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https://issues.apache.org/jira/browse/CASSANDRA-12915?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15871958#comment-15871958
]
Corentin Chary commented on CASSANDRA-12915:
--------------------------------------------
{code}
CREATE KEYSPACE test WITH replication = {'class': 'SimpleStrategy',
'replication_factor': '1'} AND durable_writes = true;
CREATE TABLE test.test (
r text PRIMARY KEY,
a text,
b text,
c text,
data text
);
CREATE CUSTOM INDEX test_a_idx ON test.test (a) USING
'org.apache.cassandra.index.sasi.SASIIndex' WITH OPTIONS = {'analyzer_class':
'org.apache.cassandra.index.sasi.analyzer.NonTokenizingAnalyzer',
'case_sensitive': 'true'};
CREATE CUSTOM INDEX test_c_idx ON test.test (c) USING
'org.apache.cassandra.index.sasi.SASIIndex' WITH OPTIONS = {'analyzer_class':
'org.apache.cassandra.index.sasi.analyzer.NonTokenizingAnalyzer',
'case_sensitive': 'true'};
CREATE CUSTOM INDEX test_b_idx ON test.test (b) USING
'org.apache.cassandra.index.sasi.SASIIndex' WITH OPTIONS = {'analyzer_class':
'org.apache.cassandra.index.sasi.analyzer.NonTokenizingAnalyzer',
'case_sensitive': 'true'};
{code}
{code}
$ cat > generate.py
import sys
import random
def main(args):
n = int(args[1])
for i in xrange(n):
a = '0'
b = i % 10
c = i % (n / 10) + random.randint(0, 10)
print ("%d,%s,%d,%d,%d" % (i, a, b, c, i))
if __name__ == '__main__':
main(sys.argv)
$ python generate.py 2000000 > test.csv
{code}
{code}
COPY test.test FROM 'test.csv' WITH MAXBATCHSIZE = 100 AND MAXATTEMPTS = 10
AND MAXINSERTERRORS = 999999;
{code}
{code}
cqlsh> SELECT * FROM test.test WHERE a = '1' AND c = '38151' LIMIT 1 ALLOW
FILTERING;
r | a | b | c | data
---+---+---+---+------
(0 rows)
Tracing session: fbc23200-f522-11e6-95df-69d39475f5a8
activity
|
timestamp | source | source_elapsed | client
-------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------+-----------+----------------+-----------
Execute CQL3 query |
2017-02-17 16:08:48.288000 | 127.0.0.1 | 0 | 127.0.0.1
Parsing SELECT * FROM test.test WHERE a = '1'
AND c = '38151' LIMIT 1 ALLOW FILTERING; [Native-Transport-Requests-1] |
2017-02-17 16:08:48.288000 | 127.0.0.1 | 268 | 127.0.0.1
Preparing statement [Native-Transport-Requests-1] |
2017-02-17 16:08:48.289000 | 127.0.0.1 | 513 | 127.0.0.1
Index mean cardinalities are
test_a_idx:-9223372036854775808,test_c_idx:-9223372036854775808. Scanning with
test_a_idx. [Native-Transport-Requests-1] | 2017-02-17 16:08:48.289000 |
127.0.0.1 | 913 | 127.0.0.1
Computing ranges to query [Native-Transport-Requests-1] |
2017-02-17 16:08:48.289000 | 127.0.0.1 | 1027 | 127.0.0.1
Submitting range requests on 257 ranges with a concurrency of 1
(-3.24259165E16 rows per range expected) [Native-Transport-Requests-1] |
2017-02-17 16:08:48.289001 | 127.0.0.1 | 1319 | 127.0.0.1
Submitted 1 concurrent range requests [Native-Transport-Requests-1] |
2017-02-17 16:08:48.290000 | 127.0.0.1 | 2229 | 127.0.0.1
Executing read on test.test using index test_a_idx [ReadStage-3] |
2017-02-17 16:08:48.292000 | 127.0.0.1 | 3494 | 127.0.0.1
Read 0 live and 0 tombstone cells [ReadStage-3] |
2017-02-17 16:08:48.293000 | 127.0.0.1 | 4694 | 127.0.0.1
Request complete |
2017-02-17 16:08:48.292930 | 127.0.0.1 | 4930 | 127.0.0.1
{code}
Yay ! No more iterating on the useless index.
Patch is on https://github.com/iksaif/cassandra/tree/sasi-null-intersect
> SASI: Index intersection with an empty range really inefficient
> ---------------------------------------------------------------
>
> Key: CASSANDRA-12915
> URL: https://issues.apache.org/jira/browse/CASSANDRA-12915
> Project: Cassandra
> Issue Type: Improvement
> Components: sasi
> Reporter: Corentin Chary
> Assignee: Corentin Chary
> Fix For: 3.11.x, 4.x
>
>
> It looks like RangeIntersectionIterator.java and be pretty inefficient in
> some cases. Let's take the following query:
> SELECT data FROM table WHERE index1 = 'foo' AND index2 = 'bar';
> In this case:
> * index1 = 'foo' will match 2 items
> * index2 = 'bar' will match ~300k items
> On my setup, the query will take ~1 sec, most of the time being spent in
> disk.TokenTree.getTokenAt().
> if I patch RangeIntersectionIterator so that it doesn't try to do the
> intersection (and effectively only use 'index1') the query will run in a few
> tenth of milliseconds.
> I see multiple solutions for that:
> * Add a static thresold to avoid the use of the index for the intersection
> when we know it will be slow. Probably when the range size factor is very
> small and the range size is big.
> * CASSANDRA-10765
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