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|
# -*- ruby -*-
require 'pg'
$stdout.sync = true
# This is a example of how to mix and match synchronous and async APIs. In this case,
# the connection to the server is made syncrhonously, and then queries are
# asynchronous.
TIMEOUT = 5.0 # seconds to wait for an async operation to complete
CONN_OPTS = {
:host => 'localhost',
:dbname => 'test',
}
# Output progress messages
def output_progress( msg )
puts ">>> #{msg}\n"
end
# Start the (synchronous) connection
output_progress "Starting connection..."
conn = PG.connect( CONN_OPTS ) or abort "Unable to create a new connection!"
abort "Connect failed: %s" % [ conn.error_message ] unless conn.status == PG::CONNECTION_OK
# Now grab a reference to the underlying socket to select() on while the query is running
socket = conn.socket_io
# Send the (asynchronous) query
output_progress "Sending query"
conn.send_query( "SELECT * FROM pg_stat_activity" )
# Fetch results until there aren't any more
loop do
output_progress " waiting for a response"
# Buffer any incoming data on the socket until a full result is ready.
conn.consume_input
while conn.is_busy
output_progress " waiting for data to be available on %p..." % [ socket ]
select( [socket], nil, nil, TIMEOUT ) or
raise "Timeout waiting for query response."
conn.consume_input
end
# Fetch the next result. If there isn't one, the query is finished
result = conn.get_result or break
output_progress "Query result:\n%p\n" % [ result.values ]
end
output_progress "Done."
conn.finish
|
