Commit 9b8f86f8 authored by Sergei Petrunia's avatar Sergei Petrunia

Better comments

parent 47c26d5a
......@@ -19084,7 +19084,15 @@ end_send(JOIN *join, JOIN_TAB *join_tab __attribute__((unused)),
}
/* ARGSUSED */
/*
@brief
Perform a GROUP BY operation over a stream of rows ordered by their group. The
result is sent into join->result.
@detail
Also applies HAVING, etc.
*/
enum_nested_loop_state
end_send_group(JOIN *join, JOIN_TAB *join_tab __attribute__((unused)),
bool end_of_records)
......@@ -19260,8 +19268,17 @@ end_write(JOIN *join, JOIN_TAB *join_tab __attribute__((unused)),
DBUG_RETURN(NESTED_LOOP_OK);
}
/* ARGSUSED */
/** Group by searching after group record and updating it if possible. */
/*
@brief
Perform a GROUP BY operation over rows coming in arbitrary order.
This is done by looking up the group in a temp.table and updating group
values.
@detail
Also applies HAVING, etc.
*/
static enum_nested_loop_state
end_update(JOIN *join, JOIN_TAB *join_tab __attribute__((unused)),
......@@ -19391,7 +19408,17 @@ end_unique_update(JOIN *join, JOIN_TAB *join_tab __attribute__((unused)),
}
/* ARGSUSED */
/*
@brief
Perform a GROUP BY operation over a stream of rows ordered by their group.
Write the result into a temporary table.
@detail
Also applies HAVING, etc.
The rows are written into temptable so e.g. filesort can read them.
*/
enum_nested_loop_state
end_write_group(JOIN *join, JOIN_TAB *join_tab __attribute__((unused)),
bool end_of_records)
......
......@@ -1039,7 +1039,20 @@ class JOIN :public Sql_alloc
table_map outer_join;
/* Bitmap of tables used in the select list items */
table_map select_list_used_tables;
ha_rows send_records,found_records,examined_rows,row_limit, select_limit;
ha_rows send_records,found_records,examined_rows;
/*
LIMIT for the JOIN operation. When not using aggregation or DISITNCT, this
is the same as select's LIMIT clause specifies.
Note that this doesn't take sql_calc_found_rows into account.
*/
ha_rows row_limit;
/*
How many output rows should be produced after GROUP BY.
(if sql_calc_found_rows is used, LIMIT is ignored)
*/
ha_rows select_limit;
/**
Used to fetch no more than given amount of rows per one
fetch operation of server side cursor.
......@@ -1048,8 +1061,10 @@ class JOIN :public Sql_alloc
- fetch_limit= HA_POS_ERROR if there is no cursor.
- when we open a cursor, we set fetch_limit to 0,
- on each fetch iteration we add num_rows to fetch to fetch_limit
NOTE: currently always HA_POS_ERROR.
*/
ha_rows fetch_limit;
/* Finally picked QEP. This is result of join optimization */
POSITION *best_positions;
......
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