Blog

This Week in Databend #81

PsiACEFeb 15, 2023

Databend is a modern cloud data warehouse, serving your massive-scale analytics needs at low cost and complexity. Open source alternative to Snowflake. 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.

Accepted RFCs :airplane_departure:

rfc: query result cache (#10014)

Features & Improvements ✨

Planner

support
```
EXPLAIN ANALYZE
```
statement to profile query execution (#10023)
derive new filter and push down (#10021)

Query

alter table add/drop column SQL support (#9851)
new table function
```
infer_schema
```
(#9936)
add privilege check for select (#9924)
improve signed numeric keys (#9978)
support to parse jwt metadata and add multiple identity issuer configuration (#9971)
support create file format (#10009)

Storage

adopt OpenDAL's native scan support (#9985)
add drop_table_by_id api (#9990)

Expression

add operation for decimal (#9926)

Functions

support
```
array_any
```
function (#9953)
support
```
array_sort
```
(#9941)

Sqllogictest

add time travel test for alter table (#9939)

Code Refactoring 🎉

Meta

move application level types such as user/role/storage-config to crate common-meta/app (#9944)
fix abuse of ErrorCode (#10056)

Query

use
```
transform_sort_merge
```
use heap to sort blocks (#10047)

Storage

introduction of FieldIndex and ColumnId types for clear differentiation of use (#10017)

Build/Testing/CI Infra Changes 🔌

run benchmark for clickbench result format (#10019)
run benchmark both s3 & fs (#10050)

Bug Fixes 🔧

Privilege

add privileges on system.one to PUBLIC by default (#10040)

Catalog

parts was not distributed evenly (#9951)

Planner

type assertion failed on subquery (#9937)
enable outer join to inner join optimization (#9943)
fix limit pushdown outer join (#10043)

Query

fix add column update bug (#10037)

Storage

fix sub-column of added-tuple column return default 0 bug (#9973)
new bloom filter that bind index with Column Id instead of column name (#10022)

What's On In Databend

Stay connected with the latest news about Databend.

RFC: Query Result Cache

Caching the results of queries against data that doesn't update frequently can greatly reduce response time. Once cached, the result will be returned in a much shorter time if you run the query again.

How to Write a Scalar / Aggregate Function

Did you know that you can enhance the power of Databend by creating your own scalar or aggregate functions? Fortunately, it's not a difficult task!

The following guides are intended for Rust developers and Databend users who want to create their own workflows. The guides provide step-by-step instructions on how to create and register your own functions using Rust, along with code snippets and examples of various types of functions to walk you through the process.

Profile-Guided Optimization

Profile-guided optimization (PGO) is a compiler optimization technique that collects execution data during the program runtime and allows for tailoring optimizations tailored to both hot and cold code paths.

In this blog, we'll guide you through the process of optimizing Databend binary builds using PGO. We'll use Databend's SQL logic tests as an example to illustrate the step-by-step procedure.

Please note that PGO always requires generating perf data using workloads that are statistically representative. However, there's no guarantee that performance will always improve. Decide whether to use it based on your actual needs.

Learn More

Blog | Optimizing Databend Binary Builds with Profile-guided Optimization

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.

To make our documentation clearer and easier to understand, we plan to restructure our function-related documentation to follow the same format as DuckDB's documentation. This involves breaking down the task into smaller sub-tasks based on function categories, so that anyone who wants to help improve Databend's documentation can easily get involved.

Issue 10029: Tracking: re-org the functions doc

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