By Daoke
Conditional queries are widely used in SQL queries. The optimization of complex conditions during execution, such as conditions that are always true or false or can be merged, becomes a crucial factor in efficient queries and performance improvement. Additionally, since indexing is the basic method for accessing data in MySQL and provides faster access, the concept of SARGable (Search ARGument ABLE) has been overlooked as it has become the default and necessary approach. How does MySQL organize complex conditions, calculate the cost of available indexes affected by each range, and determine different efficient ways to utilize indexes in order to select the optimal plan? Furthermore, how does MySQL effectively prune conditions for partitioned tables? All of these aspects are intertwined with a structure called mm tree. Let's unveil its mysteries.
When we solve customer problems, the following examples are used in this article:
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));Source code path: ./sql/ http:// opt_range.cc
It is used to record the graph structures of all selectable indexes on the selected tables and is a forest array for the index column.
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.It is used to record the graph structures of the index range and is a forest tree structure for the index column.
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.
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
}It is used to record the RB tree structures of the index column. There are two representations, internal link and RB tree, and each keypart is connected through next_key_part.
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};
......
}The internal structure of the RB tree is shown in the following example:
(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 |
+--------+A SEL_ROOT graph structure is composed of a set of objects in SEL_ARG. Inside the graph structure, SEL_ARG::next/prev is used to associate the same index column condition "OR", and next_key_part is used to associate different index column conditions "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 |
$ $ +--------+The SEL_ARG flag has a total of 6 bits to record different meanings. The first four refer to 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 NULLget_mm_tree (mm=min_max) Function
The range analysis module is used to find the mm trees of all possible indexes. The constructed ranges may be larger than the original condition ranges. Two simple index columns and conditions are as follows:
"WHERE fld1 > 'x' AND fld2 > 'y'"In this scenario, whether you choose the index of fld1 or the index of fld2, you may read more rows than the final result set.
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);
}You need to consider all equivalent columns and construct multiple 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
Construct the entry function of the mm tree.
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.
}Construct an mm tree for SEL_TREE for <> or NOT BETWEEN condition.
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 )Construct an mm tree through the Item cond.
for (every key part) {
SEL_ROOT root = get_mm_leaf
SEL_TREE tree.root = root
}Construct an mm tree through the IN value.
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 )For IN values
foreach op->arguments
tree_or (get_mm_parts)NOT IN may cause the memory to run out, so the number of NOT IN is controlled by NOT_IN_IGNORE_THRESHOLD. If the number of NOT IN is less than this threshold, mm trees are created. Otherwise, a null is returned.
const uint NOT_IN_IGNORE_THRESHOLD = 1000; // If we have t.key NOT IN (null, null, ...) or the list is too longselect * 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 = ( $b28 (Item_int *) 0x7f7cf04add58 value = 5, +infinity )Record the variables of NOT IN, is_negated=true.
t.key NOT IN (c1, c2, ...), c{i} are constants.
=>
($MINConstruct the SEL_ROOT structure.
Traverse all keys and use the key_and function to merge tree1 and tree2.
for (uint idx = 0; idx < param->keys; idx++) {
key_and // Produce a SEL_ARG graph that represents "key1 AND key2"
}Traverse all keys and use the key_or function to merge tree1 and tree2
a) It is possible to generate a simple range (in tree->keys[]).
b) It is possible to generate an index merge range (in tree->merges).
for (uint idx = 0; idx < param->keys; idx++) {
key_or
}Merge SEL_ARG "key1 AND key2" as much as possible.
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))
Merge SEL_ARG "key1 OR key2" as much as possible.
=> expr1 OR expr2.
For overlapping sub-ranges, recursively call key_or function:
(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
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: [----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())
Some typical examples and processing logic:
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 )The mm tree is generated by range in the optimization phase. The purpose is to calculate the cost and select a quicker access path.
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.6test_quick_select function is used to select whether there is a mode with the fastest speed and the lowest cost to access indexes according to the range.
The steps are as follows:
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 the best scanning mode of range.
for (idx = 0; idx < param->keys; idx++) {
key = tree->keys[idx];
check_quick_select
find best trp
}According to the known index key, traverse the corresponding SEL_ARG mm tree and calculate all the rows scanned by the range index to calculate the cost.
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]/*
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 {
......
}Generate the corresponding quick instance, QEP-> quick=TRP_RANGE::make_quick().
https://github.com/cwang82566/mysql_debugging_tools.git
select * 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 NonBest Practices for Upgrading PolarDB for MySQL 5.6/MySQL 5.6 to PolarDB for MySQL 8.0
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