概述
條件查詢被廣泛的使用在SQL查詢中，複雜條件是否能在執行過程中被優化，比如恒為true或者false的條件，可以合并的條件。另外，由于索引是MySQL通路資料的基本方式，已經追求更快的通路方式，SARGable這個概念已經被我們遺忘了，因為他已經成為預設必要的方法（Search ARGument ABLE）。MySQL如何組織複雜條件并計算各個Ranges所影響到的對應可以使用的索引的代價和使用索引的不同快速方式，進而選出最優的計劃，另外，MySQL分區表如何有效的進行條件剪枝？這都離不開一個結構mm tree。下面就讓我們來揭開它的真實面紗。
我們在解決客戶問題時
本文章的例子如下：
create table tmp_sel_arg(kp1 int, kp2 int, kp3 int, kp4 int);
create index ind_tmp_sel_arg on tmp_sel_arg(kp1, kp2, kp3);
select * from tmp_sel_arg where
(kp1 < 1 AND kp2=5 AND (kp3=10 OR kp3=12)) OR
(kp1=2 AND (kp3=11 OR kp3=14)) OR
(kp1=3 AND (kp3=11 OR kp3=14)); 源代碼路徑：./sql/opt_range.cc
SEL_TREE 圖結構
SEL_TREE結構的定義，記錄選擇的表上所有可選擇的索引的圖結構，針對索引的類森林數組
class SEL_TREE {
Mem_root_array keys;
Key_map keys_map; /* bitmask of non-NULL elements in keys */
enum Type { IMPOSSIBLE, ALWAYS, MAYBE, KEY, KEY_SMALLER } type;
.......
}
IMPOSSIBLE: if keys[i]->type == SEL_ROOT::Type::IMPOSSIBLE for some i, then type == SEL_TREE::IMPOSSIBLE. Rationale: if the predicate for one of the indexes is always false, then the full predicate is also always false.
ALWAYS: if either (keys[i]->is_always()) or (keys[i] == NULL) for all i, then type == SEL_TREE::ALWAYS. Rationale: the range access method will not be able to filter out any rows when there are no range predicates that can be used to filter on any index.
KEY: There are range predicates that can be used on at least one index.
KEY_SMALLER: There are range predicates that can be used on at least one index. In addition, there are predicates that cannot be directly utilized by range access on key parts in the same index. These unused predicates makes it probable that the row estimate for range access on this index is too pessimistic. SEL_ROOT 圖結構
索引Range的圖結構，針對于索引列的森林樹結構
A graph of (possible multiple) key ranges, represented as a red-black binary tree. There are three types (see the Type enum); if KEY_RANGE, we have zero or more SEL_ARGs, described in the documentation on SEL_ARG.
class SEL_ROOT {
/**
Used to indicate if the range predicate for an index is always
true/false, depends on values from other tables or can be
evaluated as is.
*/
enum class Type {
/** The range predicate for this index is always false. */
IMPOSSIBLE,
/**
There is a range predicate that refers to another table. The
range access method cannot be used on this index unless that
other table is earlier in the join sequence. The bit
representing the index is set in JOIN_TAB::needed_reg to
notify the join optimizer that there is a table dependency.
After deciding on join order, the optimizer may chose to rerun
the range optimizer for tables with such dependencies.
*/
MAYBE_KEY,
/**
There is a range condition that can be used on this index. The
range conditions for this index in stored in the SEL_ARG tree.
*/
KEY_RANGE
} type;
SEL_ARG *root; // The root node of the tree
}
SEL_ARG 圖結構
記錄了索引列的RB Tree結構，有兩種表示形式，内部link和RB tree，各個keypart通過next_key_part相連
class SEL_ARG {
......
Field *field{nullptr};
uchar *min_value, *max_value; // Pointer to range
......
SEL_ARG *left, *right; /* R-B tree children */
SEL_ARG *next, *prev; /* Links for bi-directional interval list */
SEL_ARG *parent{nullptr}; /* R-B tree parent (nullptr for root) */
/*
R-B tree of intervals covering keyparts consecutive to this
SEL_ARG. See documentation of SEL_ARG GRAPH semantics for details.
*/
SEL_ROOT *next_key_part{nullptr};
......
} Red-Black樹結構
通過下面例子來展示内部的RB樹結構如圖：
(kp1 < 1 AND kp2=5 AND (kp3=10 OR kp3=12)) OR (kp1=2 AND (kp3=11 OR kp3=14)) OR
(kp1=3 AND (kp3=11 OR kp3=14));
Where / and \ denote left and right pointers and ... denotes next_key_part pointers to the root of the R-B tree of intervals for consecutive key parts.
tree->keys[0]
0x7f59cf68a588
SEL_ROOT::Type::KEY_RANGE 0x7f59cf68aa90
use_count = 1, elements = 3 SEL_ROOT::Type::KEY_RANGE
|| --> use_count = 1, elements = 2
|| : ||
\/ : \/
0x7f59cf68ac40 : 0x7f59cf68aa10
min_item=max_item=2 BLACK : min_item=max_item=11 BLACK
+-------+ : +--------+
| kp1=2 |.............. | kp3=11 |
+-------+ +--------+
/ \ \
0x7f59cf68a508 0x7f59cf68af88 0x7f59cf68ab28
max_item=1 RED min_item=max_item=3 RED min_item=max_item=14 RED
+-------+ +-------+ +--------+
| kp1<1 | | kp1=3 | | kp3=14 |
+-------+ +-------+ +--------+
: :
...... .......
