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Added comments to all methods. Added explanation for a sequential read through a storage engine.

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This commit is contained in:
brian@brian-akers-computer.local
2004-05-11 15:59:20 -07:00
parent c745ae9503
commit 346ae5fe33
2 changed files with 401 additions and 9 deletions
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40
sql/examples/ha_example.h
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@@ -14,6 +14,17 @@
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */
/*
Please read ha_exmple.cc before reading this file.
Please keep in mind that the example storage engine implements all methods
that are required to be implemented. handler.h has a full list of methods
that you can implement.
*/
/*
EXAMPLE_SHARE is a structure that will be shared amoung all open handlers
The example implements the minimum of what you will probably need.
*/
typedef struct st_example_share {
char *table_name;
uint table_name_length,use_count;
@@ -21,6 +32,9 @@ typedef struct st_example_share {
THR_LOCK lock;
} EXAMPLE_SHARE;
/*
Class definition for the storage engine
*/
class ha_example: public handler
{
THR_LOCK_DATA lock; /* MySQL lock */
@@ -33,17 +47,34 @@ public:
~ha_example()
{
}
const char *table_type() const { return "EXAMPLE"; }
/* The name that will be used for display purposes */
const char *table_type() const { return "EXAMPLE"; }
/* The name of the index type that will be used for display */
const char *index_type(uint inx) { return "NONE"; }
const char **bas_ext() const;
/*
This is a list of flags that says what the storage engine
implements. The current table flags are documented in
table_flags.
*/
ulong table_flags() const
{
return 0;
}
/*
This is a list of flags that says how the storage engine
implements indexes. The current index flags are documented in
handler.h. If you do not implement indexes, just return zero
here.
*/
ulong index_flags(uint inx) const
{
return 0;
}
/*
unireg.cc will call the following to make sure that the storage engine can
handle the data it is about to send.
*/
uint max_record_length() const { return HA_MAX_REC_LENGTH; }
uint max_keys() const { return 0; }
uint max_key_parts() const { return 0; }
@@ -52,10 +83,15 @@ public:
Called in test_quick_select to determine if indexes should be used.
*/
virtual double scan_time() { return (double) (records+deleted) / 20.0+10; }
/* The next method will never be called */
/*
The next method will never be called if you do not implement indexes.
*/
virtual double read_time(ha_rows rows) { return (double) rows / 20.0+1; }
virtual bool fast_key_read() { return 1;}
/*
Everything below are methods that we implment in ha_example.cc.
*/
int open(const char *name, int mode, uint test_if_locked);
int close(void);
int write_row(byte * buf);