HHH-13106 : Fixes schema validation failure with PostgreSQL 10

[kedar-joshi]

Few months ago, commit 1db476d included the fixes for HHH-12973. This commit also added the following change in PostgreSQL81Dialect.java

@Override
public String getQuerySequencesString() {
	// return "select relname from pg_class where relkind='S'"; // Removed
	return "select * from information_schema.sequences"; // Added
}

Few months later, commit 76981d9 added support for default generated identity columns introduced in PostgreSQL 10. See HHH-13202 for details. Unfortunately select * from information_schema.sequences doesn't return implicit sequences generated for default identity columns.

The combined effect of these two changes was that the SequenceInformationExtractor::extractMetadata returned incorrect number of sequences. Especially, the implicit sequences were no longer visible to Hibernate. This resulted in HHH-13106 where setting hibernate.hbm2ddl.auto to validate would make application to fail with exception Schema-validation: missing sequence.

This PR tried to find a common ground between these changes to restore expected behavior.

[kedar-joshi]

Is there any plan to merge this ?

[vellotis]

I'll second kedar-joshi.

Is there any plan to fix-merge this?

[kislyakdmitry]

Guys, are you planning to merge this one or fix this issue in another PR?
This issue is still reproducible

[beikov]

The test uses an entity with a sequence generator but the DDL uses identity generation. Obviously, there is a mismatch here and I don't see a bug. When you use @GeneratedValue(strategy = IDENTITY) on the entity along with generated always as identity, the validation will work.

No bug here, so I'll close this.

[beikov]

Also see #5530