: :
SEL_ROOT::Type::KEY_RANGE SEL_ROOT::Type::KEY_RANGE
use_count = 1, elements = 1 use_count = 1, elements = 2
|| ||
\/ \/
0x7f59cf68a8f8 0x7f59cf68ad58
min_item=max_item=5 BLACK min_item=max_item=11 BLACK
+-------+ +--------+
| kp2=5 | | kp3=11 |
+-------+ +--------+
. \
...... 0x7f59cf68ae70
. min_item=max_item=14 RED
0x7f59cf68a6a8 +--------+
SEL_ROOT::Type::KEY_RANGE | kp3=14 |
use_count = 1, elements = 2 +--------+
||
\/
0x7f59cf68a628
min_item=max_item=10 BLACK
+--------+
| kp3=10 |
+--------+
\
0x7f59cf68a740
min_item=max_item=12 RED
+--------+
| kp3=12 |
+--------+
内部的雙向連結清單
SEL_ARG一組對象合成一個SEL_ROOT的圖結構，内部通過SEL_ARG::next/prev來關聯同一個索引列條件"OR"，通過next_key_part來關聯不同索引列條件的"AND"
tree->keys[0] (SEL_ROOT::Type::KEY_RANGE)
|
| $ $
| part=1 $ part=2 $ part=3
| 0x7f59cf68a508 $ 0x7f59cf68a8f8 $ 0x7f59cf68a628
| left(RED) $ root(BLACK) $ root(BLACK)
| +-------+ $ +-------+ $ +--------+
| | kp1<1 |--------$------->| kp2=5 |-------$------>| kp3=10 |
| +-------+ $ +-------+ $ +--------+
| | $ $ |
| | $ $ right(RED)
| | $ $ 0x7f59cf68a740
| | $ $ +--------+
| | $ $ | kp3=12 |
| | $ $ +--------+
| | $ $
| 0x7f59cf68ac40 $ $ 0x7f59cf68aa10
| root(BLACK) $ $ root(BLACK)
| +-------+ $ $ +--------+
\------>| kp1=2 |-------$------------------------$------>| kp3=11 |
+-------+ $ $ +--------+
| $ $ |
| $ $ right(RED)
| $ $ 0x7f59cf68ab28
| $ $ +--------+
| $ $ | kp3=14 |
| $ $ +--------+
| $ $
right(RED) $ $ root(BLACK)
0x7f59cf68af88 $ $ 0x7f59cf68ad58
+-------+ $ $ +--------+
| kp1=3 |-------$------------------------$------>| kp3=11 |
+-------+ $ $ +--------+
$ $ |
$ $ right(RED)
$ $ 0x7f59cf68ae70
$ $ +--------+
$ $ | kp3=14 |
$ $ +--------+ SEL_ARG flag辨別
SEL_ARGs flag一共有6個bit來記錄不同含義。前四個是借鑒enum key_range_flags.
flag = min_flag && max_flag
/*
The valid SEL_ARG representations are enumerated here:
bit5 bit4 bit3 bit2 bit1 bit0
NULL NULL NEAR NEAR NO NO
flag MAX MIN MAX MIN MAX MIN notation expr
0 0 0 0 0 0 0 [a, a] X == a
0 0 0 0 0 0 0 [a, b] X >= a && X <= b
4 0 0 0 1 0 0 (a, b] X > a && X <= b
8 0 0 1 0 0 0 [a, b) X >= a && X < b
C 0 0 1 1 0 0 (a, b) X > a && X < b
1 0 0 0 - 0 1 b] X <= b
2 0 0 - 0 1 0 [a, X >= a
6 0 0 - 1 1 0 (a, X > a
9 0 0 1 - 0 1 b) X < b
10 0 1 - 0 0 0 [NULL, b] X IS NULL || X <= b
18 0 1 - 0 1 0 [NULL, b) X IS NULL || X < b
30 1 1 - 0 0 0 [NULL, NULL] X IS NULL
14 0 1 0 1 0 0 (NULL, b] X <= b (nullable X)
1C 0 1 1 1 0 0 (NULL, b) X < b (nullable X)
16 - 1 - 1 1 0 (NULL, X IS NOT NULL 如何構造mm tree
get_mm_tree (mm=min_max) 函數
Range分析子產品，用于找到所有可能索引的mm tree，構造的ranges可能會比原有的條件範圍更大，比如下面簡單的兩個索引列和條件：
"WHERE fld1 > 'x' AND fld2 > 'y'" 這種場景，不論選擇fld1的索引或者fld2的索引，可能讀到的行數都比最終結果集多
static SEL_TREE *get_mm_tree(RANGE_OPT_PARAM *param, Item *cond) {
// Item And
while itemlist
new_tree = get_mm_tree
tree = tree_and(param, tree, new_tree);
// Item Or
while itemlist
new_tree = get_mm_tree
tree = tree_or(param, tree, new_tree);
} get_full_func_mm_tree 函數
需要考慮所有等值列，構造多個mm trees
WHERE t1.a=t2.a AND t2.a > 10 ==> WHERE t1.a=t2.a AND t2.a > 10 AND t1.a > 10
field->item_equal
The class Item_equal is used to represent conjunctions of equality | sql/sql_gather.cc:1824: List_iterator_fast li(cond_equal->current_level)$
predicates of the form field1 = field2, and field=const in where | sql/sql_gather.cc:1825: Item_equal *item;
conditions and on expressions. A BETWEEN predicate :
fi [NOT] BETWEEN c1 AND c2
AND j,k (f1j <=c AND f2k<=c)
IN predicates:
f IN (c1,...,cn)
c IN (c1,...,f,...,cn) --> never try to narrow the index scan
get_func_mm_tree 函數
構造mm tree的入口函數
switch(func type) {
Item_func::NE_FUNC : get_ne_mm_tree
Item_func::BETWEEN : get_mm_parts
Item_func::IN_FUNC : get_func_mm_tree_from_in_predicate
default : get_mm_parts // <, <=, =, >=, >, LIKE, IS NULL, IS NOT NULL and GIS functions.
} get_ne_mm_tree 函數
針對于 SEL_TREE for <> or NOT BETWEEN 條件構造mm tree
kp1 <> 1 => kp1 < 1 or kp1 > 1
tree_or(kp1 < 1 , kp1 > 1)
(gdb) my sel tree
$k0 (SEL_TREE *) 0x7f7cf17c0cd0 [type=SEL_TREE::KEY,keys.m_size=1]
`--$k1 (SEL_ROOT *) 0x7f7cf17c0dc8 [type=SEL_ROOT::Type::KEY_RANGE, use_count=1, elements=2]
`--$k2 (SEL_ARG *) 0x7f7cf17c0d48 [color=SEL_ARG::BLACK, is_asc=true, minflag=4 '\004', maxflag=8 '\b', part=0 '\000', selectivity=1]
| field = $k3 (Item_field *) 0x7f7cf04af268 field = test.tmp_sel_arg1.kp1
| scope = ( -infinity, $k4 (Item_int *) 0x7f7cf04ae670 value = 1 )
`--$k6 (SEL_ARG *) 0x7f7cf17c0e68 [color=SEL_ARG::RED, is_asc=true, minflag=4 '\004', maxflag=2 '\002', part=0 '\000', selectivity=1]
| field = $k7 (Item_field *) 0x7f7cf04af268 field = test.tmp_sel_arg1.kp1
| scope = ( $k8 (Item_int *) 0x7f7cf04ae670 value = 1, +infinity ) get_mm_parts 函數
通用的通過Item cond構造mm tree的方法
for (every key part) {
