Why does Liquibase want to dropPrimaryKey and addPrimaryKey?

I have Postgres databases generated with Eclipse Link. Between these databases is not any change, but when I run liquibase for generating diffChangeLog, it generates changesets with dropPrimaryKey and addPrimaryKey. I don't understand why it generates these records for all primary keys of all tables. Names, order of columns are the same for both tables.

Example of changeset

1. <changeSet author="michal2 (generated)" id="1436872322297-8">
           <dropPrimaryKey tableName="country_translation"/>
           <addPrimaryKey columnNames="country_id, translations_id" constraintName="country_translation_pkey" tableName="country_translation"/>
       </changeSet>

Sql of original table

1. CREATE TABLE country_translation
   (
     country_id bigint NOT NULL,
     translations_id bigint NOT NULL,
     CONSTRAINT country_translation_pkey PRIMARY KEY (country_id, translations_id),
     CONSTRAINT fk_country_translation_country_id FOREIGN KEY (country_id)
         REFERENCES country (id) MATCH SIMPLE
         ON UPDATE NO ACTION ON DELETE NO ACTION,
     CONSTRAINT fk_country_translation_translations_id FOREIGN KEY (translations_id)
         REFERENCES translation (id) MATCH SIMPLE
         ON UPDATE NO ACTION ON DELETE NO ACTION
   )
   WITH (
     OIDS=FALSE
   );
   ALTER TABLE country_translation
     OWNER TO hotels;

Sql of reference table

1. CREATE TABLE country_translation
   (
     country_id bigint NOT NULL,
     translations_id bigint NOT NULL,
     CONSTRAINT country_translation_pkey PRIMARY KEY (country_id, translations_id),
     CONSTRAINT fk_country_translation_country_id FOREIGN KEY (country_id)
         REFERENCES country (id) MATCH SIMPLE
         ON UPDATE NO ACTION ON DELETE NO ACTION,
     CONSTRAINT fk_country_translation_translations_id FOREIGN KEY (translations_id)
         REFERENCES translation (id) MATCH SIMPLE
         ON UPDATE NO ACTION ON DELETE NO ACTION
   )
   WITH (
     OIDS=FALSE
   );
   ALTER TABLE country_translation
     OWNER TO hotels;

Liquibase command with arguments

1. ./liquibase \
         --driver=org.postgresql.Driver \
         --classpath=/home/michal2/tools/postgresql-jdbc-driver/postgresql-jdbc.jar \
         --changeLogFile=changelog-hotels.xml \
         --url="jdbc:postgresql://localhost/hotels" \
         --username=hotels \
         --password=hotels \
         --defaultSchemaName=public \
       --logLevel=info \
       diffChangeLog \
       --referenceUrl="jdbc:postgresql://localhost/hotels_liquibase" \
       --referenceUsername=hotels \
       --referencePassword=hotels \
           --referenceDefaultSchemaName=public
   

I'm using version 3.4.0