBUG_PRINT("info", ("At row %ld, column %d is '%s'",
+                            row_no, col_no, row[col_no]));
+        /* Found the row to get */
+        if (row[col_no])
+          value= row[col_no];
+        else
+          value= "NULL";
+
+        break;
+      }
+    }
+    eval_expr(var, value, 0);
+  }
+  dynstr_free(&ds_query);
+  mysql_free_result(res);
+
+  DBUG_VOID_RETURN;
+}
+
+
 void var_copy(VAR *dest, VAR *src)
 {
   dest->int_val= src->int_val;
@@ -1463,26 +1630,47 @@ void var_copy(VAR *dest, VAR *src)
 
 void eval_expr(VAR *v, const char *p, const char **p_end)
 {
-  static int MIN_VAR_ALLOC= 32; /* MASV why 32? */
-  VAR *vp;
+
+  DBUG_ENTER("eval_expr");
+  DBUG_PRINT("enter", ("p: '%s'", p));
+
   if (*p == '$')
   {
+    VAR *vp;
     if ((vp= var_get(p, p_end, 0, 0)))
-    {
       var_copy(v, vp);
-      return;
-    }
+    DBUG_VOID_RETURN;
   }
-  else if (*p == '`')
+
+  if (*p == '`')
   {
     var_query_set(v, p, p_end);
+    DBUG_VOID_RETURN;
   }
-  else
+
+  {
+    /* Check if this is a "let $var= query_get_value()" */
+    const char* get_value_str= "query_get_value";
+    const size_t len= strlen(get_value_str);
+    if (strncmp(p, get_value_str, len)==0)
+    {
+      struct st_command command;
+      memset(&command, 0, sizeof(command));
+      command.query= (char*)p;
+      command.first_word_len= len;
+      command.first_argument= command.query + len;
+      command.end= (char*)*p_end;
+      var_set_query_get_value(&command, v);
+      DBUG_VOID_RETURN;
+    }
+  }
+
   {
     int new_val_len = (p_end && *p_end) ?
       (int) (*p_end - p) : (int) strlen(p);
     if (new_val_len + 1 >= v->alloced_len)
     {
+      static int MIN_VAR_ALLOC= 32;
       v->alloced_len = (new_val_len < MIN_VAR_ALLOC - 1) ?
         MIN_VAR_ALLOC : new_val_len + 1;
       if (!(v->str_val =
@@ -1495,9 +1683,10 @@ void eval_expr(VAR *v, const char *p, const char **p_end)
     memcpy(v->str_val, p, new_val_len);
     v->str_val[new_val_len] = 0;
     v->int_val=atoi(p);
+    DBUG_PRINT("info", ("atoi on '%s', returns: %d", p, v->int_val));
     v->int_dirty=0;
   }
-  return;
+  DBUG_VOID_RETURN;
 }
 
 
@@ -3432,7 +3621,6 @@ void do_connect(struct st_command *command)
   int con_port= port;
   char *con_options;
   bool con_ssl= 0, con_compress= 0;
-  char *ptr;
 
   static DYNAMIC_STRING ds_connection_name;
   static DYNAMIC_STRING ds_host;
@@ -3460,20 +3648,7 @@ void do_connect(struct st_command *command)
   DBUG_ENTER("do_connect");
   DBUG_PRINT("enter",("connect: %s", command->first_argument));
 
-  /* Remove parenteses around connect arguments */
-  if ((ptr= strstr(command->first_argument, "(")))
-  {
-    /* Replace it with a space */
-    *ptr= ' ';
-    if ((ptr= strstr(command->first_argument, ")")))
-    {
-      /* Replace it with \0 */
-      *ptr= 0;
-    }
-    else
-      die("connect - argument list started with '(' must be ended with ')'");
-  }
-
+  strip_parentheses(command);
   check_command_args(command, command->first_argument, connect_args,
                      sizeof(connect_args)/sizeof(struct command_arg),
                      ',');
@@ -4173,16 +4348,12 @@ int read_command(struct st_command** command_ptr)
     DBUG_RETURN(0);
   }
   if (!(*command_ptr= command=
-        (struct st_command*) my_malloc(sizeof(*command), MYF(MY_WME))) ||
+        (struct st_command*) my_malloc(sizeof(*command),
+                                       MYF(MY_WME|MY_ZEROFILL))) ||
       insert_dynamic(&q_lines, (gptr) &command))
     die(NullS);
-
-  command->require_file[0]= 0;
-  command->first_word_len= 0;
-  command->query_len= 0;
-
   command->type= Q_UNKNOWN;
-  command->query_buf= command->query= 0;
+
   read_command_buf[0]= 0;
   if (read_line(read_command_buf, sizeof(read_command_buf)))
   {