SEL_ROOT root = get_mm_leaf
SEL_TREE tree.root = root
} get_func_mm_tree_from_in_predicate 函數
通過IN value構造mm tree
select * from tmp_sel_arg1 where kp1 in (1, 2, 3, 4, 5) and kp2 < 4;
(gdb) my sel tree
$d0 (SEL_TREE *) 0x7f7cf17c0cd0 [type=SEL_TREE::KEY,keys.m_size=2]
|--$d1 (SEL_ROOT *) 0x7f7cf17c0dd0 [type=SEL_ROOT::Type::KEY_RANGE, use_count=1, elements=5]
| `--$d2 (SEL_ARG *) 0x7f7cf17c0e70 [color=SEL_ARG::BLACK, is_asc=true, minflag=0 '\000', maxflag=0 '\000', part=0 '\000', selectivity=1]
| | field = $d3 (Item_field *) 0x7f7cf0444938 field = test.tmp_sel_arg1.kp1
| | equal = [ $d4 (Item_int *) 0x7f7cf0d96420 value = 2 ]
| |--$d6 (SEL_ARG *) 0x7f7cf17c0d50 [color=SEL_ARG::BLACK, is_asc=true, minflag=0 '\000', maxflag=0 '\000', part=0 '\000', selectivity=1]
| | | field = $d7 (Item_field *) 0x7f7cf0444938 field = test.tmp_sel_arg1.kp1
| | | equal = [ $d8 (Item_int *) 0x7f7cf0d96320 value = 1 ]
| | `--$d12 (SEL_ROOT *) 0x7f7cf17c1370 [type=SEL_ROOT::Type::KEY_RANGE, use_count=5, elements=1]
| | `--$d13 (SEL_ARG *) 0x7f7cf17c12f0 [color=SEL_ARG::BLACK, is_asc=true, minflag=4 '\004', maxflag=8 '\b', part=1 '\001', selectivity=1]
| | | field = $d14 (Item_field *) 0x7f7cf0444ab0 field = test.tmp_sel_arg1.kp2
| | | scope = ( -infinity, $d15 (Item_int *) 0x7f7cf0d96b70 value = 4 )
| |--$d18 (SEL_ARG *) 0x7f7cf17c10b0 [color=SEL_ARG::BLACK, is_asc=true, minflag=0 '\000', maxflag=0 '\000', part=0 '\000', selectivity=1]
| | | field = $d19 (Item_field *) 0x7f7cf0444938 field = test.tmp_sel_arg1.kp1
| | | equal = [ $d20 (Item_int *) 0x7f7cf0d96668 value = 4 ]
| | |--$d22 (SEL_ARG *) 0x7f7cf17c0f90 [color=SEL_ARG::RED, is_asc=true, minflag=0 '\000', maxflag=0 '\000', part=0 '\000', selectivity=1]
| | | | field = $d23 (Item_field *) 0x7f7cf0444938 field = test.tmp_sel_arg1.kp1
| | | | equal = [ $d24 (Item_int *) 0x7f7cf0d96558 value = 3 ]
| | | `--$d28 (SEL_ROOT *) 0x7f7cf17c1370 [type=SEL_ROOT::Type::KEY_RANGE, use_count=5, elements=1]
| | | `--$d29 (SEL_ARG *) 0x7f7cf17c12f0 [color=SEL_ARG::BLACK, is_asc=true, minflag=4 '\004', maxflag=8 '\b', part=1 '\001', selectivity=1]
| | | | field = $d30 (Item_field *) 0x7f7cf0444ab0 field = test.tmp_sel_arg1.kp2
| | | | scope = ( -infinity, $d31 (Item_int *) 0x7f7cf0d96b70 value = 4 )
| | |--$d34 (SEL_ARG *) 0x7f7cf17c11d0 [color=SEL_ARG::RED, is_asc=true, minflag=0 '\000', maxflag=0 '\000', part=0 '\000', selectivity=1]
| | | | field = $d35 (Item_field *) 0x7f7cf0444938 field = test.tmp_sel_arg1.kp1
| | | | equal = [ $d36 (Item_int *) 0x7f7cf0d96778 value = 5 ]
| | | `--$d40 (SEL_ROOT *) 0x7f7cf17c1370 [type=SEL_ROOT::Type::KEY_RANGE, use_count=5, elements=1]
| | | `--$d41 (SEL_ARG *) 0x7f7cf17c12f0 [color=SEL_ARG::BLACK, is_asc=true, minflag=4 '\004', maxflag=8 '\b', part=1 '\001', selectivity=1]
| | | | field = $d42 (Item_field *) 0x7f7cf0444ab0 field = test.tmp_sel_arg1.kp2
| | | | scope = ( -infinity, $d43 (Item_int *) 0x7f7cf0d96b70 value = 4 )
| | `--$d46 (SEL_ROOT *) 0x7f7cf17c1370 [type=SEL_ROOT::Type::KEY_RANGE, use_count=5, elements=1]
| | `--$d47 (SEL_ARG *) 0x7f7cf17c12f0 [color=SEL_ARG::BLACK, is_asc=true, minflag=4 '\004', maxflag=8 '\b', part=1 '\001', selectivity=1]
| | | field = $d48 (Item_field *) 0x7f7cf0444ab0 field = test.tmp_sel_arg1.kp2
| | | scope = ( -infinity, $d49 (Item_int *) 0x7f7cf0d96b70 value = 4 )
| `--$d52 (SEL_ROOT *) 0x7f7cf17c1370 [type=SEL_ROOT::Type::KEY_RANGE, use_count=5, elements=1]
| `--$d53 (SEL_ARG *) 0x7f7cf17c12f0 [color=SEL_ARG::BLACK, is_asc=true, minflag=4 '\004', maxflag=8 '\b', part=1 '\001', selectivity=1]
| | field = $d54 (Item_field *) 0x7f7cf0444ab0 field = test.tmp_sel_arg1.kp2
| | scope = ( -infinity, $d55 (Item_int *) 0x7f7cf0d96b70 value = 4 )
`--$d58 (SEL_ROOT *) 0x7f7cf17c1420 [type=SEL_ROOT::Type::KEY_RANGE, use_count=1, elements=1]
`--$d59 (SEL_ARG *) 0x7f7cf17c13a0 [color=SEL_ARG::BLACK, is_asc=true, minflag=4 '\004', maxflag=8 '\b', part=0 '\000', selectivity=1]
| field = $d60 (Item_field *) 0x7f7cf0444ab0 field = test.tmp_sel_arg1.kp2
| scope = ( -infinity, $d61 (Item_int *) 0x7f7cf0d96b70 value = 4 ) 對于IN values
foreach op->arguments
tree_or (get_mm_parts) NOT IN是有可能把記憶體oom的，是以not in的個數收到NOT_IN_IGNORE_THRESHOLD的控制，小于這個門檻值，建立mmtree，否則傳回null
const uint NOT_IN_IGNORE_THRESHOLD = 1000; // If we have t.key NOT IN (null, null, ...) or the list is too long select * from tmp_sel_arg1 where kp1 not in (1, 2, 3, 4, 5)
(gdb) my st tree
$b0 (SEL_TREE *) 0x7f7cf040acd0 [type=SEL_TREE::KEY,keys.m_size=1]
`--$b1 (SEL_ROOT *) 0x7f7cf040adc8 [type=SEL_ROOT::Type::KEY_RANGE, use_count=1, elements=6]
`--$b2 (SEL_ARG *) 0x7f7cf040ae68 [color=SEL_ARG::BLACK, is_asc=true, minflag=4 '\004', maxflag=8 '\b', part=0 '\000', selectivity=1]
