maedhroz commented on code in PR #4150:
URL: https://github.com/apache/cassandra/pull/4150#discussion_r2085864979
##########
test/distributed/org/apache/cassandra/distributed/test/sai/StrictFilteringTest.java:
##########
@@ -216,6 +218,26 @@ public void testShortReadWithRegularColumns()
assertRows(initialRows, row(0, 1, 2));
}
+ @Test
+ public void testNoShortReadAtLimit()
+ {
+ CLUSTER.schemaChange(withKeyspace("CREATE TABLE %s.short_read_no_srp
(k int, c int, a int, PRIMARY KEY (k, c)) WITH read_repair = 'NONE'"));
+ CLUSTER.schemaChange(withKeyspace("CREATE INDEX ON
%s.short_read_no_srp(a) USING 'sai'"));
+ SAIUtil.waitForIndexQueryable(CLUSTER, KEYSPACE);
+
+ CLUSTER.get(1).executeInternal(withKeyspace("INSERT INTO
%s.short_read_no_srp(k, c, a) VALUES (0, 2, 1) USING TIMESTAMP 5"));
+ CLUSTER.get(2).executeInternal(withKeyspace("INSERT INTO
%s.short_read_no_srp(k, c, a) VALUES (0, 3, 1) USING TIMESTAMP 6"));
+
+ Long srpRequestsBefore = CLUSTER.get(1).callOnInstance(() ->
Keyspace.open(KEYSPACE).getColumnFamilyStore("short_read_no_srp").metric.shortReadProtectionRequests.getCount());
+
+ String select = withKeyspace("SELECT * FROM %s.short_read_no_srp WHERE
k = 0 AND a = 1 LIMIT 1");
+ Iterator<Object[]> initialRows =
CLUSTER.coordinator(1).executeWithPaging(select, ConsistencyLevel.ALL, 2);
+ assertRows(initialRows, row(0, 2, 1));
Review Comment:
Imagine a partition with 10,000 rows, 100 of which are matches for an index
or filtering query. With a limit of 10, the logic before this patch would have
to keep issuing SRP reads to find all 100 matches, which kills
performance...almost to a comical extent.
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