Editing TimeScale Notes (section)

== Compression ==

=== Check Distinct Values ===
<pre>
-- n_distinct (-1 = Unique, 1 = All The Same)
SELECT tablename, attname, most_common_vals, most_common_freqs, n_distinct 
FROM pg_stats 
-- WHERE tablename = '<TableName>'; 
WHERE schemaname = '<SchemaName>'; 
</pre>

=== Compress Table ===
<pre>
ALTER TABLE crypto_ticks
SET (timescaledb.compress,
     timescaledb.compress_segmentby='symbol',
     timescaledb.compress_orderby='time DESC');
</pre>

<code>SELECT compress_chunk(c) from show_chunks('crypto_ticks') c; </code>

=== Check Compression ===
<pre>
SELECT pg_size_pretty(before_compression_total_bytes) as before, 
       pg_size_pretty(after_compression_total_bytes) as after 
  FROM hypertable_compression_stats('crypto_ticks'); 

SELECT pg_size_pretty(hypertable_size('CRYPTO_TICKS'));
</pre>

=== Compression Policy ===
Create a scheduled job that will compress all data with a 'time' column that is older than 8 days. </br>
<pre>SELECT add_compression_policy('crypto_ticks', INTERVAL '8 days'); </pre>

=== Links ===
https://docs.timescale.com/tutorials/latest/financial-tick-data/financial-tick-compress

Since version 2.18, HyperCore has been used for compression. </br>
This uses a hybrid of row and columnar storage. </br>
https://docs.timescale.com/use-timescale/latest/compression (Old) </br>
https://docs.timescale.com/use-timescale/latest/hypercore]  (New)