| field = $b3 (Item_field *) 0x7f7cf0446438 field = test.tmp_sel_arg1.kp1
| scope = ( $b4 (Item_int *) 0x7f7cf04add58 value = 5, $b5 (Item_int *) 0x7f7cf04add58 value = 5 )
|--$b6 (SEL_ARG *) 0x7f7cf040ad48 [color=SEL_ARG::BLACK, is_asc=true, minflag=4 '\004', maxflag=8 '\b', part=0 '\000', selectivity=1]
| | field = $b7 (Item_field *) 0x7f7cf0446438 field = test.tmp_sel_arg1.kp1
| | scope = ( -infinity, $b8 (Item_int *) 0x7f7cf04add58 value = 5 )
`--$b11 (SEL_ARG *) 0x7f7cf040b0a8 [color=SEL_ARG::RED, is_asc=true, minflag=4 '\004', maxflag=8 '\b', part=0 '\000', selectivity=1]
| field = $b12 (Item_field *) 0x7f7cf0446438 field = test.tmp_sel_arg1.kp1
| scope = ( $b13 (Item_int *) 0x7f7cf04add58 value = 5, $b14 (Item_int *) 0x7f7cf04add58 value = 5 )
|--$b15 (SEL_ARG *) 0x7f7cf040af88 [color=SEL_ARG::BLACK, is_asc=true, minflag=4 '\004', maxflag=8 '\b', part=0 '\000', selectivity=1]
| | field = $b16 (Item_field *) 0x7f7cf0446438 field = test.tmp_sel_arg1.kp1
| | scope = ( $b17 (Item_int *) 0x7f7cf04add58 value = 5, $b18 (Item_int *) 0x7f7cf04add58 value = 5 )
`--$b21 (SEL_ARG *) 0x7f7cf040b1c8 [color=SEL_ARG::BLACK, is_asc=true, minflag=4 '\004', maxflag=8 '\b', part=0 '\000', selectivity=1]
| field = $b22 (Item_field *) 0x7f7cf0446438 field = test.tmp_sel_arg1.kp1
| scope = ( $b23 (Item_int *) 0x7f7cf04add58 value = 5, $b24 (Item_int *) 0x7f7cf04add58 value = 5 )
`--$b26 (SEL_ARG *) 0x7f7cf040b2e8 [color=SEL_ARG::RED, is_asc=true, minflag=4 '\004', maxflag=2 '\002', part=0 '\000', selectivity=1]
| field = $b27 (Item_field *) 0x7f7cf0446438 field = test.tmp_sel_arg1.kp1
| scope = ( $b28 (Item_int *) 0x7f7cf04add58 value = 5, +infinity ) 記錄NOT IN的變量，is_negated = true
t.key NOT IN (c1, c2, ...), c{i} are constants.
=>
($MIN get_mm_leaf 函數
構造SEL_ROOT結構
tree_and 函數
周遊所有keys，通過key_and合并 tree1和tree2
for (uint idx = 0; idx < param->keys; idx++) {
key_and // Produce a SEL_ARG graph that represents "key1 AND key2"
} tree_or 函數
周遊所有keys，通過key_or合并 tree1和tree2
a) 可能産生簡單的range (in tree->keys[])
b) 可能産生index merge range(in tree->merges)
for (uint idx = 0; idx < param->keys; idx++) {
key_or
} key_and 函數
盡可能合并 SEL_ARG "key1 AND key2" .
kp1 > 1 and kp1 < 5 (sel_arg1(min_value=1) and sel_arg2(max_value=5))
----> 1 < kp1 < 5 (new_sel_arg(min_value=1, max_value=5))
kp1 > 1 and kp1 > 5 (sel_arg1(min_value=1) and sel_arg2(min_value=5))
----> kp1 > 5 (new_sel_arg(min_value=5))
key_or 函數
盡可能合并 SEL_ARG "key1 OR key2" .
=> expr1 OR expr2.
對于重疊的子範圍，遞歸調用key_or：
(1) ( 1 < kp1 < 10 AND 1 < kp2 < 10 )
(2) ( 2 < kp1 < 20 AND 4 < kp2 < 20 )
key_or( 1 < kp2 < 10, 4 < kp2 < 20 ) => 1 < kp2 < 2
Range 概念
Notation for illustrations used in the rest of this function:
Range: [--------]
^ ^
start stop
Two overlapping ranges:
[-----] [----] [--]
[---] or [---] or [-------]
Ambiguity: ***
The range starts or stops somewhere in the "***" range.
Example: a starts before b and may end before/the same place/after b
a: [----***]
b: [---]
Adjacent ranges:
Ranges that meet but do not overlap. Example: a = "x < 3", b = "x >= 3"
a: ----]
b: [---- 比較函數cmp_xxx_to_yyy {xxx|yyy = min|max}
find_range-->cmp_min_to_min
initialize cur_key1 to the latest range in key1 that starts the
same place or before the range in cur_key2 starts
cur_key2: [------]
key1: [---] [-----] [----]
^
cur_key1
Used to describe how two key values are positioned compared to
each other. Consider key_value_a.(key_value_b):
-2: key_value_a is smaller than key_value_b, and they are adjacent
-1: key_value_a is smaller than key_value_b (not adjacent)
0: the key values are equal
1: key_value_a is bigger than key_value_b (not adjacent)
2: key_value_a is bigger than key_value_b, and they are adjacent
Example: "cmp= cur_key1->cmp_max_to_min(cur_key2)"
cur_key2: [-------- (10 <= x ... )
cur_key1: -----] ( ... x < 10) => cmp==-2
cur_key1: ----] ( ... x < 9) => cmp==-1
cur_key1: ------] ( ... x <= 10) => cmp== 0
cur_key1: --------] ( ... x <= 12) => cmp== 1
(cmp == 2 does not make sense for cmp_max_to_min())
典型的例子和處理邏輯：
Some typical examples:
1. explain select * from tmp_sel_arg where kp1 between 1 and 10 or kp1 between 0 and 20;
cur_key2: [--------]
key1: [****--] [----] [-------]
^
cur_key1
2. explain select * from tmp_sel_arg where kp1 between 1 and 10 or kp1 between 10 and 20;
This is the case:
cur_key2: [-------]
cur_key1: [----]
Result:
cur_key2: [-------------] => inserted into key1 below
cur_key1: => deleted
(gdb) my sel key1
$p0 (SEL_ROOT *) 0x7f7cf17c0f48 [type=SEL_ROOT::Type::KEY_RANGE, use_count=0, elements=1]
`--$p1 (SEL_ARG *) 0x7f7cf17c0ec8 [color=SEL_ARG::BLACK, is_asc=true, minflag=0 '\000', maxflag=0 '\000', part=0 '\000', selectivity=1]
