Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

docs: Correct concat rechunk in user guide #18080

Merged
merged 1 commit into from
Aug 8, 2024
Merged

docs: Correct concat rechunk in user guide #18080

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
4 changes: 2 additions & 2 deletions docs/user-guide/transformations/concatenation.md
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -56,5 +56,5 @@ When the dataframe shapes do not match and we have an overlapping semantic key t

## Rechunking

Before a concatenation we have two dataframes `df1` and `df2`. Each column in `df1` and `df2` is in one or more chunks in memory. By default, during concatenation the chunks in each column are copied to a single new chunk - this is known as **rechunking**. Rechunking is an expensive operation, but is often worth it because future operations will be faster.
If you do not want Polars to rechunk the concatenated `DataFrame` you specify `rechunk = False` when doing the concatenation.
Before a concatenation we have two dataframes `df1` and `df2`. Each column in `df1` and `df2` is in one or more chunks in memory. By default, during concatenation the chunks in each column are not made contiguous. This makes the concat operation faster and consume less memory but it may slow down future operations that would benefit from having the data be in contiguous memory. The process of copying the fragmented chunks into a single new chunk is known as **rechunking**. Rechunking is an expensive operation. Prior to version 0.20.26, the default was to perform a rechunk but in new versions, the default is not to.
If you do want Polars to rechunk the concatenated `DataFrame` you specify `rechunk = True` when doing the concatenation.