When iterating over rows in a postgres DB using 'use_cursor', the
underlying 'cursor_fetch_rows' always names the cursor 'sequel_cursor'.
This means that use_cursor calls cannot be embedded within each other
(say, for doing joins in memory). Is it possible to have an optimal
:cursor_name argument passed to 'use_cursor' to prevent this?
I would change the following in adapters/postgres.rb
def use_cursor(opts=OPTS)
clone(:cursor=>{:rows_per_fetch=>1000,
:cursor_name=>"sequel_cursor"}.merge(opts))
end
def cursor_fetch_rows(sql)
server_opts = {:server=>@opts[:server] || :read_only}
db.transaction(server_opts) do
begin
cursor_name = @opts[:cursor][:cursor_name]
execute_ddl("DECLARE #{cursor_name} NO SCROLL CURSOR WITHOUT
HOLD FOR #{sql}", server_opts)
rows_per_fetch = @opts[:cursor][:rows_per_fetch].to_i
rows_per_fetch = 1000 if rows_per_fetch <= 0
fetch_sql = "FETCH FORWARD #{rows_per_fetch} FROM
#{cursor_name}"
cols = nil
# Load columns only in the first fetch, so subsequent fetches are faster
execute(fetch_sql) do |res|
cols = fetch_rows_set_cols(res)
yield_hash_rows(res, cols){|h| yield h}
return if res.ntuples < rows_per_fetch
end
loop do
execute(fetch_sql) do |res|
yield_hash_rows(res, cols){|h| yield h}
return if res.ntuples < rows_per_fetch
end
end
ensure
execute_ddl("CLOSE #{cursor_name}", server_opts)
end
end
end
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