| field = $p2 (Item_field *) 0x7f7cf0444df0 field = test.tmp_sel_arg.kp1
| scope = [ $p3 (Item_int *) 0x7f7cf0d96340 value = 1, $p4 (Item_int *) 0x7f7cf0d96440 value = 10 ]
(gdb) my sel key2
$q0 (SEL_ROOT *) 0x7f7cf17c1220 [type=SEL_ROOT::Type::KEY_RANGE, use_count=0, elements=1]
`--$q1 (SEL_ARG *) 0x7f7cf17c11a0 [color=SEL_ARG::BLACK, is_asc=true, minflag=0 '\000', maxflag=0 '\000', part=0 '\000', selectivity=1]
| field = $q2 (Item_field *) 0x7f7cf0444f68 field = test.tmp_sel_arg.kp1
| scope = [ $q3 (Item_int *) 0x7f7cf0d969a0 value = 10, $q4 (Item_int *) 0x7f7cf0d96aa0 value = 20 ]
8838 SEL_ROOT *new_key = key_or(param, key1, key2);
(gdb) my sel new_key
$r0 (SEL_ROOT *) 0x7f7cf17c0f48 [type=SEL_ROOT::Type::KEY_RANGE, use_count=0, elements=1]
`--$r1 (SEL_ARG *) 0x7f7cf17c0ec8 [color=SEL_ARG::BLACK, is_asc=true, minflag=0 '\000', maxflag=0 '\000', part=0 '\000', selectivity=1]
| field = $r2 (Item_field *) 0x7f7cf0444df0 field = test.tmp_sel_arg.kp1
| scope = [ $r3 (Item_int *) 0x7f7cf0d96340 value = 1, $r4 (Item_int *) 0x7f7cf0d96aa0 value = 20 ]
3. explain select * from tmp_sel_arg where kp1 between 1 and 10 and kp2 > 1 or kp1 between 10 and 20 and kp2 > 1;
Adjacent ranges with equal next_key_part. Merge like this:
This is the case:
cur_key2: [------]
cur_key1: [-----]
Result:
cur_key2: [------]
cur_key1: [-------------] ? TODO:daoke.wangc why key2 is not deleted
$u0 (SEL_TREE *) 0x7f7cf040ac90 [type=SEL_TREE::KEY,keys.m_size=1]
`--$u1 (SEL_ROOT *) 0x7f7cf040af48 [type=SEL_ROOT::Type::KEY_RANGE, use_count=1, elements=2]
`--$u2 (SEL_ARG *) 0x7f7cf040aec8 [color=SEL_ARG::BLACK, is_asc=true, minflag=0 '\000', maxflag=0 '\000', part=0 '\000', selectivity=1]
| field = $u3 (Item_field *) 0x7f7cf04b09e0 field = test.tmp_sel_arg.kp1
| scope = [ $u4 (Item_int *) 0x7f7cf04af218 value = 10, $u5 (Item_int *) 0x7f7cf04af318 value = 20 ]
|--$u6 (SEL_ARG *) 0x7f7cf040b470 [color=SEL_ARG::RED, is_asc=true, minflag=0 '\000', maxflag=8 '\b', part=0 '\000', selectivity=1]
| | field = $u7 (Item_field *) 0x7f7cf04b09e0 field = test.tmp_sel_arg.kp1
| | scope = [ $u8 (Item_int *) 0x7f7cf04ae6f0 value = 1, $u9 (Item_int *) 0x7f7cf04af218 value = 10 )
| `--$u12 (SEL_ROOT *) 0x7f7cf040b060 [type=SEL_ROOT::Type::KEY_RANGE, use_count=1, elements=1]
| `--$u13 (SEL_ARG *) 0x7f7cf040afe0 [color=SEL_ARG::BLACK, is_asc=true, minflag=4 '\004', maxflag=2 '\002', part=1 '\001', selectivity=1]
| | field = $u14 (Item_field *) 0x7f7cf04b0b58 field = test.tmp_sel_arg.kp2
| | scope = ( $u15 (Item_int *) 0x7f7cf04aed50 value = 1, +infinity )
`--$u19 (SEL_ROOT *) 0x7f7cf040b570 [type=SEL_ROOT::Type::KEY_RANGE, use_count=1, elements=1]
`--$u20 (SEL_ARG *) 0x7f7cf040b4f0 [color=SEL_ARG::BLACK, is_asc=true, minflag=4 '\004', maxflag=2 '\002', part=1 '\001', selectivity=1]
| field = $u21 (Item_field *) 0x7f7cf04b0b58 field = test.tmp_sel_arg.kp2
| scope = ( $u22 (Item_int *) 0x7f7cf04aed50 value = 1, +infinity )
4. explain select * from tmp_sel_arg where kp1 between 30 and 50 and kp2 > 1 or kp1 between 60 and 120 and kp2 > 20 or kp1 between 10 and 100 and kp2 > 1;
cur_key2: [****----------------------*******]
key1: [--] [----] [---] [-----] [xxxx]
^ ^ ^
first last different next_key_part
Result:
cur_key2: [****----------------------*******]
[--] [----] [---] => deleted from key1
key1: [**------------------------***][xxxx]
^ ^
cur_key1=last different next_key_part
$ab0 (SEL_TREE *) 0x7f7cf17c0c90 [type=SEL_TREE::KEY,keys.m_size=1]
`--$ab1 (SEL_ROOT *) 0x7f7cf17c0f48 [type=SEL_ROOT::Type::KEY_RANGE, use_count=1, elements=3]
`--$ab2 (SEL_ARG *) 0x7f7cf17c1860 [color=SEL_ARG::BLACK, is_asc=true, minflag=0 '\000', maxflag=0 '\000', part=0 '\000', selectivity=1]
| field = $ab3 (Item_field *) 0x7f7cf0446718 field = test.tmp_sel_arg.kp1
| scope = [ $ab4 (Item_int *) 0x7f7cf0d96ee8 value = 60, $ab5 (Item_int *) 0x7f7cf0444cd0 value = 100 ]
|--$ab6 (SEL_ARG *) 0x7f7cf17c0ec8 [color=SEL_ARG::RED, is_asc=true, minflag=0 '\000', maxflag=8 '\b', part=0 '\000', selectivity=1]
| | field = $ab7 (Item_field *) 0x7f7cf0446228 field = test.tmp_sel_arg.kp1
| | scope = [ $ab8 (Item_int *) 0x7f7cf0444bd0 value = 10, $ab9 (Item_int *) 0x7f7cf0d96ee8 value = 60 )
| `--$ab12 (SEL_ROOT *) 0x7f7cf17c1060 [type=SEL_ROOT::Type::KEY_RANGE, use_count=1, elements=1]
| `--$ab13 (SEL_ARG *) 0x7f7cf17c0fe0 [color=SEL_ARG::BLACK, is_asc=true, minflag=4 '\004', maxflag=2 '\002', part=1 '\001', selectivity=1]
| | field = $ab14 (Item_field *) 0x7f7cf04463a0 field = test.tmp_sel_arg.kp2
| | scope = ( $ab15 (Item_int *) 0x7f7cf0d96a20 value = 1, +infinity )
|--$ab18 (SEL_ARG *) 0x7f7cf17c12b8 [color=SEL_ARG::RED, is_asc=true, minflag=4 '\004', maxflag=0 '\000', part=0 '\000', selectivity=1]
