Increasing Aggregate Field Length#
Warning
ODK Aggregate is no longer being updated. Please use ODK Central instead.
By default, Aggregate's datastore layer limits text values to 255 characters or less. If a submission includes a value longer than 255 characters, those additional characters are not saved in the database and no warning is shown. That means there is a risk of data loss when using question types that save long text values such as geotrace, geoshape or select multiple. This limitation exists for performance reasons, particularly for older versions of MySQL.
It is possible to set the desired database field length for a particular question. This value can go up to about 16000 UTF-8 characters but the datastore storage efficiency may get worse as the value increases. If you go over 16000 characters, be sure to do an end-to-end test to ensure the performance is acceptable.
Tip
Each geopoint is roughly 50 characters, so a geotrace or geoshape with a length of 16000 will store about 320 points.
In an XLSForm, the database field length is set from the bind::odk:length column. On form upload, Aggregate will adjust the database field length of questions that have a whole number in that column. Other questions will get a default length of 255.
XLSForm
type |
name |
label |
bind::odk:length |
|---|---|---|---|
select_multiple opt_abc |
multi |
Select multi |
500 |
geoshape |
shape |
Select an area |
1000 |
list_name |
name |
label |
|---|---|---|
opt_abc |
a |
A |
opt_abc |
b |
B |
opt_abc |
c |
C |