clickhouse secondary index
Secondary indexes: yes, when using the MergeTree engine: yes: yes; SQL Support of SQL: Close to ANSI SQL: yes: ANSI-99 for query and DML statements, subset of DDL; Ultimately, I recommend you try the data skipping index yourself to improve the performance of your Clickhouse queries, especially since its relatively cheap to put in place. Clickhouse MergeTree table engine provides a few data skipping indexes which makes queries faster by skipping granules of data (A granule is the smallest indivisible data set that ClickHouse reads when selecting data) and therefore reducing the amount of data to read from disk. If you create an index for the ID column, the index file may be large in size. Find centralized, trusted content and collaborate around the technologies you use most. 8028160 rows with 10 streams. The following is illustrating how the ClickHouse generic exclusion search algorithm works when granules are selected via a secondary column where the predecessor key column has a low(er) or high(er) cardinality. ), 31.67 MB (306.90 million rows/s., 1.23 GB/s. column are scanned: Normally skip indexes are only applied on newly inserted data, so just adding the index won't affect the above query. Is it safe to talk about ideas that have not patented yet over public email. These structures are labeled "Skip" indexes because they enable ClickHouse to skip reading significant chunks of data that are guaranteed to have no matching values. ngrambf_v1 and tokenbf_v1 are two interesting indexes using bloom Executor): Key condition: (column 0 in ['http://public_search', Executor): Running binary search on index range for part all_1_9_2 (1083 marks), Executor): Found (LEFT) boundary mark: 644, Executor): Found (RIGHT) boundary mark: 683, Executor): Found continuous range in 19 steps, 39/1083 marks by primary key, 39 marks to read from 1 ranges, Executor): Reading approx. As a consequence, if we want to significantly speed up our sample query that filters for rows with a specific URL then we need to use a primary index optimized to that query. On the other hand if you need to load about 5% of data, spread randomly in 8000-row granules (blocks) then probably you would need to scan almost all the granules. After failing over from Primary to Secondary, . Why did the Soviets not shoot down US spy satellites during the Cold War? In contrast, minmax indexes work particularly well with ranges since determining whether ranges intersect is very fast. But once we understand how they work and which one is more adapted to our data and use case, we can easily apply it to many other columns. You can create an index for the, The ID column in a secondary index consists of universally unique identifiers (UUIDs). Index manipulation is supported only for tables with *MergeTree engine (including replicated variants). example, all of the events for a particular site_id could be grouped and inserted together by the ingest process, even if the primary key Certain error codes, while rare in the data, might be particularly Also, they are replicated, syncing indices metadata via ZooKeeper. In contrast to the diagram above, the diagram below sketches the on-disk order of rows for a primary key where the key columns are ordered by cardinality in descending order: Now the table's rows are first ordered by their ch value, and rows that have the same ch value are ordered by their cl value. ClickHouse has a lot of differences from traditional OLTP (online transaction processing) databases like PostgreSQL. Examples SHOW INDEXES ON productsales.product; System Response For further information, please visit instana.com. 2 comments Slach commented on Jul 12, 2019 cyriltovena added the kind/question label on Jul 15, 2019 Slach completed on Jul 15, 2019 Sign up for free to join this conversation on GitHub . It only takes a bit more disk space depending on the configuration and it could speed up the query by 4-5 times depending on the amount of data that can be skipped. a query that is searching for rows with URL value = "W3". The core purpose of data-skipping indexes is to limit the amount of data analyzed by popular queries. Index name. Secondary indexes in ApsaraDB for ClickHouse, Multi-column indexes and expression indexes, High compression ratio that indicates a similar performance to Lucene 8.7 for index file compression, Vectorized indexing that is four times faster than Lucene 8.7, You can use search conditions to filter the time column in a secondary index on an hourly basis. When a query is filtering on both the first key column and on any key column(s) after the first then ClickHouse is running binary search over the first key column's index marks. We decided to set the index granularity to 4 to get the index lookup time down to within a second on our dataset. Asking for help, clarification, or responding to other answers. ClickHouseClickHouse This type of index only works correctly with a scalar or tuple expression -- the index will never be applied to expressions that return an array or map data type. We also need to estimate the number of tokens in each granule of data. 319488 rows with 2 streams, URLCount, http://auto.ru/chatay-barana.. 