摘要:

分析mysql对于谓词的处理

DML

表结构:

create table d(d1 int, d2 varchar(2)) engine=innodb;

insert into d values(1, \'d1\');insert into d values(2, \'d2\');insert into d values(null, \'d3\');

查询SQL:

select * from d where d1=1 or d1=2;

谓词执行分析:

本SQL的特点:

1. 最小的条件是d1=1, d1=2
2. 然后or将两个条件匹配起来

执行的调用堆栈:

#0  Item_cond_or::val_int (this=0x7f7edc02b640) at /root/work/trunk/mysql-5.7.41/sql/item_cmpfunc.cc:5803
#1  0x00000000014e0001 in evaluate_join_record (join=0x7f7edc02a600, qep_tab=0x7f7edc02b878) at /root/work/trunk/mysql-5.7.41/sql/sql_executor.cc:1415
#2  0x00000000014df97f in sub_select (join