mysql-test/r/mysqltest.result

@@ -655,4 +655,43 @@ INSERT INTO t1 SELECT f1 - 256 FROM t1;
 INSERT INTO t1 SELECT f1 - 512 FROM t1;
 SELECT * FROM t1;
 DROP TABLE t1;
+CREATE TABLE t1(
+a int, b varchar(255), c datetime
+);
+SHOW COLUMNS FROM t1;
+Field	Type	Null	Key	Default	Extra
+a	int(11)	YES		NULL	
+b	varchar(255)	YES		NULL	
+c	datetime	YES		NULL	
+statement=SHOW COLUMNS FROM t1 row_number=1, column_name="Type", Value=int(11)
+statement="SHOW COLUMNS FROM t1" row_number=1, column_name="Type", Value=int(11)
+statement=SHOW COLUMNS FROM t1 row_number=1, column_name=Default, Value=NULL
+value= ->A B<-
+value= 1
+mysqltest: At line 1: query_get_value - argument list started with '(' must be ended with ')'
+mysqltest: At line 1: Missing required argument 'query' to command 'query_get_value'
+mysqltest: At line 1: Missing required argument 'column name' to command 'query_get_value'
+mysqltest: At line 1: Missing required argument 'row number' to command 'query_get_value'
+value= No such row
+value= No such row
+mysqltest: At line 1: Invalid row number: 'notnumber'
+mysqltest: At line 1: Could not find column 'column_not_exists' in the result of 'SHOW COLUMNS FROM t1'
+mysqltest: At line 1: Query 'SET @A = 1' didn't return a result set
+mysqltest: At line 1: Could not find column '1 AS B' in the result of 'SELECT 1 AS A'
+value= No such row
+mysqltest: At line 1: Error running query 'SHOW COLNS FROM t1': 1064 You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'COLNS FROM t1' at line 1
+
+Field Type Null Key Default Extra
+a int(11) YES -><- NULL 
+b varchar(255) YES -><- NULL 
+c datetime YES -><- NULL 
+
+Number of columns with Default NULL: 3
+
+SHOW COLUMNS FROM t1;
+Field	Type	Null	Key	Default	Extra
+a	int(11)	YES		NULL	
+b	varchar(255)	YES		NULL	
+c	datetime	YES		NULL	
+drop table t1;
 End of tests

mysql-test/t/mysqltest.test

@@ -1811,4 +1811,125 @@ SELECT * FROM t1;
 --enable_result_log
 DROP TABLE t1;
 