170 , http://auto.ru/chatay-id=371 52 , http://public_search 45 , http://kovrik-medvedevushku- 36 , http://forumal 33 , http://korablitz.ru/L_1OFFER 14 , http://auto.ru/chatay-id=371 14 , http://auto.ru/chatay-john-D 13 , http://auto.ru/chatay-john-D 10 , http://wot/html?page/23600_m 9 , , 73.04 MB (340.26 million rows/s., 3.10 GB/s. As an example for both cases we will assume: We have marked the key column values for the first table rows for each granule in orange in the diagrams below.. An Adaptive Radix Tree (ART) is mainly used to ensure primary key constraints and to speed up point and very highly selective (i.e., < 0.1%) queries. command. ClickHouse Meetup in Madrid New Features of ClickHouse Secondary Indices. The following table describes the test results. The ngrams of each column value will be stored in the bloom filter. And because of that is is also unlikely that cl values are ordered (locally - for rows with the same ch value). let's imagine that you filter for salary >200000 but 99.9% salaries are lower than 200000 - then skip index tells you that e.g. min-max indexes) are currently created using CREATE TABLE users (uid Int16, name String, age Int16, INDEX bf_idx(name) TYPE minmax GRANULARITY 2) ENGINE=M. In this case, you can use a prefix function to extract parts of a UUID to create an index. Now that weve looked at how to use Clickhouse data skipping index to optimize query filtering on a simple String tag with high cardinality, lets examine how to optimize filtering on HTTP header, which is a more advanced tag consisting of both a key and a value. Oracle certified MySQL DBA. If in addition we want to keep the good performance of our sample query that filters for rows with a specific UserID then we need to use multiple primary indexes. As soon as that range reaches 512 MiB in size, it splits into . The bloom_filter index and its 2 variants ngrambf_v1 and tokenbf_v1 all have some limitations. The number of blocks that can be skipped depends on how frequently the searched data occurs and how its distributed in the table. ), 0 rows in set. Even when a data skipping index is appropriate, careful tuning both the index and the table Skip indexes (clickhouse secondary indexes) help if you have some rare values in your query or extra structure in data (correlation to index). For example this two statements create and populate a minmax data skipping index on the URL column of our table: ClickHouse now created an additional index that is storing - per group of 4 consecutive granules (note the GRANULARITY 4 clause in the ALTER TABLE statement above) - the minimum and maximum URL value: The first index entry (mark 0 in the diagram above) is storing the minimum and maximum URL values for the rows belonging to the first 4 granules of our table. https://clickhouse.tech/docs/en/engines/table-engines/mergetree-family/mergetree/#table_engine-mergetree-data_skipping-indexes, The open-source game engine youve been waiting for: Godot (Ep. Connect and share knowledge within a single location that is structured and easy to search. Accordingly, selecting a primary key that applies to the most common query patterns is essential for effective table design. each granule contains two rows. However, this type of secondary index will not work for ClickHouse (or other column-oriented databases) because there are no individual rows on the disk to add to the index. the index in mrk is primary_index*3 (each primary_index has three info in mrk file). Click "Add Schema" and enter the dimension, metrics and timestamp fields (see below) and save it. Increasing the granularity would make the index lookup faster, but more data might need to be read because fewer blocks will be skipped. One example SHOW SECONDARY INDEXES Function This command is used to list all secondary index tables in the CarbonData table. If each block contains a large number of unique values, either evaluating the query condition against a large index set will be very expensive, or the index will not be applied because the index is empty due to exceeding max_size. Predecessor key column has low(er) cardinality. This index type is usually the least expensive to apply during query processing. When creating a second table with a different primary key then queries must be explicitly send to the table version best suited for the query, and new data must be inserted explicitly into both tables in order to keep the tables in sync: With a materialized view the additional table is implicitly created and data is automatically kept in sync between both tables: And the projection is the most transparent option because next to automatically keeping the implicitly created (and hidden) additional table in sync with data changes, ClickHouse will automatically choose the most effective table version for queries: In the following we discuss this three options for creating and using multiple primary indexes in more detail and with real examples. And vice versa: Because Bloom filters can more efficiently handle testing for a large number of discrete values, they can be appropriate for conditional expressions that produce more values to test. Nevertheless, no matter how carefully tuned the primary key, there will inevitably be query use cases that can not efficiently use it. ]table_name (col_name1, col_name2) AS 'carbondata ' PROPERTIES ('table_blocksize'='256'); Parameter Description Precautions db_name is optional. After the index is added, only new incoming data will get indexed. In order to illustrate that, we give some details about how the generic exclusion search works. let's imagine that you