gudusoft.gsqlparser.resolver

Class TStarColumnPushDownResolver

Object

gudusoft.gsqlparser.nodes.TParseTreeVisitor

gudusoft.gsqlparser.resolver.TStarColumnPushDownResolver

public class TStarColumnPushDownResolver
extends TParseTreeVisitor

TStarColumnPushDownResolver 类负责解析和处理 SQL 查询中的星号(*)列引用， 将星号列引用追溯到实际的表列。 主要工作流程： 1. 从顶层查询开始，向下遍历所有子查询 2. 对每个查询中的星号列，找到其对应的实际列 3. 将这些列信息传递给下层查询 4. 最终将星号列解析到实际的表列 关键依赖类： - TContext: 提供全局作用域信息 - TScope: 管理查询作用域 - TSelectSqlStatement: 表示 SELECT 语句 - TTable: 表示表引用 - TResultColumn: 表示结果列 - TObjectName: 表示对象名称 - TAttributeNode: 表示属性节点

Constructor Summary

Constructors

Constructor and Description
TStarColumnPushDownResolver(TStatementList sqls, gudusoft.gsqlparser.compiler.TContext scope) 构造函数

Method Summary

Modifier and Type	Method and Description
void	postVisit(TSelectSqlStatement stmt) 处理 CTE (Common Table Expression) 中的星号列 工作流程： 1.
void	preVisit(TSelectSqlStatement stmt) 处理 SELECT 语句中的星号列 工作流程： 1.
void	resolve() 开始解析过程 遍历所有 SQL 语句，对每个语句执行星号列下推解析

Methods inherited from class gudusoft.gsqlparser.nodes.TParseTreeVisitor

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Methods inherited from class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

TStarColumnPushDownResolver

public TStarColumnPushDownResolver(TStatementList sqls,
                                   gudusoft.gsqlparser.compiler.TContext scope)

构造函数

Parameters:

sqls - SQL语句列表

scope - 全局作用域

Method Detail

resolve

public void resolve()

开始解析过程 遍历所有 SQL 语句，对每个语句执行星号列下推解析

preVisit

public void preVisit(TSelectSqlStatement stmt)

处理 SELECT 语句中的星号列 工作流程： 1. 检查是否已处理过该语句 2. 处理 UNION 等集合操作的情况 3. 遍历结果列表中的星号列 4. 对每个星号列： - 检查是否有精确匹配的列 - 处理多个表的星号情况 - 根据表类型（实体表/子查询）进行相应处理

Overrides:

preVisit in class TParseTreeVisitor

Parameters:

stmt - SELECT 语句对象 示例： SELECT col_1, col_11, col_2 FROM ( select * FROM (select * from table_a) ta ) a LEFT OUTER JOIN ( select id, col_2 FROM table_b ) b on a.id = b.id

postVisit

public void postVisit(TSelectSqlStatement stmt)

处理 CTE (Common Table Expression) 中的星号列 工作流程： 1. 检查是否存在 CTE 2. 从后向前遍历 CTE 列表 3. 对每个 CTE： - 处理其子查询中的星号列 - 特别处理 UNION 等集合操作的情况

Overrides:

postVisit in class TParseTreeVisitor

Parameters:

stmt - SELECT 语句对象