Ruby 错误：can't add a new key into hash during iteration (RuntimeError)
在用 SQLAnywhere 连接 Sybase IQ，有以下程序：
def db_query( dbh, sql )
sth = dbh.execute(sql)
print "# of Fields: #{sth.column_names.size}\n"
sth.fetch do |row|
print "\n"
sth.column_info.each_with_index do |info, i|
unless info["type_name"] == "LONG VARBINARY"
print "#{info["name"]}=#{row[i]}\n"
end
end
end
sth.finish
end
程序的完整地址：http://dcx.sap.com/sa160/fr/dbprogramming/pg-ruby-dbi.html 调用改程序进行查询，出现错误：
/home/sybase/.gem/ruby/gems/dbi-0.4.5/lib/dbi/columninfo.rb:49:in `[]=': can't add a new key into hash during iteration (RuntimeError)
from /home/sybase/.gem/ruby/gems/dbi-0.4.5/lib/dbi/columninfo.rb:49:in `block in initialize'
from /home/sybase/.gem/ruby/gems/dbi-0.4.5/lib/dbi/columninfo.rb:42:in `each_key'
from /home/sybase/.gem/ruby/gems/dbi-0.4.5/lib/dbi/columninfo.rb:42:in `initialize'
from /home/sybase/.gem/ruby/gems/dbi-0.4.5/lib/dbi/handles/statement.rb:185:in `new'
from /home/sybase/.gem/ruby/gems/dbi-0.4.5/lib/dbi/handles/statement.rb:185:in `block in column_info'
from /home/sybase/.gem/ruby/gems/dbi-0.4.5/lib/dbi/handles/statement.rb:185:in `collect'
from /home/sybase/.gem/ruby/gems/dbi-0.4.5/lib/dbi/handles/statement.rb:185:in `column_info'
from Conn2IQ3.rb:29:in `db_select'
from Conn2IQ3.rb:59:in `<main>'
这是什么原因？
终于查清楚原因了，是 dbi 包自身的问题，修改 dbi 的源代码如下: 源代码
@hash.each_key do |x|
if x.kind_of? String
sym = x.to_sym
if @hash.has_key? sym
raise ::TypeError,
"#{self.class.name} may construct from a hash keyed with strings or symbols, but not both"
end
@hash[sym] = @hash[x]
@hash.delete(x)
end
end
修改为如下：
hash_size = @hash.size()
keys = @hash.keys
#puts "#{keys}"
#puts hash_size
for i in 0..hash_size-1
keyi = keys[i]
#puts "#{keyi}"
if keys[i].kind_of? String
sym = keyi.to_sym
if @hash.has_key? sym
raise ::TypeError, "#{self.class.name} may construct from a hash keyed with strings or symbols, but not both"
end
@hash[sym] = @hash[keyi]
@hash.delete(keyi)
end
end
a = {a: 1, b: 2}
a.each { |k, v| a[v] = a[k] } # will raise "can't add a new key into hash during iteration"
a.dup.each { |k, v| a[v] = a[k] } # works
This error needs to be fixed immediately so that queries can continue to run smoothly. It is challenging to encounter such problem while working with iq test free!