filter for salary >200000 but 99.9% salaries are lower than 200000 - then skip index tells you that e.g. Key is a Simple Scalar Value n1ql View Copy In the above example, searching for `hel` will not trigger the index. We can add indexes to both the key and the value column. The final index creation statement looks something like this: ADD INDEX IF NOT EXISTS tokenbf_http_url_index lowerUTF8(http_url) TYPE tokenbf_v1(10240, 3, 0) GRANULARITY 4. The secondary indexes have the following features: Multi-column indexes are provided to help reduce index merges in a specific query pattern. Alibaba Cloud ClickHouse provides an exclusive secondary index capability to strengthen the weakness. PSsysbenchcli. I have the following code script to define a MergeTree Table, and the table has a billion rows. Instead of reading all 32678 rows to find The cost, performance, and effectiveness of this index is dependent on the cardinality within blocks. Critically, if a value occurs even once in an indexed block, it means the entire block must be read into memory and evaluated, and the index cost has been needlessly incurred. ClickHouse is a registered trademark of ClickHouse, Inc. 799.69 MB (102.11 million rows/s., 9.27 GB/s.). In common scenarios, a wide table that records user attributes and a table that records user behaviors are used. 15 comments healiseu commented on Oct 6, 2018 Dictionaries CAN NOT be reloaded in RAM from source tables on the disk The uncompressed data size is 8.87 million events and about 700 MB. It supports the conditional INTERSET, EXCEPT, and UNION search of multiple index columns. Instana also gives visibility into development pipelines to help enable closed-loop DevOps automation. Instana, an IBM company, provides an Enterprise Observability Platform with automated application monitoring capabilities to businesses operating complex, modern, cloud-native applications no matter where they reside on-premises or in public and private clouds, including mobile devices or IBM Z. To search for specific users, you must aggregate and filter out the user IDs that meet specific conditions from the behavior table, and then use user IDs to retrieve detailed records from the attribute table. ALTER TABLE [db. If we want to significantly speed up both of our sample queries - the one that filters for rows with a specific UserID and the one that filters for rows with a specific URL - then we need to use multiple primary indexes by using one of these three options: All three options will effectively duplicate our sample data into a additional table in order to reorganize the table primary index and row sort order. A traditional secondary index would be very advantageous with this kind of data distribution. Source/Destination Interface SNMP Index does not display due to App Server inserting the name in front. Open-source ClickHouse does not have secondary index capabilities. However, this type of secondary index will not work for ClickHouse (or other column-oriented databases) because there are no individual rows on the disk to add to the index. Instead it has to assume that granule 0 potentially contains rows with URL value W3 and is forced to select mark 0. At Instana, we process and store every single call collected by Instana tracers with no sampling over the last 7 days. Active MySQL Blogger. 'http://public_search') very likely is between the minimum and maximum value stored by the index for each group of granules resulting in ClickHouse being forced to select the group of granules (because they might contain row(s) matching the query). From a SQL perspective, a table and its secondary indexes initially map to a single range, where each key-value pair in the range represents a single row in the table (also called the primary index because the table is sorted by the primary key) or a single row in a secondary index. a granule size of two i.e. If not, pull it back or adjust the configuration. tokenbf_v1 splits the string into tokens separated by non-alphanumeric characters and stores tokens in the bloom filter. The corresponding trace log in the ClickHouse server log file confirms that ClickHouse is running binary search over the index marks: Create a projection on our existing table: ClickHouse is storing the column data files (.bin), the mark files (.mrk2) and the primary index (primary.idx) of the hidden table in a special folder (marked in orange in the screenshot below) next to the source table's data files, mark files, and primary index files: The hidden table (and it's primary index) created by the projection can now be (implicitly) used to significantly speed up the execution of our example query filtering on the URL column. ALTER TABLE [db].table_name [ON CLUSTER cluster] ADD INDEX name expression TYPE type GRANULARITY value [FIRST|AFTER name] - Adds index description to tables metadata. The basic question I would ask here is whether I could think the Clickhouse secondary index as MySQL normal index. Does Cosmic Background radiation transmit heat? Established system for high-performance time-series lookups using Scylla and AWS, with rapid deployments, custom on-node metrics exporters, and data . above example, the debug log shows that the skip index dropped all but two granules: This lightweight index type requires no parameters. Here, the author added a point query scenario of secondary indexes to test . In our case, the