Meet the new Glide Apps
Glide Pages are now Glide Apps. Please refer to this article for up-to-date information, as some of this documentation is outdated.
In Google Sheets, rows don't really have an identity apart from their row number. In the image below we can see that the talk State of UX is located in row 4.
This is fine, but if you add, move or delete rows, that row's location will change. In the image below State of UX starts off in row 4 and ends up in row 3.
In some circumstances this is fine, but if you have components like Comments and Favorite or use Relations (that need to know the exact location of a row) and then the row number changes, these components will be confused as they are only looking at row numbers.
In the image below, you can see this happen with the Favorite component after we delete some rows from our sheet. After we delete them, the item we favorited changes to a totally different talk.
Unique Identifier
The way to solve this issue is by giving each row a Unique Identifier. In other words, a value in a column that will always be different for each row. And the easiest way to do this in Glide is by using the Row ID column in the data editor.
If you don't have a Row ID column in your table, components like Comments and Favorite will ask you to set a Key or a Topic. This is a manual way for you to connect that component with a column of unique values in your sheet so it can keep track of that row. The Row ID column is the best way of doing this.