如何使用Ruby DBI的'select_all'与'execute-fetch / each-finish'

问题描述

这是我使用DBI的示例代码：

Here is my sample code for using DBI:

dbh = DBI.connect("DBI:Mysql:host=#{server};database=mysql", user, pass)
rows = dbh.select_all("SHOW TABLES")

打印的行如下：

[["user"], ["user"], ["user"], ["user"], ["user"], ["user"], ["user"], ["user"],
 ["user"], ["user"], ["user"], ["user"], ["user"], ["user"], ["user"], ["user"],
 ["user"]]

这正在打印MySQL数据库中的最后一个表，但是记录总数是正确的。

This is printing the last table in a MySQL database, but the total number of records is proper.

如果我使用execute-fetch / each-finish序列执行此操作，则类似于：

If I do this using execute-fetch/each-finish sequence, something like:

sth = dbh.execute("SHOW TABLES")
sth.each do |row|
  rows << row[0]
end
sth.finish

这给了我适当的结果像这样：

It gives me proper results like:

["columns_priv", "db", "func", "help_category", "help_keyword", "help_relation",
 "help_topic", "host", "proc", "procs_priv", "tables_priv", "time_zone", "time_z
one_leap_second", "time_zone_name", "time_zone_transition", "time_zone_transitio
n_type", "user"]

推荐答案

相同当我使用 DBI.connect（ DBI：ODBC：Driver = {SQL Server}; ...）查询MS SQL DB时也会发生这种情况

我的解决方法是将DBI :: Row强制转换为数组：

My work around was to forcably convert the DBI::Row to an array:

sth = dbh.execute "..."
begin
  return sth.map{ |row| row.to_a }
ensure
  sth.finish
end

我打赌$ 1,000，问题出在缓冲区重用上-一种可能的性能增强，具有不良的副作用！

I'll bet $1,000 that the issue is to do with buffer reuse - a possible 'performance' enhancement that has had underirable side effects!

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