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Dump and reload gives different numbers of records
Posted by: Henry Law
Date: June 26, 2021 10:48AM

I have a simple database which contains details of files which are archived on a server. It uses MyISAM.

When copying the database to a different server I do this on the "source" server:

mysqldump -u nfb --databases nfb --no-tablespaces -r ~/NFBdb.sql -p

Then I transfer NFBdb.sql to the "target" server. It (my test machine) is running MySQL 5.7, but the production machine is running 8.0 so I have to use "sed" to edit some UTF8 stuff, with these two operations:

s/utf8mb4_0900_ai_ci/utf8_general_ci/g
s/utf8mb4/utf8/g

I then load up the test database with

mysql -u nfb -p < NFBdb.sql

Now the question. If I count the records in the "file" table in the source system this happens:

mysql -u nfb -p nfb -e 'SELECT COUNT(*) FROM file;'
+----------+
| COUNT(*) |
+----------+
| 72899 |
+----------+

But on the target system, database created directly from a dump of the source system, I have

mysql -u nfb -p nfb -e 'SELECT COUNT(*) FROM file;'
+----------+
| COUNT(*) |
+----------+
| 72819 |
+----------+

The sum of the sizes in the two databases (the total size of archived files) are off too, by about 700MB, and there's a significant mismatch in the record counts for at least one of the other tables.

Where should I start looking for whatever stupid mistake I've made?

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Dump and reload gives different numbers of records
June 26, 2021 10:48AM


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