分析: 给定的sql查询在 idx_track_source_id_created_at_len_parse_result_list 索引上使用了索引查找。要判断是否还存在回表操作,需要检查 Extra 字段。 判断标准: 如果Extra 中包含usingIndex 或 Using Index Condition,则不需要回表。 如果Extra 中包含 Using where 且未出现 Using Index,则存在回表操作。 本例...
通过EXPLaiN 判断查询是否回表 要判断查询是否存在回表操作,可以使用 EXPLAIN 分析查询计划。以下是如何通过 EXPLAIN 输出的 Extra 字段判断: usingIndex:表示出现索引覆盖,查询所需的字段都在索引中,不需要回表。 Using Index Condition:表示使用了索引查找,但需要过滤,因为要过滤的字段不在索引中。不回表。 Using Inde...
Description: Suppose query_connection is executing a SQL with subquery, and stops at sync point BEFORE_RESET_QUERY_PLAN. Then we explain it in another explain_connection: ``` explain format=tree for connection <query_connection id>; ``` mysqld will crash: Assertion `current_thd->lex->using...
ACipheris a method of encryption, where characters, or sometimes words, are substituted for other characters in a set pattern, allowing for arbitrary strings to be enciphered using it. The complexity and strength of ciphers varies, fromone-time padsand (historically)Enigmaas stronger and more ...
32 bit app - how to get 'C:\program files" directory using "Environment.GetFolderPath" 32 bit Application calling 32 bit DLL "An attempt was made to load a program with an incorrect format. (Exception from HRESULT: 0x8007000B)" 4 digit precision- String format 405 method not allowed(p...
1330300800UNIX Timestamp, a standard method of storing absolute time in many computer systems and defined as the number of seconds since 00:00:00 on 1970-01-01 (UTC). The Unix time listed here appears to mistakenly be for2012-02-27, which is also mentioned byRandallin the original transcr...
And yes - I further believe you need to use the newer UEFI mode in order to allow boot from VHD. Older legacy MBR style boot method had no way of specifying a VHD file on an NTFS partition as a boot device I guess... You do not need to create or mount a VHD file... Once ...
Even though volunteers and parents differed in several aspects regarding implementation, process features and tutor characteristics, these differences cannot explain the differential effects. The difficulty uncovering the components responsible for the efficacy of the method is discussed, and implications for ...
But this error can be caused by more than just changing your domain name and improperly configuring the redirects. In this post, I’ll outline what causes “err too many redirects,” how to troubleshoot the error, and, most importantly, how to fix it so y...
One of the greatest mysteries that has enchanted scientists in recent times is how it was possible for chemical structures to become biological systems. Scientists have many theories regarding how chemistry eventually turned into biology, but no conclusi