How to re-attach a Stardog database?

Support
1

I have a database (mydatabase) that was created on a dedicated, persistent volume (in a public cloud environment). e.g. created in $STARDOG_HOME/mydatabase where the data disk was mounted. Meanwhile, the system database was lost because it was backed by an ephemeral disk. I figured that I could simply recreate the database and that the existing data would survive; it did not.

Not to worry, it was a test environment (Stardog 5.3.2), but I’d like to know if, in concept, it is possible to re-attach a database. Here’s the error that was produced:

ERROR 2018-08-05 18:16:12,949 [Stardog.Executor-17] com.complexible.stardog.dht.dictionary.HashDictionary:compareSizes(352): Dictionary corruption 0 != 34767
WARN  2018-08-05 18:16:13,018 [Stardog.Executor-17] com.complexible.stardog.dht.dictionary.HashDictionary:<init>(271): Dictionary is corrupted, will try to repair automatically
java.io.IOException: Dictionary file is corrupt, rebuild the database
	at com.complexible.stardog.dht.dictionary.HashDictionary.compareSizes(HashDictionary.java:353) ~[stardog-5.3.2.jar:?]
	at com.complexible.stardog.dht.dictionary.HashDictionary.<init>(HashDictionary.java:263) ~[stardog-5.3.2.jar:?]
	at com.complexible.stardog.dht.dictionary.HashDictionary$Builder.build(HashDictionary.java:160) ~[stardog-5.3.2.jar:?]
	at com.complexible.stardog.dht.dictionary.HashDictionary$Builder.build(HashDictionary.java:114) ~[stardog-5.3.2.jar:?]
	at com.complexible.stardog.index.dictionary.InliningMappingDictionary$Builder.build(InliningMappingDictionary.java:53) ~[stardog-5.3.2.jar:?]
...

Thanks for insight!

2

In theory, you can perform a stardog-admin db create command on the new (empty) home, shut down your server, copy the old data dir into the new home, and restart, and the database should be back

3

Thanks Stephen, this suggests that a stardog-admin db attach command would be easy to build.

4

Right, except this will not work with the new storage backend coming in Stardog 6 (currently in the alpha stage) because database data won’t be in a separate directory any more. The principled way to preserve (and restore) data is backups.

Best,
Pavel

5

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