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Cleanup of sql_join_cache code (no logic changes)

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- Remove virtual from get_min_join_buffer_size() and
  get_max_join_buffer_size().
- Avoid some calls to get_min_buffer_size()
- Simply cache usage in get_..._join_buffer_size()
- Simplify get_max_join_buffer_size() when using optimize_buff_size
- Reindented some long comments

Reviewer: Sergei Petrunia <sergey@mariadb.com>
This commit is contained in:
Monty
2023-05-04 13:06:39 +03:00
parent 5fd46be5a7
commit e74390d94f
2 changed files with 85 additions and 82 deletions
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162
sql/sql_join_cache.cc
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@ -694,16 +694,22 @@ void JOIN_CACHE::set_constants()
(prev_cache ? prev_cache->get_size_of_rec_offset() : 0) +
length + fields*sizeof(uint);
pack_length_with_blob_ptrs= pack_length + blobs*sizeof(uchar *);
min_buff_size= 0;
min_records= 1;
min_buff_size= get_min_join_buffer_size();
buff_size= (size_t)MY_MAX(join->thd->variables.join_buff_size,
get_min_join_buffer_size());
min_buff_size);
size_of_rec_ofs= offset_size(buff_size);
size_of_rec_len= blobs ? size_of_rec_ofs : offset_size(len);
size_of_fld_ofs= size_of_rec_len;
base_prefix_length= (with_length ? size_of_rec_len : 0) +
(prev_cache ? prev_cache->get_size_of_rec_offset() : 0);
/*
/*
Call ge_min_join_buffer_size() again as the size may have got smaller
if size_of_rec_ofs or some other variable changed since last call.
*/
min_buff_size= 0;
min_buff_size= get_min_join_buffer_size();
/*
The size of the offsets for referenced fields will be added later.
The values of 'pack_length' and 'pack_length_with_blob_ptrs' are adjusted
every time when the first reference to the referenced field is registered.
@ -767,30 +773,29 @@ uint JOIN_CACHE::get_record_max_affix_length()
size_t JOIN_CACHE::get_min_join_buffer_size()
{
if (!min_buff_size)
if (min_buff_size)
return min_buff_size; // use cached value
size_t len= 0, len_last= 0, len_addon, min_sz, add_sz= 0;
for (JOIN_TAB *tab= start_tab; tab != join_tab;
tab= next_linear_tab(join, tab, WITHOUT_BUSH_ROOTS))
{
size_t len= 0;
size_t len_last= 0;
for (JOIN_TAB *tab= start_tab; tab != join_tab;
tab= next_linear_tab(join, tab, WITHOUT_BUSH_ROOTS))
{
len+= tab->get_max_used_fieldlength();
len_last+= tab->get_used_fieldlength();
}
size_t len_addon= get_record_max_affix_length() +
get_max_key_addon_space_per_record();
len+= len_addon;
len_last+= len_addon;
size_t min_sz= len*(min_records-1) + len_last;
min_sz+= pack_length_with_blob_ptrs;
size_t add_sz= 0;
for (uint i=0; i < min_records; i++)
add_sz+= join_tab_scan->aux_buffer_incr(i+1);
avg_aux_buffer_incr= add_sz/min_records;
min_sz+= add_sz;
set_if_bigger(min_sz, 1);
min_buff_size= min_sz;
len+= tab->get_max_used_fieldlength();
len_last+= tab->get_used_fieldlength();
}
len_addon= (get_record_max_affix_length() +
get_max_key_addon_space_per_record());
len+= len_addon;
len_last+= len_addon;
min_sz= len*(min_records-1) + len_last;
min_sz+= pack_length_with_blob_ptrs;
for (uint i=0; i < min_records; i++)
add_sz+= join_tab_scan->aux_buffer_incr(i+1);
avg_aux_buffer_incr= add_sz/min_records;
min_sz+= add_sz;
set_if_bigger(min_sz, 1);
min_buff_size= min_sz;
return min_buff_size;
}
@ -822,48 +827,48 @@ size_t JOIN_CACHE::get_min_join_buffer_size()
The maximum possible size of the join buffer of this cache
*/
size_t JOIN_CACHE::get_max_join_buffer_size(bool optimize_buff_size)
size_t JOIN_CACHE::get_max_join_buffer_size(bool optimize_buff_size,
size_t min_sz)
{
if (!max_buff_size)
if (max_buff_size)
return max_buff_size; // use cached value
size_t limit_sz= (size_t) join->thd->variables.join_buff_size;
if (!optimize_buff_size)
return max_buff_size= limit_sz;
size_t max_sz;
size_t len= 0;
double max_records, partial_join_cardinality=
(join_tab-1)->get_partial_join_cardinality();
/* Expected join buffer space used for one record */
size_t space_per_record;
for (JOIN_TAB *tab= start_tab; tab != join_tab;
tab= next_linear_tab(join, tab, WITHOUT_BUSH_ROOTS))
{
size_t max_sz;
size_t min_sz= get_min_join_buffer_size();
size_t len= 0;
double max_records, partial_join_cardinality=
(join_tab-1)->get_partial_join_cardinality();
size_t limit_sz= (size_t) join->thd->variables.join_buff_size;
/* Expected join buffer space used for one record */
size_t space_per_record;
for (JOIN_TAB *tab= start_tab; tab != join_tab;
tab= next_linear_tab(join, tab, WITHOUT_BUSH_ROOTS))
{
len+= tab->get_used_fieldlength();
