com.alibaba.druid.sql.ast.statement.SQLDeleteStatement Java Examples

/**
 * Create the compatible Query object
 * based on the SQL query.
 * @param sql The SQL query.
 * @return Query object.
 */
   public static QueryAction create(Client client, String sql) throws SqlParseException, SQLFeatureNotSupportedException {
       sql = sql.replaceAll("\n", " ").trim();
       String firstWord = sql.substring(0, sql.indexOf(' '));
       switch (firstWord.toUpperCase()) {
		case "SELECT":
		    //zhongshu-comment 将sql字符串解析成AST，即SQLQueryExpr sqlExpr就是AST了，下面的代码就开始访问AST、从中获取token
			SQLQueryExpr sqlExpr = (SQLQueryExpr) toSqlExpr(sql);
               if(isMulti(sqlExpr)){//zhongshu-comment 判断是不是union查询，union查询两个select语句，btw：子查询也有多个select语句，至少2个
                   MultiQuerySelect multiSelect = new SqlParser().parseMultiSelect((SQLUnionQuery) sqlExpr.getSubQuery().getQuery());
                   handleSubQueries(client,multiSelect.getFirstSelect());
                   handleSubQueries(client,multiSelect.getSecondSelect());
                   return new MultiQueryAction(client, multiSelect);
               }
               else if(isJoin(sqlExpr,sql)){//zhongshu-comment join连接查询
                   JoinSelect joinSelect = new SqlParser().parseJoinSelect(sqlExpr);
                   handleSubQueries(client, joinSelect.getFirstTable());
                   handleSubQueries(client, joinSelect.getSecondTable());
                   return ESJoinQueryActionFactory.createJoinAction(client, joinSelect);
               }
               else {
                   //zhongshu-comment 大部分查询都是走这个分支，先看懂这个分支
                   Select select = new SqlParser().parseSelect(sqlExpr);
                   //todo 看不懂，测试了好几个常见的sql，都没有进去handleSubQueries该方法，那就先不理了，看别的
                   handleSubQueries(client, select);
                   return handleSelect(client, select);
               }
		case "DELETE":
               SQLStatementParser parser = createSqlStatementParser(sql);
			SQLDeleteStatement deleteStatement = parser.parseDeleteStatement();
			Delete delete = new SqlParser().parseDelete(deleteStatement);
			return new DeleteQueryAction(client, delete);
           case "SHOW":
               return new ShowQueryAction(client,sql);
		default:
			throw new SQLFeatureNotSupportedException(String.format("Unsupported query: %s", sql));
	}
}
 

/**
     * 从between语句中获取字段所属的表名。
     * 对于容易出现ambiguous的（字段不知道到底属于哪个表），实际应用中必须使用别名来避免歧义
     * @param betweenExpr
     * @param column
     * @return
     */
    private String getOwnerTableName(SQLBetweenExpr betweenExpr,String column) {
        if(tableStats.size() == 1) {//只有一个表，直接返回这一个表名
            return tableStats.keySet().iterator().next().getName();
        } else if(tableStats.size() == 0) {//一个表都没有，返回空串
            return "";
        } else {//多个表名
            for (Column col : columns.keySet())
            {
                if(col.getName().equals(column)) {
                    return col.getTable();
                }
            }
//            for(Column col : columns) {//从columns中找表名
//                if(col.getName().equals(column)) {
//                    return col.getTable();
//                }
//            }

            //前面没找到表名的，自己从parent中解析

            SQLObject parent = betweenExpr.getParent();
            if(parent instanceof SQLBinaryOpExpr)
            {
                parent=parent.getParent();
            }

            if(parent instanceof MySqlSelectQueryBlock) {
                MySqlSelectQueryBlock select = (MySqlSelectQueryBlock) parent;
                if(select.getFrom() instanceof SQLJoinTableSource) {//多表连接
                    SQLJoinTableSource joinTableSource = (SQLJoinTableSource)select.getFrom();
                    return joinTableSource.getLeft().toString();//将left作为主表，此处有不严谨处，但也是实在没有办法，如果要准确，字段前带表名或者表的别名即可
                } else if(select.getFrom() instanceof SQLExprTableSource) {//单表
                    return select.getFrom().toString();
                }
            }
            else if(parent instanceof SQLUpdateStatement) {
                SQLUpdateStatement update = (SQLUpdateStatement) parent;
                return update.getTableName().getSimpleName();
            } else if(parent instanceof SQLDeleteStatement) {
                SQLDeleteStatement delete = (SQLDeleteStatement) parent;
                return delete.getTableName().getSimpleName();
            } else {
                
            }
        }
        return "";
    }
 

public WhereParser(SqlParser sqlParser, SQLDeleteStatement delete) {
    this.sqlParser = sqlParser;
    this.delete = delete;
    this.where = delete.getWhere();
}
 

public Delete parseDelete(SQLDeleteStatement deleteStatement) throws SqlParseException {
    Delete delete = new Delete();
    WhereParser whereParser = new WhereParser(this, deleteStatement);

    delete.getFrom().addAll(findFrom(deleteStatement.getTableSource()));

    delete.setWhere(whereParser.findWhere());

    delete.getHints().addAll(parseHints(((MySqlDeleteStatement) deleteStatement).getHints()));

    findLimit(((MySqlDeleteStatement) deleteStatement).getLimit(), delete);

    return delete;
}