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From DuyHai Doan <doanduy...@gmail.com>
Subject Re: given partition key and secondary index, still require allow_filtering?
Date Mon, 31 Oct 2016 13:37:03 GMT
Native Cassandra 2nd index does not perform very well with inequalities (<,
>, <=, >=). In your case, even if you provide partition key (which is a
very good idea), Cassandra still need to perform a full scan on the local
node to find any score matching the inequality and it is pretty expensive,
thus requiring ALLOW FILTERING.

General thumb of rule for production is:  ALLOW FILTERING == SURELY TIMEOUT

On Mon, Oct 31, 2016 at 9:00 AM, Zao Liu <zaoliu@gmail.com> wrote:

> Hi,
>
> I created a table, schema like here:
>
> CREATE TABLE profile_new.user_categories_1477899735 (
>
>     id bigint,
>
>     category int,
>
>     score double,
>
>     PRIMARY KEY (id, category)
>
> ) WITH CLUSTERING ORDER BY (category ASC)
>
>     AND bloom_filter_fp_chance = 0.01
>
>     AND caching = {'keys': 'ALL', 'rows_per_partition': 'NONE'}
>
>     AND comment = ''
>
>     AND compaction = {'class': 'org.apache.cassandra.db.compaction.SizeTieredCompactionStrategy',
> 'max_threshold': '32', 'min_threshold': '4'}
>
>     AND compression = {'chunk_length_in_kb': '64', 'class': '
> org.apache.cassandra.io.compress.LZ4Compressor'}
>
>     AND crc_check_chance = 1.0
>
>     AND dclocal_read_repair_chance = 0.1
>
>     AND default_time_to_live = 0
>
>     AND gc_grace_seconds = 864000
>
>     AND max_index_interval = 2048
>
>     AND memtable_flush_period_in_ms = 0
>
>     AND min_index_interval = 128
>
>     AND read_repair_chance = 0.0
>
>     AND speculative_retry = '99PERCENTILE';
>
> CREATE INDEX user_categories_1477899735_score_idx ON
> profile_new.user_categories_1477899735 (score);
>
>
> cqlsh:profile_new> select * from user_categories_1477899735 where id=3674;
>
>
> But somehow when I pass partition key and secondary index key, it still
> complains:
>
> cqlsh:profile_new> select * from user_categories_1477899735 where id=3674
> and score > 0.5;
>
> *InvalidRequest: Error from server: code=2200 [Invalid query]
> message="Cannot execute this query as it might involve data filtering and
> thus may have unpredictable performance. If you want to execute this query
> despite the performance unpredictability, use ALLOW FILTERING"*
>
> cqlsh:profile_new>
>
>
>

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