+# ----------------------------------------------------------------------------
+# test for query_get_value
+# ----------------------------------------------------------------------------
+
+CREATE TABLE t1(
+ a int, b varchar(255), c datetime
+);
+SHOW COLUMNS FROM t1;
+
+#------------ Positive tests ------------
+# 1. constant parameters
+#    value is simple string without spaces
+let $value= query_get_value(SHOW COLUMNS FROM t1, Type, 1);
+--echo statement=SHOW COLUMNS FROM t1 row_number=1, column_name="Type", Value=$value
+let $value= query_get_value("SHOW COLUMNS FROM t1", Type, 1);
+--echo statement="SHOW COLUMNS FROM t1" row_number=1, column_name="Type", Value=$value
+#
+# 2. $variables as parameters
+#    value IS NULL
+let $my_show= SHOW COLUMNS FROM t1;
+let $column_name= Default;
+let $row_number= 1;
+let $value= query_get_value($my_show, $column_name, $row_number);
+--echo statement=$my_show row_number=$row_number, column_name=$column_name, Value=$value
+#
+# 3. result set of a SELECT (not recommended, because projection and
+#         selection could be done much better by pure SELECT functionality)
+#    value is string with space in the middle
+let $value= query_get_value(SELECT 'A B' AS "MyColumn", MyColumn, 1);
+--echo value= ->$value<-
+#
+# 4. column name with space
+let $value= query_get_value(SELECT 1 AS "My Column", My Column, 1);
+--echo value= $value
+#
+#------------ Negative tests ------------
+# 5. Incomplete statement including missing parameters
+# 5.1 incomplete statement
+--error 1
+--exec echo "let \$value= query_get_value(SHOW;" | $MYSQL_TEST 2>&1
+# 5.2 missing query
+--error 1
+--exec echo "let \$value= query_get_value;" | $MYSQL_TEST 2>&1
+# 5.3 missing column name
+--error 1
+--exec echo "let \$value= query_get_value(SHOW COLUMNS FROM t1);" | $MYSQL_TEST 2>&1
+# 5.4 missing row number
+--error 1
+--exec echo "let \$value= query_get_value(SHOW COLUMNS FROM t1, Field);" | $MYSQL_TEST 2>&1
+#
+# 6. Somehow "wrong" value of parameters
+# 6.1 row parameter
+# 6.1.1 non sense number 0
+let $value= initialized;
+let $value= query_get_value(SHOW COLUMNS FROM t1, Field, 0);
+--echo value= $value
+# 6.1.2 after the last row
+let $value= initialized;
+let $value= query_get_value(SHOW COLUMNS FROM t1, Field, 10);
+--echo value= $value
+# 6.1.3 invalid row number
+--error 1
+--exec echo "let \$value= query_get_value(SHOW COLUMNS FROM t1, Field, notnumber);" | $MYSQL_TEST 2>&1
+# 6.2 column name parameter, name of not existing column
+--error 1
+--exec echo "let \$value= query_get_value(SHOW COLUMNS FROM t1, column_not_exists, 1);" | $MYSQL_TEST 2>&1
+# 6.3. statement which never gives a result set
+--error 1
+--exec echo "let \$value= query_get_value(SET @A = 1, Field, 1);" | $MYSQL_TEST 2>&1
+# 6.4. statement contains a ","
+#      Note: There is no need to improve this, because we need query_get_value
+#            for SHOW commands only.
+--error 1
+--exec echo "let \$value= query_get_value(SELECT 1 AS "A", 1 AS "B", 1);" | $MYSQL_TEST 2>&1
+#
+# 7. empty result set
+let $value= initialized;
+let $value= query_get_value(SELECT a FROM t1, a, 1);
+--echo value= $value
+#
+# 9. failing statement
+--error 1
+--exec echo "let \$value= query_get_value(SHOW COLNS FROM t1, Field, 1);" | $MYSQL_TEST 2>&1
+#
+# 10. Artificial example how to process a complete SHOW result set:
+let $show_statement= SHOW COLUMNS FROM t1;
+let $rowno= 1;
+let $run=1;
+let $count= 0;
+--echo
+--echo Field Type Null Key Default Extra
+while ($run)
+{
+   let $Field=   query_get_value($show_statement, Field,   $rowno);
+   if (`SELECT '$Field' = 'No such row'`)
+   {
+      let $run= 0;
+   }
+   if (`SELECT '$Field' <> 'No such row'`)
+   {
+      let $Type=    query_get_value($show_statement, Type,    $rowno);
+      let $Null=    query_get_value($show_statement, Null,    $rowno);
+      if (`SELECT '$Null' = 'YES'`)
+      {
+         inc $count;
+      }
+      let $Key=     query_get_value($show_statement, Key,     $rowno);
+      let $Default= query_get_value($show_statement, Default, $rowno);
+      let $Extra=   query_get_value($show_statement, Extra,   $rowno);
+      --echo $Field $Type $Null ->$Key<- $Default $Extra
+      inc $rowno;
+   }
+}
+--echo
+--echo Number of columns with Default NULL: $count
+--echo
+eval $show_statement;
+
+drop table t1;
+
 --echo End of tests
+