On T372677, we have a process that queries the `revision` table of all currently open and public wikis.
Out of that current set of 867 wikis, there are 10 wikis that, for some reason, have some rows in which the `rev_timestamp` column is full of spaces rather than having a MW timestamp as per https://www.mediawiki.org/wiki/Manual:Revision_table#rev_timestamp.
On P70617, @Krinkle did an analysis of the content of these rows for the `chrwiktionary ` wiki , of which I copy part here:
```
wikiadmin2023@10.64.48.160(chrwiktionary)> SELECT rev_id, rev_page, IFNULL(rev_timestamp,"NULL") FROM revision WHERE rev_id IN (1601,1602,1604);
+--------+----------+------------------------------+
| rev_id | rev_page | IFNULL(rev_timestamp,"NULL") |
+--------+----------+------------------------------+
| 1601 | 1 | |
| 1602 | 2 | |
| 1604 | 4 | |
+--------+----------+------------------------------+
3 rows in set (0.004 sec)
wikiadmin2023@10.64.48.160(chrwiktionary)> SELECT rev_id, rev_page, LENGTH(rev_timestamp) FROM revision WHERE rev_id IN (1601,1602,1604);
+--------+----------+-----------------------+
| rev_id | rev_page | LENGTH(rev_timestamp) |
+--------+----------+-----------------------+
| 1601 | 1 | 14 |
| 1602 | 2 | 14 |
| 1604 | 4 | 14 |
+--------+----------+-----------------------+
3 rows in set (0.001 sec)
```
There is also evidence of this issue being around at least since Jan 2015 as per {T86478}.
The list of affected wikis is:
```
chrwiktionary
csbwiki
foundationwiki
iowiki
roa_rupwiki
roa_rupwiktionary
scwiki
simplewiki
tpiwiki
zh_min_nanwiki
```
Note again our process only hits currently open and public wikis. There may be more hits on closed and/or private wikis.