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Port of cursors to be pushed into 5.0 tree:

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- client side part is simple and may be considered stable
- server side part now just joggles with THD state to save execution
  state and has no additional locking wisdom.
  Lot's of it are to be rewritten.
This commit is contained in:
konstantin@mysql.com
2004-08-03 03:32:21 -07:00
parent 7e6bade23b
commit d3e520ce7e
31 changed files with 1091 additions and 150 deletions
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57
sql/sql_select.h
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@ -81,6 +81,10 @@ enum join_type { JT_UNKNOWN,JT_SYSTEM,JT_CONST,JT_EQ_REF,JT_REF,JT_MAYBE_REF,
class JOIN;
typedef int (*Next_select_func)(JOIN *,struct st_join_table *,bool);
typedef int (*Read_record_func)(struct st_join_table *tab);
typedef struct st_join_table {
TABLE *table;
KEYUSE *keyuse; /* pointer to first used key */
@ -95,8 +99,8 @@ typedef struct st_join_table {
st_join_table *first_upper; /* first inner table for embedding outer join */
st_join_table *first_unmatched; /* used for optimization purposes only */
const char *info;
int (*read_first_record)(struct st_join_table *tab);
int (*next_select)(JOIN *,struct st_join_table *,bool);
Read_record_func read_first_record;
Next_select_func next_select;
READ_RECORD read_record;
double worst_seeks;
key_map const_keys; /* Keys with constant part */
@ -149,6 +153,16 @@ class JOIN :public Sql_alloc
bool do_send_rows;
table_map const_table_map,found_const_table_map,outer_join;
ha_rows send_records,found_records,examined_rows,row_limit, select_limit;
/*
Used to fetch no more than given amount of rows per one
fetch operation of server side cursor.
The value is checked in end_send and end_send_group in fashion, similar
to offset_limit_cnt:
- 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
*/
ha_rows fetch_limit;
POSITION positions[MAX_TABLES+1],best_positions[MAX_TABLES+1];
double best_read;
List<Item> *fields;
@ -239,6 +253,7 @@ class JOIN :public Sql_alloc
do_send_rows= 1;
send_records= 0;
found_records= 0;
fetch_limit= HA_POS_ERROR;
examined_rows= 0;
exec_tmp_table1= 0;
exec_tmp_table2= 0;
@ -319,6 +334,44 @@ class JOIN :public Sql_alloc
};
/*
Server-side cursor (now stands only for basic read-only cursor)
See class implementation in sql_select.cc
*/
class Cursor: public Sql_alloc, public Item_arena
{
JOIN *join;
SELECT_LEX_UNIT *unit;
TABLE *open_tables;
MYSQL_LOCK *lock;
TABLE *derived_tables;
/* List of items created during execution */
ulong query_id;
public:
select_send result;
/* Temporary implementation as now we replace THD state by value */
/* Save THD state into cursor */
void init_from_thd(THD *thd);
/* Restore THD from cursor to continue cursor execution */
void init_thd(THD *thd);
/* bzero cursor state in THD */
void reset_thd(THD *thd);
int open(JOIN *join);
int fetch(ulong num_rows);
void reset() { join= 0; }
bool is_open() const { return join != 0; }
void close();
void set_unit(SELECT_LEX_UNIT *unit_arg) { unit= unit_arg; }
Cursor() :join(0), unit(0) {}
~Cursor();
};
typedef struct st_select_check {
uint const_ref,reg_ref;
} SELECT_CHECK;