When enabling the schema validation through hibernate.hbm2ddl.auto=validate, starting from ORM 5.4.0.CR1 up to 5.4.5.Final, due to HHH-12973 Closed fix and 1db476dbd5ec4f852472b953d50a8caa073efd6d commit, the validation of a sequence not being of BIGINT type fails.

In class org.hibernate.tool.schema.extract.internal.SequenceInformationExtractorLegacyImpl, method extractMetadata() calls resultSetStartValueSize() that in turn calls resultSet.getLong(column).
If the sequence is defined as
{{
CREATE SEQUENCE [dbo].[SampleSequence]
AS [int]
START WITH 1
INCREMENT BY 1
MINVALUE 1
MAXVALUE 100
}}
the underlying jdbc type will be INT, resulting in a java.lang.Integer and causing this exception during schema validation (even if that sequence is not used at all):

{{javax.persistence.PersistenceException: [PersistenceUnit: PromagWMS] Unable to build Hibernate SessionFactory
at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.persistenceException(EntityManagerFactoryBuilderImpl.java:1012) ~[hibernate-core-5.4.5.Final.jar:5.4.5.Final]
at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.build(EntityManagerFactoryBuilderImpl.java:938) ~[hibernate-core-5.4.5.Final.jar:5.4.5.Final]
at org.hibernate.jpa.HibernatePersistenceProvider.createEntityManagerFactory(HibernatePersistenceProvider.java:56) ~[hibernate-core-5.4.5.Final.jar:5.4.5.Final]
at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:79) ~[javax.persistence-api-2.2.jar:2.2]
... 4 more [...]
Caused by: java.lang.ClassCastException: java.lang.Integer cannot be cast to java.lang.Long
at com.microsoft.sqlserver.jdbc.SQLServerResultSet.getLong(SQLServerResultSet.java:2328) ~[mssql-jdbc-7.4.1.jre8.jar:?]
at com.zaxxer.hikari.pool.HikariProxyResultSet.getLong(HikariProxyResultSet.java) ~[HikariCP-3.4.1.jar:?]
at org.hibernate.tool.schema.extract.internal.SequenceInformationExtractorLegacyImpl.resultSetStartValueSize(SequenceInformationExtractorLegacyImpl.java:129) ~[hibernate-core-5.4.5.Final.jar:5.4.5.Final]
at org.hibernate.tool.schema.extract.internal.SequenceInformationExtractorLegacyImpl.extractMetadata(SequenceInformationExtractorLegacyImpl.java:59) ~[hibernate-core-5.4.5.Final.jar:5.4.5.Final]
at org.hibernate.tool.schema.extract.internal.DatabaseInformationImpl.initializeSequences(DatabaseInformationImpl.java:65) ~[hibernate-core-5.4.5.Final.jar:5.4.5.Final]
at org.hibernate.tool.schema.extract.internal.DatabaseInformationImpl.<init>(DatabaseInformationImpl.java:59) ~[hibernate-core-5.4.5.Final.jar:5.4.5.Final]
at org.hibernate.tool.schema.internal.Helper.buildDatabaseInformation(Helper.java:155) ~[hibernate-core-5.4.5.Final.jar:5.4.5.Final]
at org.hibernate.tool.schema.internal.AbstractSchemaValidator.doValidation(AbstractSchemaValidator.java:61) ~[hibernate-core-5.4.5.Final.jar:5.4.5.Final]
at org.hibernate.tool.schema.spi.SchemaManagementToolCoordinator.performDatabaseAction(SchemaManagementToolCoordinator.java:192) ~[hibernate-core-5.4.5.Final.jar:5.4.5.Final]
at org.hibernate.tool.schema.spi.SchemaManagementToolCoordinator.process(SchemaManagementToolCoordinator.java:73) ~[hibernate-core-5.4.5.Final.jar:5.4.5.Final]
at org.hibernate.internal.SessionFactoryImpl.<init>(SessionFactoryImpl.java:320) ~[hibernate-core-5.4.5.Final.jar:5.4.5.Final]
at org.hibernate.boot.internal.SessionFactoryBuilderImpl.build(SessionFactoryBuilderImpl.java:462) ~[hibernate-core-5.4.5.Final.jar:5.4.5.Final]
at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.build(EntityManagerFactoryBuilderImpl.java:935) ~[hibernate-core-5.4.5.Final.jar:5.4.5.Final]
at org.hibernate.jpa.HibernatePersistenceProvider.createEntityManagerFactory(HibernatePersistenceProvider.java:56) ~[hibernate-core-5.4.5.Final.jar:5.4.5.Final]
at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:79) ~[javax.persistence-api-2.2.jar:2.2]
... 4 more [...]
}}

My workaround for MSSQL and my specific use-case, is just to change the sequence query string by using a custom dialect that converts columns into BIGINT type:
{{@Override
public String getQuerySequencesString()

}}

Since class SequenceInformationExtractorLegacyImpl just casts those columns to java.lang.Long, I think a similar approach should be taken for every possible dialect...