When new rows fail or get wrong ids.
WHAT AUTO-INCREMENT IS
The counter assigning the next id when a row is inserted.
THE COMMON PROBLEM
After a partial restore or a manual insert, the counter can be lower than the highest existing id.
The next insert then attempts an id that already exists, producing a duplicate key error.
THE SYMPTOM
Duplicate entry errors on the primary key, when inserting new content, for no apparent reason.
THE FIX
Set the auto-increment value above the highest existing id.
The Operations tab for the table has an AUTO_INCREMENT field.
Find the highest id first:
SELECT MAX(id) FROM table;
Set the counter to at least one above it.
THE OTHER CASE
Gaps in ids. These are normal and harmless: deleted rows leave gaps, and failed inserts consume numbers.
Do not attempt to renumber to close gaps. Other tables reference those ids.
AFTER A RESTORE
Check this if inserts start failing immediately afterwards.
