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DS-MRR improvements: more code cleanup

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- better comments
- rename variables to better reflect their meaning
This commit is contained in:
Sergey Petrunya
2010-09-20 13:02:17 +04:00
parent 18a348503a
commit 189555f39a
2 changed files with 165 additions and 123 deletions
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213
sql/multi_range_read.h
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@ -73,7 +73,9 @@
start | | end
| |
usused space user data
For reverse buffer, start/end have the same meaning, but reading and
writing is done from end to start.
*/
class SimpleBuffer
@ -134,7 +136,6 @@ public:
/* Read-mode functions */
bool is_empty() { return used_size() == 0; }
void reset_for_reading();
void setup_reading(uchar **data1, size_t len1,
uchar **data2, size_t len2);
bool read();
@ -209,23 +210,31 @@ public:
*/
class PeekIterator
{
SimpleBuffer *buf; /* The buffer we're iterating over*/
/*
if sb->direction==1 : pointer to what to return next
if sb->direction==-1: pointer to the end of what is to be returned next
if buf->direction==FORWARD : pointer to what to return next
if buf->direction==BACKWARD : pointer to the end of what is to be
returned next
*/
uchar *pos;
SimpleBuffer *sb;
public:
void init(SimpleBuffer *sb_arg)
/*
Initialize the iterator. After intiialization, the first read_next() call
will read what buf_arg->read() would read.
*/
void init(SimpleBuffer *buf_arg)
{
sb= sb_arg;
pos= sb->read_pos;
buf= buf_arg;
pos= buf->read_pos;
}
/*
If the buffer stores tuples, this call will return pointer to the first
component.
Read the next value. The calling convention is the same as buf->read()
has.
RETURN
FALSE - Ok
TRUE - EOF, reached the end of the buffer
*/
bool read_next()
{
@ -234,11 +243,11 @@ public:
have written the second component first).
*/
uchar *res;
if ((res= get_next(sb->read_size1)))
if ((res= get_next(buf->read_size1)))
{
*(sb->read_ptr1)= res;
if (sb->read_ptr2)
*sb->read_ptr2= get_next(sb->read_size2);
*(buf->read_ptr1)= res;
if (buf->read_ptr2)
*buf->read_ptr2= get_next(buf->read_size2);
return FALSE;
}
return TRUE; /* EOF */
@ -247,9 +256,9 @@ public:
/* Return pointer to next chunk of nbytes bytes and avance over it */
uchar *get_next(size_t nbytes)
{
if (sb->direction == 1)
if (buf->direction == 1)
{
if (pos + nbytes > sb->write_pos)
if (pos + nbytes > buf->write_pos)
return NULL;
uchar *res= pos;
pos += nbytes;
@ -257,7 +266,7 @@ public:
}
else
{
if (pos - nbytes < sb->write_pos)
if (pos - nbytes < buf->write_pos)
return NULL;
pos -= nbytes;
return pos;
@ -288,6 +297,8 @@ private:
S2. Sort Keys
S3. Sort Rowids
psergey-TODO.
S1 is used for cases which DS-MRR is unable to handle for some reason.
S2 is the actual DS-MRR. The basic algorithm is as follows:
@ -339,75 +350,78 @@ public:
uint *flags, COST_VECT *cost);
private:
/*
The "owner" handler object (the one that calls dsmrr_XXX functions.
It is used to retrieve full table rows by calling rnd_pos().
The "owner" handler object (the one that is expected to "own" this object
and call its functions).
*/
handler *h;
TABLE *table; /* Always equal to h->table */
/*
Secondary handler object, if needed (we need it when we need to both scan
the index and return rows).
Secondary handler object. (created when needed, we need it when we need
to run both index scan and rnd_pos() at the same time)
*/
handler *h2;
/* Full buffer that we're using (the buffer is obtained from SQL layer) */
/** Properties of current MRR scan **/
uint keyno; /* index we're running the scan on */
bool use_default_impl; /* TRUE <=> shortcut all calls to default MRR impl */
/* TRUE <=> need range association, buffers hold {rowid, range_id} pairs */
bool is_mrr_assoc;
/* TRUE <=> sort the keys before making index lookups */
bool do_sort_keys;
/* TRUE <=> sort rowids and use rnd_pos() to get and return full records */
bool do_rndpos_scan;
/*
(if do_sort_keys==TRUE) don't copy key values, use pointers to them
instead.
*/
bool use_key_pointers;
/* The whole buffer space that we're using */
uchar *full_buf;
uchar *full_buf_end;
/* Valid when using both rowid and key buffer: the original bound between them */
uchar *rowid_buffer_end;
/* Buffer to store rowids, or (rowid, range_id) pairs */
SimpleBuffer rowid_buffer;
/* Reads from rowid buffer go to here: */
uchar *rowid;
uchar *rowids_range_id;
/*
not-NULL: we're traversing a group of (rowid, range_id) pairs with
identical rowid values, and this is the pointer to the last one.
