This Week in Databend #74

December 28, 2022 · 3 min read

PsiACE

Databend is a powerful cloud data warehouse. Built for elasticity and efficiency. Free and open. Also available in the cloud: .

Databend is a powerful cloud data warehouse. Built for elasticity and efficiency. Free and open. Also available in the cloud: https://app.databend.com .

What's New

Check out what we've done this week to make Databend even better for you.

Features & Improvements ✨

Meta

remove stream when a watch client is dropped (#9334)

Planner

support selectivity estimation for range predicates (#9398)

Query

support copy on error (#9312)
support databend-local (#9282)
external storage support location part prefix (#9381)

Storage

rangefilter support in (#9330)
try to improve object storage io read (#9335)
support table compression (#9370)

Metrics

add more metrics for fuse compact and block write (#9399)

Sqllogictest

add no-fail-fast support (#9391)

Code Refactoring 🎉

adopt rustls entirely, removing all deps to native-tls (#9358)

Format

remove format_xxx settings (#9360)
adjust interface of FileFormatOptionsExt (#9395)

Planner

remove SyncTypeChecker (#9352)

Query

split fuse source to read data and deserialize (#9353)
avoid io copy in read parquet data (#9365)
add uncompressed buffer for parquet reader (#9379)

Storage

add read/write settings (#9359)

Bug Fixes 🔧

Format

fix align_flush with header only (#9327)

Settings

use logical CPU number as default value of num_cpus (#9396)

Processors

the data type on both sides of the union does not match (#9361)

HTTP Handler

false alarm (warning log) about query not exists (#9380)

Sqllogictest

refactor sqllogictest http client and fix expression string like (#9363)

What's On In Databend

Stay connected with the latest news about Databend.

Introducing databend-local

Inspired by clickhouse-local, databend-local allows you to perform fast processing on local files, without the need of launching a Databend cluster.

> export CONFIG_FILE=tests/local/config/databend-local.toml
> cargo run --bin=databend-local -- --sql="SELECT * FROM tbl1" --table=tbl1=/path/to/databend/docs/public/data/books.parquet

exec local query: SELECT * FROM tbl1
+------------------------------+---------------------+------+
| title                        | author              | date |
+------------------------------+---------------------+------+
| Transaction Processing       | Jim Gray            | 1992 |
| Readings in Database Systems | Michael Stonebraker | 2004 |
| Transaction Processing       | Jim Gray            | 1992 |
| Readings in Database Systems | Michael Stonebraker | 2004 |
+------------------------------+---------------------+------+
4 rows in set. Query took 0.015 seconds.

Learn More

PR | support databend-local

What's Up Next

We're always open to cutting-edge technologies and innovative ideas. You're more than welcome to join the community and bring them to Databend.

Compressing Short Strings

When processing the same queries with short strings involved, Databend usually reads more data than other databases, such as Snowflake.

SELECT SearchPhrase, MIN(URL), COUNT(*) AS c FROM hits WHERE URL LIKE '%google%' AND SearchPhrase <> '' GROUP BY SearchPhrase ORDER BY c DESC LIMIT 10;

Such queries might be more efficient if short strings (URLs, etc) are compressed.

Issue 9001: performance: compressing for short strings

Please let us know if you're interested in contributing to this issue, or pick up a good first issue at https://link.databend.rs/i-m-feeling-lucky to get started.