Bug#46923: select count(*) from partitioned table fails with

ONLY_FULL_GROUP_BY

Problem was that during checking and preparation of the
partitioining function as a side effect in fix_fields
the full_group_by_flag was changed.

Solution was to set it back to its original value after
calling fix_fields.

Updated patch, to also exclude allow_sum_func from being
affected of fix_fields, as requested by reviewer.

mysql-test/r/partition.result:
  Bug#46923: select count(*) from partitioned table fails with
  ONLY_FULL_GROUP_BY
  
  Updated result file
mysql-test/t/partition.test:
  Bug#46923: select count(*) from partitioned table fails with
  ONLY_FULL_GROUP_BY
  
  Extended test case to cover this bug
sql/sql_partition.cc:
  Bug#46923: select count(*) from partitioned table fails with
  ONLY_FULL_GROUP_BY
  
  Resetting full_group_by_flag and allow_sum_func
  back to their original values,
  not conflicting with the sql_mode 'ONLY_FULL_GROUP_BY'

mysql-test/r/partition.result

@@ -2030,10 +2030,15 @@ DROP TABLE t1;
 #
 # Bug #45807: crash accessing partitioned table and sql_mode 
 #   contains ONLY_FULL_GROUP_BY
+# Bug#46923: select count(*) from partitioned table fails with
+# ONLY_FULL_GROUP_BY
 #
 SET SESSION SQL_MODE='ONLY_FULL_GROUP_BY';
 CREATE TABLE t1(id INT,KEY(id)) ENGINE=MYISAM 
 PARTITION BY HASH(id) PARTITIONS 2;
+SELECT COUNT(*) FROM t1;
+COUNT(*)
+0
 DROP TABLE t1;
 SET SESSION SQL_MODE=DEFAULT;
 #

mysql-test/t/partition.test

@@ -2018,11 +2018,14 @@ DROP TABLE t1;
 --echo #
 --echo # Bug #45807: crash accessing partitioned table and sql_mode 
 --echo #   contains ONLY_FULL_GROUP_BY
+--echo # Bug#46923: select count(*) from partitioned table fails with
+--echo # ONLY_FULL_GROUP_BY
 --echo #
 
 SET SESSION SQL_MODE='ONLY_FULL_GROUP_BY';
 CREATE TABLE t1(id INT,KEY(id)) ENGINE=MYISAM 
   PARTITION BY HASH(id) PARTITIONS 2;
+SELECT COUNT(*) FROM t1;
 DROP TABLE t1;
 SET SESSION SQL_MODE=DEFAULT;
 

sql/sql_partition.cc

@@ -905,6 +905,8 @@ bool fix_fields_part_func(THD *thd, Item* func_expr, TABLE *table,
   char* db_name;
   char db_name_string[FN_REFLEN];
   bool save_use_only_table_context;
+  uint8 saved_full_group_by_flag;
+  nesting_map saved_allow_sum_func;
   DBUG_ENTER("fix_fields_part_func");
 
   if (part_info->fixed)
@@ -974,9 +976,19 @@ bool fix_fields_part_func(THD *thd, Item* func_expr, TABLE *table,
   save_use_only_table_context= thd->lex->use_only_table_context;
   thd->lex->use_only_table_context= TRUE;
   thd->lex->current_select->cur_pos_in_select_list= UNDEF_POS;
+  saved_full_group_by_flag= thd->lex->current_select->full_group_by_flag;
+  saved_allow_sum_func= thd->lex->allow_sum_func;
+  thd->lex->allow_sum_func= 0;
   
   error= func_expr->fix_fields(thd, (Item**)&func_expr);
 
+  /*
+    Restore full_group_by_flag and allow_sum_func,
+    fix_fields should not affect mysql_select later, see Bug#46923.
+  */
+  thd->lex->current_select->full_group_by_flag= saved_full_group_by_flag;
+  thd->lex->allow_sum_func= saved_allow_sum_func;
+
   thd->lex->use_only_table_context= save_use_only_table_context;
 
   context->table_list= save_table_list;