Cassandra and row cache
<p>I'd like to use row cache in Cassandra but I do not understand how it works.
I've enabled row cache in cassandra.yaml (2GB allocation) and changed the schema: </p>

<pre><code>ALTER TABLE d
with caching = {
    'keys' : 'ALL',
    'rows_per_partition' : '36000'
};
</code></pre>

<p>The key cache is working properly and I have an hit rate of 90%, while for row cache I see these numbers from <code>nodetool info</code>:</p>

<pre><code>Row Cache : entries 2, size 2 bytes, capacity 1.95 GB, 1620 hits, 39699640 requests, 0.000 recent hit rate, 0 save period in seconds
</code></pre>

<p>As you can see, cache contains only 2 entries, while I've performed 4M+ queries on all the entries on that table.</p>

<p>Any idea? What should I investigate to understand why the row cache is not used?</p>

<p><strong>UPDATE 1</strong>
Thanks to Chris, I've reconfigured cluster with row_cache_save_period = 14400. But I see no changes.</p>

<pre><code>Row Cache : entries 0, size 0 bytes, capacity 1.95 GB, 0 hits, 85098 requests, 0.000 recent hit rate, 14400 save period in seconds
</code></pre>

<p><strong>UPDATE 2</strong>
Here is schema definition:</p>

<pre><code>CREATE TABLE d_t (
    id bigint,
    xid bigint,
    ts timestamp,
    avg double,
    ce double,
    cg double,
    p double,
    w double,
    c double,
    sum double,
    last double,
    max double,
    min double,
    p75 double,
    p90 double,
    p95 double,
    squad double,
    sumq double,
    wavg double,
    weight double,
    PRIMARY KEY ((id), xid, ts)
) WITH CLUSTERING ORDER BY (xid DESC, ts DESC)
and  compaction = {'class': 'SizeTieredCompactionStrategy'} 
and gc_grace_seconds=86400
and caching = { 'keys' : 'ALL', 'rows_per_partition':'36000' }
and min_index_interval = 2
and max_index_interval = 20;
</code></pre>

<p><strong>UPDATE 3</strong></p>

<p>Using Cassandra 3.0.9</p>