update script causing oom

oom_update.py

import elasticsearch

es = elasticsearch.Elasticsearch()

for i in range(10000):
    es.index(index="testidx", doc_type="doc", id=i, body= "{\"testfield\":\"a\"}")
es.indices.refresh()

for i in range(10000):
    updateScript = "ctx._source.testfield += \" " + str(i) + "\""
    updatebody = {"script": updateScript, "lang": "groovy"}
    es.update(index="testidx", doc_type="doc", id=i, body= updatebody)