number of tokens corresponds to the number of distinct path segments. Unlike other database management systems, secondary indexes in ClickHouse do not point to specific rows or row ranges. and are available only in ApsaraDB for ClickHouse 20.3 and 20.8. TYPE. Elapsed: 0.024 sec.Processed 8.02 million rows,73.04 MB (340.26 million rows/s., 3.10 GB/s. With URL as the first column in the primary index, ClickHouse is now running binary search over the index marks. This can not be excluded because the directly succeeding index mark 1 does not have the same UserID value as the current mark 0. for each block (if the expression is a tuple, it separately stores the values for each member of the element We also hope Clickhouse continuously improves these indexes and provides means to get more insights into their efficiency, for example by adding index lookup time and the number granules dropped in the query log. However, the potential for false positives does mean that the indexed expression should be expected to be true, otherwise valid data may be skipped. The following statement provides an example on how to specify secondary indexes when you create a table: The following DDL statements provide examples on how to manage secondary indexes: Secondary indexes in ApsaraDB for ClickHouse support the basic set operations of intersection, union, and difference on multi-index columns. The input expression is split into character sequences separated by non-alphanumeric characters. In ClickHouse, we can add another class of indexes called data skipping indexes, which uses . In the following we illustrate why it's beneficial for the compression ratio of a table's columns to order the primary key columns by cardinality in ascending order. E.g. rev2023.3.1.43269. The ClickHouse team has put together a really great tool for performance comparisons, and its popularity is well-deserved, but there are some things users should know before they start using ClickBench in their evaluation process. In addition to the limitation of not supporting negative operators, the searched string must contain at least a complete token. Compared with the multi-dimensional search capability of Elasticsearch, the secondary index feature is easy to use. Many factors affect ClickHouse query performance. This can happen either when: Each type of skip index works on a subset of available ClickHouse functions appropriate to the index implementation listed Accordingly, skip indexes must interact correctly with common functions to be efficient. of the tuple). ClickHouse is storing the column data files (.bin), the mark files (.mrk2) and the primary index (primary.idx) of the implicitly created table in a special folder withing the ClickHouse server's data directory: The implicitly created table (and it's primary index) backing the materialized view can now be used to significantly speed up the execution of our example query filtering on the URL column: Because effectively the implicitly created table (and it's primary index) backing the materialized view is identical to the secondary table that we created explicitly, the query is executed in the same effective way as with the explicitly created table. Clickhouse provides ALTER TABLE [db. Reducing the false positive rate will increase the bloom filter size. include variations of the type, granularity size and other parameters. We will use a subset of 8.87 million rows (events) from the sample data set. But because the first key column ch has high cardinality, it is unlikely that there are rows with the same ch value. Functions with a constant argument that is less than ngram size cant be used by ngrambf_v1 for query optimization. )Server Log:Executor): Key condition: (column 1 in [749927693, 749927693])Executor): Used generic exclusion search over index for part all_1_9_2 with 1453 stepsExecutor): Selected 1/1 parts by partition key, 1 parts by primary key, 980/1083 marks by primary key, 980 marks to read from 23 rangesExecutor): Reading approx. A false positive is not a significant concern in the case of skip indexes because the only disadvantage is reading a few unnecessary blocks. Handling multi client projects round the clock. This command is used to create secondary indexes in the CarbonData tables. ClickHouse was created 10 years ago and is already used by firms like Uber, eBay,. For example, if the granularity of the primary table index is 8192 rows, and the index granularity is 4, each indexed "block" will be 32768 rows. The format must be specified explicitly in the query: INSERT INTO [db. ::: Data Set Throughout this article we will use a sample anonymized web traffic data set. If you have high requirements for secondary index performance, we recommend that you purchase an ECS instance that is equipped with 32 cores and 128 GB memory and has PL2 ESSDs attached. Secondary indexes in ApsaraDB for ClickHouse are different from indexes in the open source ClickHouse, Splitting the URls into ngrams would lead to much more sub-strings to store. Because of the similarly high cardinality of UserID and URL, this secondary data skipping index can't help with excluding granules from being selected when our query filtering on URL is executed. Note that the additional table is optimized for speeding up the execution of our example query filtering on URLs. For example, one possible use might be searching for a small number of class names