SHARDING-JDBC Source analysis of database sub-Library sub-table middleware--sql parsing (vi) deleting SQL

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This article is mainly based on SHARDING-JDBC 1.5.0 Official edition

• 1. Overview

• 2. Deletestatement

• 3. #parse ()

  • 3.1 #skipBetweenDeleteAndTable ()

  • 3.2 #parseSingleTable ()

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  • 3.3 #parseWhere ()

• 666. Easter eggs

1. Overview

Before reading this article:

• The lexical analysis of SQL parsing (i)

• SQL Resolution (ii) of SQL

This article shares the removal of SQL parsing source code implementation.

If you already understand SQL Resolution (c) query SQL, then this article will be a hydrology, as a kind of relaxation. As in the text above, take MySQL for example. Let's take a look at Mysqldeleteparser.

There are 2 types of MySQL DELETE syntax:

• The first type:single-table syntax

DELETE [low_priority] [QUICK] [IGNORE] from Tbl_name [PARTITION (Partition_name,...)]    [WHERE Where_condition]    [ORDER by ...] [LIMIT Row_count]

• second:

delete [low_priority] [quick] [ignore]    tbl_name[.*] [, tbl_ Name[.*]] ...    from table_references    [where where_ Condition] "OR" delete [low_priority] [quick] [ignore]    from tbl_name[ .*] [, tbl_name[.*]] ...    using table_references     [where where_condition] 

SHARDING-JDBC currently supports only the first type. Few of the second types of business scenarios are used.

SHARDING-JDBC Update SQL parsing main flow is as follows:

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// [email protected] deletestatement parse ()  {   sqlparser.getlexer () . NextToken (); //  skip  delete   skipbetweendeleteandtable (); // //  Skip keywords, such as  low_priority, ignore , and  from   sqlparser.parsesingletable in:mysql  ( deletestatement); //  Parse table    sqlparser.skipuntil (defaultkeyword.where); //  jump to  where   sqlparser.parsewhere (deletestatement); //  analysis  WHERE    return deletestatement;} 

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2. Deletestatement

Delete the SQL resolution results.

Public final class Updatestatement extends Abstractsqlstatement {}

Yes, there are no other properties.

delete IGNORE from T_user WHERE user_id = parse result :

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3. #parse () 3.1 #skipBetweenDeleteAndTable ()

DELETEThere are some lexical forms between and table names that have no effect on SQL routing and overrides and are skipped.

[email protected] void skipbetweendeleteandtable () {Getsqlparser (). Skipall (Mysqlkeyword.low_priority,   Mysqlkeyword.quick, Mysqlkeyword.ignore); Getsqlparser (). skipifequal (Defaultkeyword.from);}   [email protected] void skipbetweendeleteandtable () {Getsqlparser (). skipifequal (Defaultkeyword.from); Getsqlparser (). skipifequal (oraclekeyword.only);}

3.2 #parseSingleTable ()

To parse the table , see the section "SQL Resolution (ii)" of SQL resolution #parseSingleTable() .

3.3 #parseWhere ()

Parses the WHERE condition. Parse code: SQL Resolution (ii) of SQL #parsewhere () section.

666. Eggs

Friend, can you share a wave with me?

Later SQL routing and rewriting will be more interesting yo!

SHARDING-JDBC Source analysis of database sub-Library sub-table middleware--sql parsing (vi) deleting SQL