MySQL source code: data structure related to the Range access method-continued

The previous article focuses on how the WHERE condition of MySQL constructs the corresponding SEL_ARG structure for a single index. This article is a supplement and will briefly introduce the SEL_TREE structure corresponding to Multiple indexes. For a complete WHERE condition, MySQL traverses all available indexes and constructs the corresponding SEL_ARG structure one by one. All SEL_ARG structures are pointer arrays.

The previous article focuses on how the WHERE condition of MySQL constructs the corresponding SEL_ARG structure for a single index. This article is a supplement and will briefly introduce the SEL_TREE structure corresponding to Multiple indexes. For a complete WHERE condition, MySQL traverses all available indexes and constructs the corresponding SEL_ARG structure one by one. All SEL_ARG structures are pointer arrays.

The previous article focuses on how the WHERE condition of MySQL targetsSingleIndex construction corresponds to the SEL_ARG structure. This article is a supplement to briefly introduce the SEL_TREE structure of Multiple indexes.

For a complete WHERE condition, MySQL traverses all available indexes and constructs the corresponding SEL_ARG structure one by one, all SEL_ARG structures are stored in SEL_TREE-> keys as pointer arrays. If the corresponding index cannot construct SEL_ARG, the corresponding pointer is null.

class SEL_TREE :public Sql_alloc{...  SEL_ARG *keys[MAX_KEY];...};

Gdb prints the corresponding structure:

(gdb) p $1$2 = (SEL_TREE *) 0x7f59c4038348(gdb) p *$1$3 = {...  keys = {0x0, 0x7f59c4038598, 0x0 },...}

SEL_TREE is an array, but if it is a tree like his name, it will be in the following structure:

                                          [ key1 part1 ]        [ key1 part2 ]            [ key1 part3 ]            -\ /-                                        $                            $              -                         / SEL_ARG(-∞, 1) $ ===>  SEL_ARG  [5,5] ===>  $ SEL_ARG [10,10]              |......                   |        |^      $                            $        |^              |                         |    next||      $                            $    next||        ......|                         |        ||prev  $                            $        ||prev    0x0       |              /--------->|        ||      $                            $        v      \       |              |          |        ||      $                            $ SEL_ARG [12,12]       \------|              |          |        ||      $                            $        [key4]|              |          |        v|      $                            $              |              |          | SEL_ARG [2, 2] $=== next_key_part =====|    $              |      [link of SEL_ARG]  |        |^      $                       |    $              |         /               |    next||      $                       |    $              |--------/                |        ||prev  $                       |===>$ SEL_ARG[11,11]              | [key3]                  |        v|      $                       |    $         |^              |                         \ SEL_ARG [3, 3] $=== next_key_part =====|    $     next||              |                                          $                            $         ||prev              |                                          $                            $         v|              |                                                                      SEL_ARG[14,14]  [SEL_ARG]   |     *************************      \       |     * structure of SEL_TREE *       \------|     *************************        [key2]|              |              |                           [ key1 part1 ]              |                         / SEL_ARG (-∞,2]  $            SEL_ARG [3,5)              |                         |        |^       $                /\ Black              |                         |    next||       $               /  \              |      [link of SEL_ARG]  |        ||prev   $              /    \              |         /     |         |        v|       $ SEL_ARG (-∞,2]   SEL_ARG (10,∞)              |--------/      |         | SEL_ARG [3,5)   $         Red           Red              | [key1]        |-------->|        |^       $              |                         |    next||       $              |                         |        ||prev   $          SEL_TREE                      |        v|       $                                        \ SEL_ARG (10,∞)  $                                                          $

(Big chart)

That's all. This article is relatively simple.

Original article address: MySQL source code: data structure related to the Range access method -- continued. Thank you for sharing it with the original author.