| | field = $ab19 (Item_field *) 0x7f7cf0446718 field = test.tmp_sel_arg.kp1
| | scope = ( $ab20 (Item_int *) 0x7f7cf0444cd0 value = 100, $ab21 (Item_int *) 0x7f7cf0444028 value = 120 ]
| `--$ab24 (SEL_ROOT *) 0x7f7cf17c1450 [type=SEL_ROOT::Type::KEY_RANGE, use_count=1, elements=1]
| `--$ab25 (SEL_ARG *) 0x7f7cf17c13d0 [color=SEL_ARG::BLACK, is_asc=true, minflag=4 '\004', maxflag=2 '\002', part=1 '\001', selectivity=1]
| | field = $ab26 (Item_field *) 0x7f7cf0446890 field = test.tmp_sel_arg.kp2
| | scope = ( $ab27 (Item_int *) 0x7f7cf0444588 value = 20, +infinity )
`--$ab30 (SEL_ROOT *) 0x7f7cf17c1960 [type=SEL_ROOT::Type::KEY_RANGE, use_count=1, elements=1]
`--$ab31 (SEL_ARG *) 0x7f7cf17c18e0 [color=SEL_ARG::BLACK, is_asc=true, minflag=4 '\004', maxflag=2 '\002', part=1 '\001', selectivity=1]
| field = $ab32 (Item_field *) 0x7f7cf0446890 field = test.tmp_sel_arg.kp2
| scope = ( $ab33 (Item_int *) 0x7f7cf0445230 value = 1, +infinity )
5. with next_key_part and not
This is the case:
cur_key2: [-------]
cur_key1: [---------]
Result:
cur_key2: deleted
cur_key1: [------------]
explain select * from tmp_sel_arg where kp1 between 5 and 15 or kp1 between 10 and 30;
$ae0 (SEL_TREE *) 0x7f7cf040ac90 [type=SEL_TREE::KEY,keys.m_size=1]
`--$ae1 (SEL_ROOT *) 0x7f7cf040af48 [type=SEL_ROOT::Type::KEY_RANGE, use_count=1, elements=1]
`--$ae2 (SEL_ARG *) 0x7f7cf040aec8 [color=SEL_ARG::BLACK, is_asc=true, minflag=0 '\000', maxflag=0 '\000', part=0 '\000', selectivity=1]
| field = $ae3 (Item_field *) 0x7f7cf0444df0 field = test.tmp_sel_arg.kp1
| scope = [ $ae4 (Item_int *) 0x7f7cf0d96340 value = 5, $ae5 (Item_int *) 0x7f7cf0d96aa0 value = 30 ]
This is the case:
cur_key2: [-------]
cur_key1: [---------]
Result:
cur_key2: [---]
cur_key1: [---------]
explain select * from tmp_sel_arg where kp1 between 5 and 15 and kp2 > 1 or kp1 between 10 and 30 and kp2 > 1;
$ad0 (SEL_TREE *) 0x7f7cf17c0c90 [type=SEL_TREE::KEY,keys.m_size=1]
`--$ad1 (SEL_ROOT *) 0x7f7cf17c0f48 [type=SEL_ROOT::Type::KEY_RANGE, use_count=1, elements=2]
`--$ad2 (SEL_ARG *) 0x7f7cf17c0ec8 [color=SEL_ARG::BLACK, is_asc=true, minflag=0 '\000', maxflag=0 '\000', part=0 '\000', selectivity=1]
| field = $ad3 (Item_field *) 0x7f7cf04b09e0 field = test.tmp_sel_arg.kp1
| scope = [ $ad4 (Item_int *) 0x7f7cf04af218 value = 10, $ad5 (Item_int *) 0x7f7cf04af318 value = 30 ]
|--$ad6 (SEL_ARG *) 0x7f7cf17c1470 [color=SEL_ARG::RED, is_asc=true, minflag=0 '\000', maxflag=8 '\b', part=0 '\000', selectivity=1]
| | field = $ad7 (Item_field *) 0x7f7cf04b09e0 field = test.tmp_sel_arg.kp1
| | scope = [ $ad8 (Item_int *) 0x7f7cf04ae6f0 value = 5, $ad9 (Item_int *) 0x7f7cf04af218 value = 10 )
| `--$ad12 (SEL_ROOT *) 0x7f7cf17c1060 [type=SEL_ROOT::Type::KEY_RANGE, use_count=1, elements=1]
| `--$ad13 (SEL_ARG *) 0x7f7cf17c0fe0 [color=SEL_ARG::BLACK, is_asc=true, minflag=4 '\004', maxflag=2 '\002', part=1 '\001', selectivity=1]
| | field = $ad14 (Item_field *) 0x7f7cf04b0b58 field = test.tmp_sel_arg.kp2
| | scope = ( $ad15 (Item_int *) 0x7f7cf04aed50 value = 1, +infinity )
`--$ad19 (SEL_ROOT *) 0x7f7cf17c1570 [type=SEL_ROOT::Type::KEY_RANGE, use_count=1, elements=1]
`--$ad20 (SEL_ARG *) 0x7f7cf17c14f0 [color=SEL_ARG::BLACK, is_asc=true, minflag=4 '\004', maxflag=2 '\002', part=1 '\001', selectivity=1]
| field = $ad21 (Item_field *) 0x7f7cf04b0b58 field = test.tmp_sel_arg.kp2
| scope = ( $ad22 (Item_int *) 0x7f7cf04aed50 value = 1, +infinity ) 調用堆棧
通過range生成mm tree是在優化階段進行的，目的是計算代價，選擇更優quick通路路徑。
select * from tmp_sel_arg where (kp1=1 and kp2=2 and kp3=3) or (kp1=1 and kp2=2 and kp3=4) or (kp1=1 and kp2=3 and kp3=5) or (kp1=1 and kp2=3 and kp3=6);
#3 0x000000000322ab92 in test_quick_select (thd=0x7f59d160b000, keys_to_use=..., prev_tables=0, limit=18446744073709551615, force_quick_range=false,
interesting_order=ORDER_NOT_RELEVANT, tab=0x7f59cf4dd690, cond=0x7f59d0ee3740, needed_reg=0x7f59cf4dd6e0, quick=0x7f5ad0efa738)
at /flash11/daoke.wangc/PolarDB_80/sql/opt_range.cc:4106
#4 0x0000000003384764 in get_quick_record_count (thd=0x7f59d160b000, tab=0x7f59cf4dd690, limit=18446744073709551615)
at /flash11/daoke.wangc/PolarDB_80/sql/sql_optimizer.cc:5980
#5 0x0000000003383c40 in JOIN::estimate_rowcount (this=0x7f59cf4dbc68) at /flash11/daoke.wangc/PolarDB_80/sql/sql_optimizer.cc:5713
#6 0x000000000338202c in JOIN::make_join_plan (this=0x7f59cf4dbc68) at /flash11/daoke.wangc/PolarDB_80/sql/sql_optimizer.cc:5123
#7 0x0000000003375d5b in JOIN::optimize (this=0x7f59cf4dbc68) at /flash11/daoke.wangc/PolarDB_80/sql/sql_optimizer.cc:688
#8 0x0000000003424076 in SELECT_LEX::optimize (this=0x7f59cf6ad968, thd=0x7f59d160b000) at /flash11/daoke.wangc/PolarDB_80/sql/sql_select.cc:1619
