Making indexes for jobs with very large migration records can cause OOM

12:37:26.845 WARN  d.n.h.i.d.IndexRequestServer - Unable to generate index for jobs [251947]
java.lang.OutOfMemoryError: Java heap space
        at java.util.Arrays.copyOfRange(Arrays.java:3664) ~[na:1.8.0_91]
        at java.lang.String.<init>(String.java:207) ~[na:1.8.0_91]
        at java.io.BufferedReader.readLine(BufferedReader.java:356) ~[na:1.8.0_91]
        at java.io.BufferedReader.readLine(BufferedReader.java:389) ~[na:1.8.0_91]
        at org.apache.commons.io.IOUtils.readLines(IOUtils.java:650) ~[commons-io-2.0.1.jar:2.0.1]
        at org.apache.commons.io.IOUtils.readLines(IOUtils.java:602) ~[commons-io-2.0.1.jar:2.0.1]
        at org.apache.commons.io.IOUtils.readLines(IOUtils.java:624) ~[commons-io-2.0.1.jar:2.0.1]
        at org.apache.commons.io.FileUtils.readLines(FileUtils.java:1381) ~[commons-io-2.0.1.jar:2.0.1]
        at org.apache.commons.io.FileUtils.readLines(FileUtils.java:1397) ~[commons-io-2.0.1.jar:2.0.1]
        at dk.netarkivet.harvester.indexserver.RawMetadataCache.migrateDuplicates(RawMetadataCache.java:240) ~[harvester-core-5.3.2-RC2.jar:c5b46da8634b369cb839be3e0e7e215ed1b7dd98]
        at dk.netarkivet.harvester.indexserver.RawMetadataCache.cacheData(RawMetadataCache.java:147) ~[harvester-core-5.3.2-RC2.jar:c5b46da8634b369cb839be3e0e7e215ed1b7dd98]
        at dk.netarkivet.harvester.indexserver.RawMetadataCache.cacheData(RawMetadataCache.java:56) ~[harvester-core-5.3.2-RC2.jar:c5b46da8634b369cb839be3e0e7e215ed1b7dd98]
        at dk.netarkivet.harvester.indexserver.FileBasedCache.cache(FileBasedCache.java:146) ~[harvester-core-5.3.2-RC2.jar:c5b46da8634b369cb839be3e0e7e215ed1b7dd98]
        at dk.netarkivet.harvester.indexserver.FileBasedCache.get(FileBasedCache.java:174) ~[harvester-core-5.3.2-RC2.jar:c5b46da8634b369cb839be3e0e7e215ed1b7dd98]
        at dk.netarkivet.harvester.indexserver.CombiningMultiFileBasedCache.prepareCombine(CombiningMultiFileBasedCache.java:88) ~[harvester-core-5.3.2-RC2.jar:c5b46da8634b369cb839be3e0e7e215ed1b7dd98]
        at dk.netarkivet.harvester.indexserver.CrawlLogIndexCache.prepareCombine(CrawlLogIndexCache.java:106) ~[harvester-core-5.3.2-RC2.jar:c5b46da8634b369cb839be3e0e7e215ed1b7dd98]
        at dk.netarkivet.harvester.indexserver.CombiningMultiFileBasedCache.cacheData(CombiningMultiFileBasedCache.java:69) ~[harvester-core-5.3.2-RC2.jar:c5b46da8634b369cb839be3e0e7e215ed1b7dd98]
        at dk.netarkivet.harvester.indexserver.CombiningMultiFileBasedCache.cacheData(CombiningMultiFileBasedCache.java:43) ~[harvester-core-5.3.2-RC2.jar:c5b46da8634b369cb839be3e0e7e215ed1b7dd98]
        at dk.netarkivet.harvester.indexserver.FileBasedCache.cache(FileBasedCache.java:146) ~[harvester-core-5.3.2-RC2.jar:c5b46da8634b369cb839be3e0e7e215ed1b7dd98]
        at dk.netarkivet.harvester.indexserver.distribute.IndexRequestServer.doProcessIndexRequestMessage(IndexRequestServer.java:336) [harvester-core-5.3.2-RC2.jar:c5b46da8634b369cb839be3e0e7e215ed1b7dd98]
        at dk.netarkivet.harvester.indexserver.distribute.IndexRequestServer.access$000(IndexRequestServer.java:76) [harvester-core-5.3.2-RC2.jar:c5b46da8634b369cb839be3e0e7e215ed1b7dd98]
        at dk.netarkivet.harvester.indexserver.distribute.IndexRequestServer$2.run(IndexRequestServer.java:238) [harvester-core-5.3.2-RC2.jar:c5b46da8634b369cb839be3e0e7e215ed1b7dd98]
12:37:26.847 INFO  d.n.h.i.d.IndexRequestServer - Sending failed reply for IndexRequestMessage back to sender '[Queue 'PROD_COMMON_THIS_INDEX_CLIENT_130_226_228_70_VP_8094']'.