On 02.11.2020 19:53, Matthias van de Meent wrote:
This is the result of network traffic of two backends one with enabled
compression and another with disable compression
after execution of "select * from pg_class" command:
select * from pg_stat_network_traffic;
pid | rx_raw_bytes | tx_raw_bytes | rx_compressed_bytes |
tx_compressed_bytes
-------+--------------+--------------+---------------------+---------------------
22276 | 29 | 86327 | 38
| 10656
22282 | 73 | 86327 | 0
| 0
The current names and values of these columns are confusing me:
What column contains the amount of bytes sent to/received from the
client? Is the compression method of pid 22282 extremely efficient at
compressing, or does it void the data (compresses down to 0 bytes)?
Names of the columns can be changed if you or somebody else will propose
better alternatives.
This view pg_stat_network_traffic reports traffic from server (backend)
point of view, i.e.
rx_bytes (received bytes) are commands sent from client to the server
tx_bytes (transmitted bytes) are responses sent by server to the client.
If compression is not used then rx_compressed_bytes =
tx_compressed_bytes = 0
It seems to be more natural then assigning them the same values as (raw
bytes).
Because it can really happen that for BLOBs with already compressed data
(video images or sound)
compressed data will be almost the same as raw data even if compression
is enabled.
So it seems to be important to distinguished situations when data can
not be compressed and
when it is not compressed at all.
I suggest having columns that contain the bytes sent to/received
from the client before and after compression. If no compression was
used, those numbers are expected to be equal. Example names are
`rx_raw_bytes` and `rx_data_bytes`, `rx_received_bytes` and
`rx_bytes_uncompressed`. Another option would be initializing /
setting rx_compressed_bytes and tx_compressed_bytes to -1 or NULL for
connections that do not utilize compression, to flag that
compression is not used.
-Matthias