#9 0x00000000034223d2 in Sql_cmd_dml::execute_inner (this=0x7f59cf4db3f0, thd=0x7f59d160b000) at /flash11/daoke.wangc/PolarDB_80/sql/sql_select.cc:753
#10 0x0000000003421d53 in Sql_cmd_dml::execute (this=0x7f59cf4db3f0, thd=0x7f59d160b000) at /flash11/daoke.wangc/PolarDB_80/sql/sql_select.cc:631
#11 0x00000000033a7a71 in mysql_execute_command (thd=0x7f59d160b000, first_level=true) at /flash11/daoke.wangc/PolarDB_80/sql/sql_parse.cc:4897
#12 0x00000000033aa369 in mysql_parse (thd=0x7f59d160b000, parser_state=0x7f5ad0efc6f0, force_primary_storage_engine=false)
at /flash11/daoke.wangc/PolarDB_80/sql/sql_parse.cc:5722
#13 0x000000000339eaeb in dispatch_command (thd=0x7f59d160b000, com_data=0x7f5ad0efd1b0, command=COM_QUERY) at /flash11/daoke.wangc/PolarDB_80/sql/sql_parse.cc:1873
#14 0x000000000339cd7f in do_command(THD*, std::function*) (thd=0x7f59d160b000, dispatcher=0x0)
at /flash11/daoke.wangc/PolarDB_80/sql/sql_parse.cc:1335
#15 0x000000000339cf1d in do_command (thd=0x7f59d160b000) at /flash11/daoke.wangc/PolarDB_80/sql/sql_parse.cc:1372
#16 0x00000000035f4930 in handle_connection (arg=0x7f5ad6180ec0) at /flash11/daoke.wangc/PolarDB_80/sql/conn_handler/connection_handler_per_thread.cc:316
#17 0x000000000506e2f3 in pfs_spawn_thread (arg=0x7f5ad628aa20) at /flash11/daoke.wangc/PolarDB_80/storage/perfschema/pfs.cc:2879
#18 0x00007f5af4027e25 in start_thread () from /lib64/libpthread.so.0
#19 0x00007f5af291df1d in clone () from /lib64/libc.so.6 test_quick_select 函數
test_quick_select用來根據範圍選擇索引是否有很快的代價最低的通路方式
步驟如下:
0. prepare potential ranges scan index/keyparts
1. setup_range_conditions
tree = get_mm_tree(¶m, cond);
2. Fix the selectivity for SEL_ARGs by histogram
fix_sel_tree_selectivity(¶m, tree);
3. Try to construct a QUICK_GROUP_MIN_MAX_SELECT
group_trp = get_best_group_min_max(¶m, tree, &best_cost);
4. Try to construnct a QUICK_SKIP_SCAN_SELECT
skip_scan_trp = get_best_skip_scan(¶m, tree, force_skip_scan);
5. Get best 'range' plan and prepare data for making other plans
range_trp = get_key_scans_params(¶m, tree, false, true, &best_cost)
6. Get best non-covering ROR-intersection plan and prepare data for building covering ROR-intersection.
rori_trp = get_best_ror_intersect(¶m, tree, &best_cost, true)
7. Try creating index_merge/ROR-union scan.
new_conj_trp = get_best_disjunct_quick(¶m, imerge, &best_cost);
8. If we got a read plan, create a quick select from it.
qck = best_trp->make_quick(¶m, true) get_key_scans_params 函數
擷取最佳的range掃描方式
for (idx = 0; idx < param->keys; idx++) {
key = tree->keys[idx];
check_quick_select
find best trp
} check_quick_select 函數
根據已知索引key，周遊對應SEL_ARG mm tree，計算所有range索引掃描的rows用來計算代價
ha_innobase::multi_range_read_info_const
for every range in key RB tree
get the next interval in the R-B tree
rows += ha_innobase/ha_innopart::records_in_range
n_ranges++ RANGE_SEQ_IF seq_if = {sel_arg_range_seq_init, sel_arg_range_seq_next, 0, 0};
MRR range sequence, SEL_ARG* implementation: SEL_ARG graph traversal context
Consider a query with these range predicates:
(kp0=1 and kp1=2 and kp2=3) or
(kp0=1 and kp1=2 and kp2=4) or
(kp0=1 and kp1=3 and kp2=5) or
(kp0=1 and kp1=3 and kp2=6)
1) sel_arg_range_seq_next() is called the first time
- traverse the R-B tree (see SEL_ARG) to find the first range
- returns range "1:2:3"
- values in stack after this: stack[1, 1:2, 1:2:3]
2) sel_arg_range_seq_next() is called second time
- keypart 2 has another range, so the next range in
keypart 2 is appended to stack[1] and saved
in stack[2]
- returns range "1:2:4"
- values in stack after this: stack[1, 1:2, 1:2:4]
3) sel_arg_range_seq_next() is called the third time
- no more ranges in keypart 2, but keypart 1 has
another range, so the next range in keypart 1 is
appended to stack[0] and saved in stack[1]. The first
range in keypart 2 is then appended to stack[1] and
saved in stack[2]
- returns range "1:3:5"
- values in stack after this: stack[1, 1:3, 1:3:5]
4) sel_arg_range_seq_next() is called the fourth time
- keypart 2 has another range, see 2)
- returns range "1:3:6"
- values in stack after this: stack[1, 1:3, 1:3:6] Quick Read Plan 結構函數
/*
Table rows retrieval plan. Range optimizer creates QUICK_SELECT_I-derived
objects from table read plans.
*/
class TABLE_READ_PLAN {
......
}
/*
Plan for a QUICK_RANGE_SELECT scan.
TRP_RANGE::make_quick ignores retrieve_full_rows parameter because
QUICK_RANGE_SELECT doesn't distinguish between 'index only' scans and full
record retrieval scans.
*/
class TRP_RANGE : public TABLE_READ_PLAN {
......
SEL_ROOT *key;
......
}
class TRP_ROR_INTERSECT : public TABLE_READ_PLAN {
......
}
/*
Plan for QUICK_ROR_UNION_SELECT scan.
