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diff --git a/docs/_posts/2024-03-29-prql-support.md b/docs/_posts/2024-03-29-prql-support.md new file mode 100644 index 0000000..98df8e6 --- /dev/null +++ b/docs/_posts/2024-03-29-prql-support.md @@ -0,0 +1,51 @@ +--- +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. |