Wrong key 'history_text_3' in table 'history_text' after upgrade from 2.2.18 to 3.4.3

[lentyai]

Hello,

Yesterday after zabbix upgrade from 2.2.18 to 3.4.3 I saw a lot of messages in log file like

2353:20171222:115113.674 [Z3005] query failed: [1062] Duplicate entry '1513943473' for key 'history_text_3' [insert into history_text (itemid,clock,ns,value) values (5105100009092720,1513943473,86941377,'NO FAILURES'),(5105100009092722,1513943473,86941377,' NO SUCCESSES');

In database I found that unique key 'history_text_3' contains only 'clock' field. Why? This is EPOCH value. Zabbix can collect a lot of values in one second.
What's happened?

I guess, I can remove this key from the table without any negative effect.

[volter]

Any chance somebody created this manually? I can't find any reference to it. A look at the 3.4 schema SQL indicates, that no such index should exist. And for the sake of completeness, there's the ns column too, that contains nanoseconds, so this constraint would not even be complete.

[lentyai]

Any chance somebody created this manually? I can't find any reference to it.

Hm. It's possible. I don't find such index in sources schema from Zabbix 2.0.10. But nobody knows when it was created. In this case, I can drop this index before upgrade.