QUICK_ROR_UNION_SELECT always retrieves full rows, so retrieve_full_rows
is ignored by make_quick.
*/
class TRP_ROR_UNION : public TABLE_READ_PLAN {
......
}
/*
Plan for QUICK_INDEX_MERGE_SELECT scan.
QUICK_ROR_INTERSECT_SELECT always retrieves full rows, so retrieve_full_rows
is ignored by make_quick.
*/
class TRP_INDEX_MERGE : public TABLE_READ_PLAN {
......
}
/*
Plan for a QUICK_GROUP_MIN_MAX_SELECT scan.
*/
class TRP_GROUP_MIN_MAX : public TABLE_READ_PLAN {
......
}
/*
Plan for a QUICK_SKIP_SCAN_SELECT scan.
*/
class TRP_SKIP_SCAN : public TABLE_READ_PLAN {
......
} 生成對應的quick執行個體，QEP->quick = TRP_RANGE::make_quick()
GDB分析工具
https://github.com/cwang82566/mysql_debugging_tools.gitselect * from tmp_sel_arg1 where (kp1=1 and kp2=2 and kp3=3) or (kp1=1 and kp2=2 and kp3=4) or (kp1=1 and kp2=3 and kp3=5) or (kp1=1 and kp2=3 and kp3=6);
(gdb) my st tree
$c0 (SEL_TREE *) 0x7f7cf040acd0 [type=SEL_TREE::KEY,keys.m_size=2]
|--$c1 (SEL_ROOT *) 0x7f7cf040add0 [type=SEL_ROOT::Type::KEY_RANGE, use_count=1, elements=3]
| `--$c2 (SEL_ARG *) 0x7f7cf040b800 [color=SEL_ARG::BLACK, is_asc=true, minflag=0 '\000', maxflag=0 '\000', part=0 '\000', selectivity=1]
| | field = $c3 (Item_field *) 0x7f7cf04c1508 field = test.tmp_sel_arg1.kp1
| | equal = [ $c4 (Item_int *) 0x7f7cf04af718 value = 2 ]
| |--$c6 (SEL_ARG *) 0x7f7cf040ad50 [color=SEL_ARG::RED, is_asc=true, minflag=4 '\004', maxflag=8 '\b', part=0 '\000', selectivity=1]
| | | field = $c7 (Item_field *) 0x7f7cf04c0728 field = test.tmp_sel_arg1.kp1
| | | scope = ( -infinity, $c8 (Item_int *) 0x7f7cf04ae760 value = 1 )
| | `--$c11 (SEL_ROOT *) 0x7f7cf040b3d0 [type=SEL_ROOT::Type::KEY_RANGE, use_count=1, elements=1]
| | `--$c12 (SEL_ARG *) 0x7f7cf040b350 [color=SEL_ARG::BLACK, is_asc=true, minflag=0 '\000', maxflag=0 '\000', part=1 '\001', selectivity=1]
| | | field = $c13 (Item_field *) 0x7f7cf04c0aa0 field = test.tmp_sel_arg1.kp2
| | | equal = [ $c14 (Item_int *) 0x7f7cf04aea80 value = 5 ]
| | `--$c18 (SEL_ROOT *) 0x7f7cf040aef8 [type=SEL_ROOT::Type::KEY_RANGE, use_count=1, elements=2]
| | `--$c19 (SEL_ARG *) 0x7f7cf040ae78 [color=SEL_ARG::BLACK, is_asc=true, minflag=0 '\000', maxflag=0 '\000', part=2 '\002', selectivity=1]
| | | field = $c20 (Item_field *) 0x7f7cf04c0e18 field = test.tmp_sel_arg1.kp3
| | | equal = [ $c21 (Item_int *) 0x7f7cf04aef48 value = 10 ]
| | `--$c24 (SEL_ARG *) 0x7f7cf040b040 [color=SEL_ARG::RED, is_asc=true, minflag=0 '\000', maxflag=0 '\000', part=2 '\002', selectivity=1]
| | | field = $c25 (Item_field *) 0x7f7cf04c1190 field = test.tmp_sel_arg1.kp3
| | | equal = [ $c26 (Item_int *) 0x7f7cf04af268 value = 12 ]
| |--$c30 (SEL_ARG *) 0x7f7cf04370c8 [color=SEL_ARG::RED, is_asc=true, minflag=0 '\000', maxflag=0 '\000', part=0 '\000', selectivity=1]
| | | field = $c31 (Item_field *) 0x7f7cf04c1f70 field = test.tmp_sel_arg1.kp1
| | | equal = [ $c32 (Item_int *) 0x7f7cf04b0520 value = 3 ]
| | `--$c36 (SEL_ROOT *) 0x7f7cf040b9a0 [type=SEL_ROOT::Type::KEY_RANGE, use_count=1, elements=2]
| | `--$c37 (SEL_ARG *) 0x7f7cf040b920 [color=SEL_ARG::BLACK, is_asc=true, minflag=0 '\000', maxflag=0 '\000', part=2 '\002', selectivity=1]
| | | field = $c38 (Item_field *) 0x7f7cf04c22e8 field = test.tmp_sel_arg1.kp3
| | | equal = [ $c39 (Item_int *) 0x7f7cf04b0840 value = 11 ]
| | `--$c42 (SEL_ARG *) 0x7f7cf040bae8 [color=SEL_ARG::RED, is_asc=true, minflag=0 '\000', maxflag=0 '\000', part=2 '\002', selectivity=1]
| | | field = $c43 (Item_field *) 0x7f7cf04c2660 field = test.tmp_sel_arg1.kp3
| | | equal = [ $c44 (Item_decimal *) 0x7f7cf04b0b60 value = 14 ]
| `--$c48 (SEL_ROOT *) 0x7f7cf040b4f0 [type=SEL_ROOT::Type::KEY_RANGE, use_count=1, elements=2]
| `--$c49 (SEL_ARG *) 0x7f7cf040b470 [color=SEL_ARG::BLACK, is_asc=true, minflag=0 '\000', maxflag=0 '\000', part=2 '\002', selectivity=1]
| | field = $c50 (Item_field *) 0x7f7cf04c1880 field = test.tmp_sel_arg1.kp3
| | equal = [ $c51 (Item_int *) 0x7f7cf04afa38 value = 11 ]
| `--$c54 (SEL_ARG *) 0x7f7cf040b638 [color=SEL_ARG::RED, is_asc=true, minflag=0 '\000', maxflag=0 '\000', part=2 '\002', selectivity=1]
| | field = $c55 (Item_field *) 0x7f7cf04c1bf8 field = test.tmp_sel_arg1.kp3
| | equal = [ $c56 (Item_int *) 0x7f7cf04afd58 value = 14 ]
`--$c60 (SEL_ROOT *) 0x0 Non ![SQL優化SQL語句優化的目的[圖]](data:image/gif;base64,R0lGODlhAQABAIAAAP///wAAACwAAAAAAQABAAACAkQBADs=)