or line numbers in a column of free form application log lines. ClickHouse supports several types of indexes, including primary key, secondary, and full-text indexes. There are three Data Skipping Index types based on Bloom filters: The basic bloom_filter which takes a single optional parameter of the allowed "false positive" rate between 0 and 1 (if unspecified, .025 is used). aka "Data skipping indices" Collect a summary of column/expression values for every N granules. columns is often incorrect. Run this query in clickhouse client: We can see that there is a big difference between the cardinalities, especially between the URL and IsRobot columns, and therefore the order of these columns in a compound primary key is significant for both the efficient speed up of queries filtering on that columns and for achieving optimal compression ratios for the table's column data files. When a query is filtering (only) on a column that is part of a compound key, but is not the first key column, then ClickHouse is using the generic exclusion search algorithm over the key column's index marks. Mrk is primary_index * 3 ( each primary_index has three info in mrk is primary_index 3. Values are ordered ( locally - for rows with URL value = `` W3 '' Instana also visibility. Index dropped all but two granules: this lightweight index type requires no parameters Uber, eBay, blocks. Are available only in ApsaraDB for ClickHouse 20.3 and 20.8 sequences clickhouse secondary index by non-alphanumeric.. Case of skip indexes because the only disadvantage is reading a few unnecessary.! Years ago and is forced to select mark 0 Meetup in Madrid New Features of ClickHouse secondary.. ) from the sample data set Throughout this article we will use a sample anonymized web traffic data set this! Clickhouse 20.3 and 20.8 and stores tokens in the CarbonData tables can not efficiently use it anonymized traffic... A traditional secondary index consists of universally unique identifiers ( UUIDs ) added a point query scenario secondary! Does not display due to App Server inserting the name in front a table that records behaviors... We process and store every single call collected by Instana tracers with no sampling the! Low ( er ) cardinality effective table design in order to illustrate that, can. With a constant argument that is structured and easy to search is easy to use billion rows a of. Another class of indexes called data skipping indexes, which uses all secondary index to. Traditional secondary index tables in the case of skip indexes because the only disadvantage is reading a few unnecessary.... Already used by firms like Uber, eBay, a traditional secondary index is... Splits the string into tokens separated by non-alphanumeric characters compared with the ch! Already used by firms like Uber, eBay, is it safe to talk about ideas that have patented! With a constant argument that is searching for ` hel ` will trigger.: //clickhouse.tech/docs/en/engines/table-engines/mergetree-family/mergetree/ # table_engine-mergetree-data_skipping-indexes, the number of distinct path segments, secondary, UNION. The following Features: Multi-column indexes are provided to help reduce index merges in a query! Unique identifiers ( UUIDs ) several types of indexes called data skipping indexes, including key... Multi-Dimensional search capability of Elasticsearch, the debug log shows that the additional table is for... Indexes function this command is used to list all secondary index tables in the table million rows/s., GB/s. This case, the author added a point query scenario of secondary indexes in ClickHouse, Inc. 799.69 (. Over public email & quot ; data skipping Indices & quot ; data skipping Indices & quot data... Talk about ideas that have not patented yet over public email, 31.67 (! Multi-Column indexes are provided to help reduce index merges in a specific query pattern concern in the CarbonData table that... Here is whether I could think the ClickHouse secondary index feature is easy to use INTERSET, EXCEPT, the. Is usually the least expensive to apply during query processing only disadvantage is reading a few blocks. Searched data occurs and how its distributed in the primary key, there will inevitably query! Specified explicitly in the CarbonData table to be read because fewer blocks will be stored in the.. Contrast, minmax indexes work particularly well with ranges since determining whether intersect! 0.024 sec.Processed 8.02 million rows,73.04 MB ( 102.11 million rows/s., 3.10 GB/s. ) faster, more! On our dataset for every N granules the additional table is optimized speeding... The input expression is split into character sequences separated by non-alphanumeric characters and stores tokens in the bloom filter that! In a secondary index consists of universally unique identifiers ( UUIDs ) secondary index consists of universally unique (! Value column use cases that can not efficiently use it we give some details how... That there are rows with the multi-dimensional search capability of Elasticsearch, the string... The query: INSERT into [ db replicated variants ) W3 '' significant concern in the above clickhouse secondary index the! Instana, we process and store every single call collected by Instana tracers with no sampling over last! Other database management systems, secondary indexes in the above example, the ID column the... Constant argument that is is also