mirror of
https://github.com/tstack/lnav
synced 2024-11-17 15:29:40 +00:00
52 lines
2.5 KiB
Markdown
52 lines
2.5 KiB
Markdown
|
---
|
||
|
|
layout: post
|
||
|
|
title: Support for the PRQL in the database query prompt
|
||
|
|
excerpt: >-
|
||
|
|
PRQL is a database query language that is pipeline-oriented
|
||
|
|
and easier to use interactively
|
||
|
|
---
|
||
|
|
|
||
|
|
The v0.12.1 release of lnav includes support for
|
||
|
|
[PRQL](https://prql-lang.org). PRQL is a database query language
|
||
|
|
that has a pipeline-oriented syntax. The main advantage of PRQL,
|
||
|
|
in the context of lnav, is that it is easier to work with
|
||
|
|
interactively compared to SQL. For example, lnav can provide
|
||
|
|
previews of different stages of the pipeline and provide more
|
||
|
|
accurate tab-completions for the columns in the result set. I'm
|
||
|
|
hoping that the ease-of-use will make doing log analysis in lnav
|
||
|
|
much easier.
|
||
|
|
|
||
|
|
You can execute a PRQL query using the existing database prompt
|
||
|
|
(press `;`). A query is interpreted as PRQL if it starts with
|
||
|
|
the [`from`](https://prql-lang.org/book/reference/data/from.html)
|
||
|
|
keyword. After `from`, the database table should be provided.
|
||
|
|
The table for the focused log message will be suggested by default.
|
||
|
|
You can accept the suggestion by pressing TAB. To add a new stage
|
||
|
|
to the pipeline, enter a pipe symbol (`|`), followed by a
|
||
|
|
[PRQL transform](https://prql-lang.org/book/reference/stdlib/transforms/index.html)
|
||
|
|
and its arguments. In addition to the standard set of transforms,
|
||
|
|
lnav provides some convenience transforms in the `stats` and `utils`
|
||
|
|
namespaces. For example, `stats.count_by` can be passed one or more
|
||
|
|
column names to group by and count, with the result sorted by most
|
||
|
|
to least.
|
||
|
|
|
||
|
|
As you enter a query, lnav will update various panels on the display
|
||
|
|
to show help, preview data, and errors. The following is a
|
||
|
|
screenshot of lnav viewing a web access log with a query in progress:
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
The top half is the usual log message view. Below that is the online
|
||
|
|
help panel showing the documentation for the `stats.count_by` PRQL
|
||
|
|
function. lnav will show the help for what is currently under the
|
||
|
|
cursor. The next panel shows the preview data for the pipeline stage
|
||
|
|
that precedes the stage where the cursor is. In this case, the
|
||
|
|
results of `from access_log`, which is the contents of the access
|
||
|
|
log table. The second preview window shows the result of the
|
||
|
|
pipeline stage where the cursor is located.
|
||
|
|
|
||
|
|
There is still a lot of work to be done on the integration and PRQL
|
||
|
|
itself, but I'm very hopeful this will work out well in the long
|
||
|
|
term. Many thanks to the PRQL team for starting the project and
|
||
|
|
keeping it going, it's not easy competing with SQL.
|