NULL: we're not in the group of indentical rowids.
*/
uchar *last_identical_rowid;
/* Identical keys */
bool in_identical_keys_range;
uchar *last_identical_key_ptr;
SimpleBuffer::PeekIterator identical_key_it;
SimpleBuffer key_buffer;
uint keyno;
/* Execution control */
bool do_sort_keys;
bool use_key_pointers;
bool do_rowid_fetch;
bool dsmrr_eof; /* TRUE <=> We have reached EOF when reading index tuples */
/*
TRUE <=> key buffer is exhausted (we need this because we may have a situation
where we've read everything from the key buffer but haven't finished with
scanning the last range)
When using both rowid and key buffers: the bound between key and rowid
parts of the buffer. This is the "original" value, actual memory ranges
used by key and rowid parts may be different because of dynamic space
reallocation between them.
*/
uchar *rowid_buffer_end;
/** Index scaning and key buffer-related members **/
/* TRUE <=> We can get at most one index tuple for a lookup key */
bool index_ranges_unique;
/* TRUE<=> we're in a middle of enumerating records for a key range */
bool in_index_range;
/* Buffer to store (key, range_id) pairs */
SimpleBuffer key_buffer;
/* key_buffer.read() reads */
uchar *cur_index_tuple;
/* if in_index_range==TRUE: range_id of the range we're enumerating */
char *cur_range_info;
/*
TRUE <=> we've got index tuples/rowids for all keys (need this flag because
we may have a situation where we've read everything from the key buffer but
haven't finished with getting index tuples for the last key)
*/
bool key_eof;
/* TRUE <=> need range association, buffer holds {rowid, range_id} pairs */
bool is_mrr_assoc;
bool use_default_impl; /* TRUE <=> shortcut all calls to default MRR impl */
bool doing_cpk_scan; /* TRUE <=> DS-MRR/CPK variant is used */
/* Initially FALSE, becomes TRUE when we've set key_tuple_xxx members */
bool know_key_tuple_params;
/* Length of lookup tuple being used, in bytes */
uint key_tuple_length;
key_part_map key_tuple_map;
uint key_tuple_length; /* Length of index lookup tuple, in bytes */
key_part_map key_tuple_map; /* keyparts used in index lookup tuples */
/*
This is
= key_tuple_length if we copy keys to buffer
@ -418,23 +432,52 @@ private:
/* = key_size_in_keybuf [ + sizeof(range_assoc_info) ] */
uint key_buff_elem_size;
/*
TRUE <=> we're doing key-ordered index scan and right now several
subsequent key values are the same as the one we've already retrieved and
returned index tuple for.
*/
bool in_identical_keys_range;
/* range_id of the first of the identical keys */
char *first_identical_range_info;
/* Pointer to the last of the identical key values */
uchar *last_identical_key_ptr;
/*
key_buffer iterator for walking the identical key range (we need to
enumerate the set of (identical_key, range_id) pairs multiple times,
and do that by walking from current buffer read position until we get
last_identical_key_ptr.
*/
SimpleBuffer::PeekIterator identical_key_it;
/** rnd_pos() scan and rowid buffer-related members **/
/*
Buffer to store (rowid, range_id) pairs, or just rowids if
is_mrr_assoc==FALSE
*/
SimpleBuffer rowid_buffer;
/* rowid_buffer.read() will set the following: */
uchar *rowid;
uchar *rowids_range_id;
/*
not-NULL: we're traversing a group of (rowid, range_id) pairs with
identical rowid values, and this is the pointer to the last one.
NULL: we're not in the group of indentical rowids.
*/
uchar *last_identical_rowid;
bool dsmrr_eof; /* TRUE <=> We have reached EOF when reading index tuples */
/* = h->ref_length [ + sizeof(range_assoc_info) ] */
uint rowid_buff_elem_size;
/*
TRUE <=> We're scanning on a full primary key (and not on prefix), and so
can get max. one match for each key
*/
bool index_ranges_unique;
/* TRUE<=> we're in a middle of enumerating records from a range */
bool in_index_range;
uchar *cur_index_tuple;
/* if in_index_range==TRUE: range_id of the range we're enumerating */
char *cur_range_info;
char *first_identical_range_info;
bool choose_mrr_impl(uint keyno, ha_rows rows, uint *flags, uint *bufsz,
COST_VECT *cost);
bool get_disk_sweep_mrr_cost(uint keynr, ha_rows rows, uint flags,
@ -446,8 +489,10 @@ private:
int dsmrr_next_from_index(char **range_info);
void setup_buffer_sizes(key_range *sample_key);
void reallocate_buffer_space();
static range_seq_t key_buf_seq_init(void *init_param, uint n_ranges, uint flags);
static uint key_buf_seq_next(range_seq_t rseq, KEY_MULTI_RANGE *range);
};