Installer database upgrade script (install -d) scans every RRD directory, bombs with "too many open files"

Attempting to upgrade from 1.9.92 snapshot to 1.9.94 snapshot, and install -d bombed with this error:

• Running migration for changelog: URL [jar:file:/opt/opennms/lib/org.opennms.core.schema-1.9.94-SNAPSHOT-liquibase.jar!/changelog.xml]
  Exception in thread "main" org.opennms.core.schema.MigrationException: unable to migrate the database
  at org.opennms.core.schema.Migrator.migrate(Migrator.java:473)
  at org.opennms.install.Installer.install(Installer.java:255)
  at org.opennms.install.Installer.main(Installer.java:950)
  Caused by: org.postgresql.util.PSQLException: The connection attempt failed.
  at org.postgresql.core.v3.ConnectionFactoryImpl.openConnectionImpl(ConnectionFactoryImpl.java:150)
  at org.postgresql.core.ConnectionFactory.openConnection(ConnectionFactory.java:66)
  at org.postgresql.jdbc2.AbstractJdbc2Connection.<init>(AbstractJdbc2Connection.java:125)
  at org.postgresql.jdbc3.AbstractJdbc3Connection.<init>(AbstractJdbc3Connection.java:30)
  at org.postgresql.jdbc3.Jdbc3Connection.<init>(Jdbc3Connection.java:24)
  at org.postgresql.Driver.makeConnection(Driver.java:393)
  at org.postgresql.Driver.connect(Driver.java:267)
  at java.sql.DriverManager.getConnection(DriverManager.java:579)
  at java.sql.DriverManager.getConnection(DriverManager.java:190)
  at org.opennms.netmgt.dao.db.SimpleDataSource.getConnection(SimpleDataSource.java:90)
  at org.opennms.core.schema.Migrator.migrate(Migrator.java:458)
  ... 2 more
  Caused by: java.net.SocketException: Too many open files
  at java.net.Socket.createImpl(Socket.java:447)
  at java.net.Socket.<init>(Socket.java:421)
  at java.net.Socket.<init>(Socket.java:208)
  at org.postgresql.core.PGStream.<init>(PGStream.java:62)
  at org.postgresql.core.v3.ConnectionFactoryImpl.openConnectionImpl(ConnectionFactoryImpl.java:76)
  ... 12 more