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Post WL#2126 fixes:

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* remove get_next_init and move its functionality to QUICK_RANGE_SELECT::reset()
 * added more comments
 * added empty FT_SELECT::reset()
This commit is contained in:
sergefp@mysql.com
2004-12-29 16:07:27 +03:00
parent 9c12543e18
commit fb0845f848
3 changed files with 61 additions and 85 deletions
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73
sql/opt_range.h
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@ -59,6 +59,44 @@ class QUICK_RANGE :public Sql_alloc {
/*
Quick select interface.
This class is a parent for all QUICK_*_SELECT and FT_SELECT classes.
The usage scenario is as follows:
1. Create quick select
quick= new QUICK_XXX_SELECT(...);
2. Perform lightweight initialization. This can be done in 2 ways:
2.a: Regular initialization
if (quick->init())
{
//the only valid action after failed init() call is delete
delete quick;
}
2.b: Special initialization for quick selects merged by QUICK_ROR_*_SELECT
if (quick->init_ror_merged_scan())
delete quick;
3. Perform zero, one, or more scans.
while (...)
{
// initialize quick select for scan. This may allocate
// buffers and/or prefetch rows.
if (quick->reset())
{
//the only valid action after failed reset() call is delete
delete quick;
//abort query
}
// perform the scan
do
{
res= quick->get_next();
} while (res && ...)
}
4. Delete the select:
delete quick;
*/
class QUICK_SELECT_I
@ -117,27 +155,16 @@ public:
reset() should be called when it is certain that row retrieval will be
necessary. This call may do heavyweight initialization like buffering first
N records etc. If reset() call fails get_next() must not be called.
Note that reset() may be called several times if this quick select
executes in a subselect.
Note that reset() may be called several times if
* the quick select is executed in a subselect
* a JOIN buffer is used
RETURN
0 OK
other Error code
*/
virtual int reset(void) = 0;
/*
Initialize get_next() for row retrieval.
SYNOPSIS
get_next_init()
get_next_init() must be called before the first get_next().
If get_next_init() call fails get_next() must not be called.
RETURN
0 OK
other Error code
*/
virtual int get_next_init() { return false; }
virtual int get_next() = 0; /* get next record to retrieve */
/* Range end should be called when we have looped over the whole index */
@ -284,18 +311,7 @@ public:
~QUICK_RANGE_SELECT();
int init();
int reset(void)
{
next=0;
range= NULL;
cur_range= (QUICK_RANGE**) ranges.buffer;
/*
Note: in opt_range.cc there are places where it is assumed that this
function always succeeds
*/
return 0;
}
int get_next_init(void);
int reset(void);
int get_next();
void range_end();
int get_next_prefix(uint prefix_length, byte *cur_prefix);
@ -310,6 +326,8 @@ public:
#ifndef DBUG_OFF
void dbug_dump(int indent, bool verbose);
#endif
private:
/* Used only by QUICK_SELECT_DESC */
QUICK_RANGE_SELECT(const QUICK_RANGE_SELECT& org) : QUICK_SELECT_I()
{
bcopy(&org, this, sizeof(*this));
@ -685,6 +703,7 @@ public:
QUICK_RANGE_SELECT (thd, table, key, 1) { init(); }
~FT_SELECT() { file->ft_end(); }
int init() { return error=file->ft_init(); }
int reset() { return 0; }
int get_next() { return error=file->ft_read(record); }
int get_type() { return QS_TYPE_FULLTEXT; }
};