What if i use sstabledump? Because i'm going to read all data from a table that has no more insert/compaction(fixed list of sstables).
For each sstable: 1. Using sstabledump -e, fetch all partition keys stored on sstable (ordered list) 2. Using sstabledump -k partitionKey, fetch all rows for the partitionKey on the sstable, by nodetool getsstables, check if there is any other part of data on other sstables This way maybe i could get 100% disk read performance (fast possible sequential read of all data on a table) I will put the outcome of this experiment here Sent using https://www.zoho.com/mail/ ============ Forwarded message ============ From: onmstester onmstester <onmstes...@zoho.com.INVALID> To: "user"<user@cassandra.apache.org> Date: Sat, 14 Nov 2020 08:24:14 +0330 Subject: Re: local read from coordinator ============ Forwarded message ============ Thank you Jeff, I disabled dynamic_snitch (after reading some Docs about how its not working good enough in production) and using GossipingFileProperty snitch, Is it make any difference to choosing the replica? Sent using https://www.zoho.com/mail/ ---- On Wed, 11 Nov 2020 17:53:42 +0330 Jeff Jirsa <mailto:jji...@gmail.com> wrote ---- This isn’t necessarily true and cassandra has no coordinator-only consistency level to force this behavior (The snitch is going to pick the best option for local_one reads and any compactions or latency deviations from load will make it likely that another replica is chosen in practice) On Nov 11, 2020, at 3:46 AM, Alex Ott <mailto:alex...@gmail.com> wrote: if you force routing key, then the replica that owns the data will be selected as coordinator On Wed, Nov 11, 2020 at 12:35 PM onmstester onmstester <mailto:onmstes...@zoho.com.invalid> wrote: Thanx, But i'm OK with coordinator part, actually i was looking for kind of read CL to force to read from the coordinator only with no other connections to other nodes! Sent using https://www.zoho.com/mail/ ============ Forwarded message ============ From: Alex Ott <mailto:alex...@gmail.com> To: "user"<mailto:user@cassandra.apache.org> Date: Wed, 11 Nov 2020 11:28:56 +0330 Subject: Re: local read from coordinator ============ Forwarded message ============ token-aware policy doesn't work for token range queries (at least in the Java driver 3.x). You need to force the driver to do the reading using a specific token as a routing key. Here is Java implementation of the token range scanning algorithm that Spark uses: https://github.com/alexott/cassandra-dse-playground/blob/master/driver-1.x/src/main/java/com/datastax/alexott/demos/TokenRangesScan.java I'm not aware if Python driver is able to set routing key explicitly, but whitelist policy should help On Wed, Nov 11, 2020 at 7:03 AM Erick Ramirez <mailto:erick.rami...@datastax.com> wrote: Yes, use a token-aware policy so the driver will pick a coordinator where the token (partition) exists. Cheers! -- With best wishes, Alex Ott http://alexott.net/ Twitter: alexott_en (English), alexott (Russian) -- With best wishes, Alex Ott http://alexott.net/ Twitter: alexott_en (English), alexott (Russian)
