CODEWITHSUNDEEP
rubypostgresqlactiverecordpsqlpg
tk_0709
tk_0709

Reputation: 21

ruby raised another command is already in progress

I would like to enter a large amount of data in my file. To do this, I am thinking of using postgresql's asynchronous processing to do the query. The code is as follows.

raw_conn = ActiveRecord::Base.connection.raw_connection

raw_conn.send_query("SELECT id FROM users")
raw_conn.set_single_row_mode
begin
  raw_conn.get_result.stream_each do |f|
    # writing process to file
  end
end

raw_conn.send_query("SELECT id FROM logins")
raw_conn.set_single_row_mode
begin
  raw_conn.get_result.stream_each do |f|
    # writing process to file
  end
end

When the second send_query is executed, the following error occurs.

 another command is already in progress

I had a feeling that the connection pool was the cause, but the documentation did not mention it. Is there any way to run send_query more than once and get results?

Upvotes: 0

Views: 151

Answers (2)

Michael Reinsch
Michael Reinsch

Reputation: 579

The reset didn't quite work for me (pg 1.5.6), but I found the method discard_results which seems to resolve this for me. I'm not quite positive why the command is still ongoing and whether there is an official way to handle this?

Anyway, my solution for now looks something like this:

begin
  raw_connection = ActiveRecord::Base.connection.raw_connection
  raw_connection.send_query(sql)
  raw_connection.set_single_row_mode
  db_result = raw_connection.get_result
  db_result.stream_each do |row|
     # handle row
  end
ensure
  # added because of exception: "another command is already in progress"
  raw_connection.discard_results
end

Upvotes: 0

tk_0709
tk_0709

Reputation: 21

I Resolved. I tried to reset the connection before sending a new query, and it worked.

begin
  raw_conn.get_result.stream_each do |f|
    # writing process to file
  end
ensure
 raw_conn.reset
end

Upvotes: 1

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