}
len+= get_record_max_affix_length();
avg_record_length= len;
len+= get_max_key_addon_space_per_record() + avg_aux_buffer_incr;
space_per_record= len;
/* Note that space_per_record can be 0 if no table fields where used */
max_records= (double) (limit_sz / MY_MAX(space_per_record, 1));
set_if_smaller(max_records, partial_join_cardinality);
set_if_bigger(max_records, 10.0);
if (!optimize_buff_size)
max_sz= limit_sz;
else
{
if ((size_t) (limit_sz / max_records) > space_per_record)
max_sz= space_per_record * (size_t) max_records;
else
max_sz= limit_sz;
max_sz+= pack_length_with_blob_ptrs;
set_if_smaller(max_sz, limit_sz);
}
set_if_bigger(max_sz, min_sz);
max_buff_size= max_sz;
len+= tab->get_used_fieldlength();
}
len+= get_record_max_affix_length();
avg_record_length= len;
len+= get_max_key_addon_space_per_record() + avg_aux_buffer_incr;
space_per_record= len;
/* Note that space_per_record can be 0 if no table fields where used */
max_records= (double) (limit_sz / MY_MAX(space_per_record, 1));
set_if_smaller(max_records, partial_join_cardinality);
set_if_bigger(max_records, 10.0);
if ((size_t) (limit_sz / max_records) > space_per_record)
max_sz= space_per_record * (size_t) max_records;
else
max_sz= limit_sz;
max_sz+= pack_length_with_blob_ptrs;
set_if_smaller(max_sz, limit_sz);
set_if_bigger(max_sz, min_sz);
max_buff_size= max_sz;
return max_buff_size;
}
@ -906,11 +911,7 @@ int JOIN_CACHE::alloc_buffer()
bool optimize_buff_size=
optimizer_flag(join->thd, OPTIMIZER_SWITCH_OPTIMIZE_JOIN_BUFFER_SIZE);
buff= NULL;
min_buff_size= 0;
max_buff_size= 0;
min_records= 1;
min_buff_size= get_min_join_buffer_size();
buff_size= get_max_join_buffer_size(optimize_buff_size);
buff_size= get_max_join_buffer_size(optimize_buff_size, min_buff_size);
for (tab= start_tab; tab!= join_tab;
tab= next_linear_tab(join, tab, WITHOUT_BUSH_ROOTS))
@ -1093,18 +1094,19 @@ int JOIN_CACHE::init(bool for_explain)
/*
Check the possibility to read the access keys directly from the join buffer
Check the possibility to read the access keys directly from the join buffer
SYNOPSIS
check_emb_key_usage()
DESCRIPTION
The function checks some conditions at which the key values can be read
directly from the join buffer. This is possible when the key values can be
composed by concatenation of the record fields stored in the join buffer.
Sometimes when the access key is multi-component the function has to re-order
the fields written into the join buffer to make keys embedded. If key
values for the key access are detected as embedded then 'use_emb_key'
is set to TRUE.
The function checks some conditions at which the key values can be
read directly from the join buffer. This is possible when the key
values can be composed by concatenation of the record fields
stored in the join buffer. Sometimes when the access key is
multi-component the function has to re-order the fields written
into the join buffer to make keys embedded. If key values for the
key access are detected as embedded then 'use_emb_key' is set to
TRUE.
EXAMPLE
Let table t2 has an index defined on the columns a,b . Let's assume also
@ -1257,7 +1259,7 @@ bool JOIN_CACHE::check_emb_key_usage()
trailing spaces
- significant part of fixed length fields that can have trailing spaces
with the prepanded length
- data of non-blob variable length fields with the prepanded data length
- data of non-blob variable length fields with the prepanded data length
- blob data from blob fields with the prepanded data length
(5) record offset values for the data fields that are referred to from
other caches
@ -1328,7 +1330,7 @@ uint JOIN_CACHE::write_record_data(uchar * link, bool *is_full)
Check whether we won't be able to add any new record into the cache after
this one because the cache will be full. Set last_record to TRUE if it's so.
The assume that the cache will be full after the record has been written
into it if either the remaining space of the cache is not big enough for the
into it if either the remaining space of the cache is not big enough for the
record's blob values or if there is a chance that not all non-blob fields
of the next record can be placed there.
This function is called only in the case when there is enough space left in
@ -1350,7 +1352,7 @@ uint JOIN_CACHE::write_record_data(uchar * link, bool *is_full)
/*
Put a reference to the fields of the record that are stored in the previous
cache if there is any. This reference is passed by the 'link' parameter.
cache if there is any. This reference is passed by the 'link' parameter.
*/
if (prev_cache)
{