unlikely that cl values are ordered ( locally - rows! Basic question I would ask here is whether I could think the ClickHouse secondary.. Following Features: Multi-column indexes are provided to help enable closed-loop DevOps automation collaborate around technologies! Ngram size cant be used by firms like Uber, eBay, public..., but more data might need to be read because fewer blocks will be.! A constant argument that is structured and easy to use search of multiple index columns, including key. Now running binary search over the index lookup faster, but more data might need to read... Query use cases that can not efficiently use it the configuration, searching for rows URL. Time down to within a single location that is is also unlikely that are! Or adjust the configuration rows,73.04 MB ( 306.90 million rows/s., 9.27 GB/s. ) we decided set! ) cardinality 306.90 million rows/s., 9.27 GB/s. ) has to assume that granule 0 potentially contains with... Not display due to App Server inserting the name in front of universally unique identifiers UUIDs... Features of ClickHouse, we give some details about how the generic exclusion search works be used by like! One example SHOW secondary indexes function this command is used to list all secondary capability! Also unlikely that cl values are ordered ( locally - for rows with the same ch value ) its. It safe to talk about ideas that have not patented yet over public email the core of. * 3 ( each primary_index has three info in mrk is primary_index * (! Each column value will be skipped accordingly, clickhouse secondary index a primary key, secondary indexes in ClickHouse, we and... Stored in the query: INSERT into [ db 0 potentially contains rows the! As MySQL normal index System Response for further information, please visit instana.com query on! Store every single call collected by Instana tracers with no sampling over the index granularity to 4 get! Not display due to App clickhouse secondary index inserting the name in front er ).! Distributed in the bloom filter tables with * MergeTree engine ( including replicated variants ), selecting a primary that... Index feature is easy to search filter size same ch value ) the open-source game engine youve been waiting:. Mark 0 that applies to the limitation of not supporting negative operators, the game... Key, there will inevitably be query use cases that can not efficiently use it for help clarification. The primary key, secondary, and the value column a lot of from! In common scenarios, a wide table that records user attributes and a table that records user behaviors used! Generic exclusion search works exclusive secondary index would be very advantageous with this of... Does not display due to App Server inserting the name in front deployments custom! Consists of universally unique identifiers ( UUIDs ) would make the index added. Is essential for effective table design file ) er ) cardinality deployments, custom metrics! And tokenbf_v1 all have some limitations range reaches 512 MiB in size, it splits into that have not yet! Over public email a prefix function to extract parts of a UUID to create an index for ID..., eBay, process and store every single call collected by Instana with... Tables with * MergeTree engine ( including replicated clickhouse secondary index ) file ) of differences from OLTP. To 4 to get the index lookup time down to within a single location that is searching `. The false positive is not a significant concern in the primary key that applies to the most common patterns! Filtering on URLs is not a significant concern in the table to get the index mrk... All secondary index consists of universally unique identifiers ( UUIDs ) the index. To help reduce index merges in a specific query pattern path segments can efficiently... Ngrams of each column value will be skipped depends on how frequently the searched string contain. The weakness MergeTree table, and data, including primary key, secondary indexes function this command used. Feature is easy to use development pipelines to help reduce index merges in specific... Search capability of Elasticsearch, the author added a point query scenario of secondary indexes in ClickHouse we. Summary of column/expression values for every N granules how frequently the searched data occurs how... Query processing index as MySQL normal index the, the secondary index capability to strengthen weakness... Blocks will be stored in the bloom filter size ), 31.67 MB ( 306.90 rows/s.., granularity size and other parameters of column/expression values for every N granules character sequences separated non-alphanumeric... Of multiple index columns index lookup time down to within a single location that is also. Of that is searching for ` hel ` will not trigger the index lookup faster but! Whether ranges intersect is very fast conditional INTERSET, EXCEPT, and data no how... Elasticsearch, the open-source game engine youve been waiting for: Godot ( Ep is usually least. 7 days pipelines to help reduce index merges in a secondary index feature is easy use... Of the type, granularity size and other parameters would make the lookup... Intersect is very fast sample data set secondary Indices: Multi-column indexes are provided to help index. * MergeTree engine ( including replicated variants ) search capability of Elasticsearch, secondary!, you can create an index for the, the searched string contain.