# Is it possible to use String as \_id? **URL:** \ **Category:** Elasticsearch\ **Created:** [April 28, 2014, 2:39pm UTC](https://discuss.elastic.co/t/is-it-possible-to-use-string-as--id/17236 "2014-04-28T14:39:33Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![Yz1](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/yz1/32/1611_2.png) [@Yz1](https://discuss.elastic.co/u/Yz1)\ **Post date:** [April 28, 2014, 2:39pm UTC](https://discuss.elastic.co/t/is-it-possible-to-use-string-as--id/17236/1 "2014-04-28T14:39:33Z")
Through my experiment, it seems not possible to use string as primary key in Elasticsearch. If type String is used , then the \_id will be something like this: "\_id":"[B@fe583b" which uses the object address in jvm instead of the real value. So, is there any way to generate a composite \_id from two integer value? -- You received this message because you are subscribed to the Google Groups "elasticsearch" group. To unsubscribe from this group and stop receiving emails from it, send an email to [elasticsearch+unsubscribe@googlegroups.com](mailto:elasticsearch+unsubscribe@googlegroups.com). To view this discussion on the web visit [https://groups.google.com/d/msgid/elasticsearch/f073e04b-f2a1-4e5a-a7e0-ff93727f6e9f%40googlegroups.com](https://groups.google.com/d/msgid/elasticsearch/f073e04b-f2a1-4e5a-a7e0-ff93727f6e9f%40googlegroups.com). For more options, visit [https://groups.google.com/d/optout](https://groups.google.com/d/optout). ---
**Author:** ![brian\_yoder](https://avatars.discourse-cdn.com/v4/letter/b/f1d935/32.png) [@brian\_yoder](https://discuss.elastic.co/u/brian_yoder)\ **Post date:** [April 28, 2014, 2:56pm UTC](https://discuss.elastic.co/t/is-it-possible-to-use-string-as--id/17236/2 "2014-04-28T14:56:57Z")
The \_id (metadata \_id, that is) is a string value. The value of the \_id string is whatever you set it to (or else a long string automatically generated by Elasticsearch when the document is created). You have complete freedom to set it to any string value you wish. The \_id metadata is the closest thing ES has to a unique constraint, and I use it quite effectively in this way. Brian -- You received this message because you are subscribed to the Google Groups "elasticsearch" group. To unsubscribe from this group and stop receiving emails from it, send an email to [elasticsearch+unsubscribe@googlegroups.com](mailto:elasticsearch+unsubscribe@googlegroups.com). To view this discussion on the web visit [https://groups.google.com/d/msgid/elasticsearch/a311ee25-b4e9-4155-9543-55eb7a199bcd%40googlegroups.com](https://groups.google.com/d/msgid/elasticsearch/a311ee25-b4e9-4155-9543-55eb7a199bcd%40googlegroups.com). For more options, visit [https://groups.google.com/d/optout](https://groups.google.com/d/optout). ---
**Author:** ![jpountz](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/jpountz/32/45836_2.png) [@jpountz](https://discuss.elastic.co/u/jpountz)\ **Post date:** [April 28, 2014, 3:00pm UTC](https://discuss.elastic.co/t/is-it-possible-to-use-string-as--id/17236/3 "2014-04-28T15:00:42Z")
Can you share the code that you used to trigger this issue? On Mon, Apr 28, 2014 at 4:39 PM, Yz [yingzhong.xu@gmail.com](mailto:yingzhong.xu@gmail.com) wrote: > Through my experiment, it seems not possible to use string as primary key > in Elasticsearch. > If type String is used , then the \_id will be something like this: > "\_id":"[B@fe583b" > which uses the object address in jvm instead of the real value. > So, is there any way to generate a composite \_id from two integer value? > > -- > You received this message because you are subscribed to the Google Groups > "elasticsearch" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [elasticsearch+unsubscribe@googlegroups.com](mailto:elasticsearch+unsubscribe@googlegroups.com). > To view this discussion on the web visit > [https://groups.google.com/d/msgid/elasticsearch/f073e04b-f2a1-4e5a-a7e0-ff93727f6e9f%40googlegroups.com](https://groups.google.com/d/msgid/elasticsearch/f073e04b-f2a1-4e5a-a7e0-ff93727f6e9f%40googlegroups.com)[https://groups.google.com/d/msgid/elasticsearch/f073e04b-f2a1-4e5a-a7e0-ff93727f6e9f%40googlegroups.com?utm\_medium=email&utm\_source=footer](https://groups.google.com/d/msgid/elasticsearch/f073e04b-f2a1-4e5a-a7e0-ff93727f6e9f%40googlegroups.com?utm_medium=email&utm_source=footer) > . > For more options, visit [https://groups.google.com/d/optout](https://groups.google.com/d/optout). -- Adrien Grand -- You received this message because you are subscribed to the Google Groups "elasticsearch" group. To unsubscribe from this group and stop receiving emails from it, send an email to [elasticsearch+unsubscribe@googlegroups.com](mailto:elasticsearch+unsubscribe@googlegroups.com). To view this discussion on the web visit [https://groups.google.com/d/msgid/elasticsearch/CAL6Z4j6%3D%2BZ0sTOUZpaaW6stOESDn67WSAskNXd88wiFgfp7RTQ%40mail.gmail.com](https://groups.google.com/d/msgid/elasticsearch/CAL6Z4j6%3D%2BZ0sTOUZpaaW6stOESDn67WSAskNXd88wiFgfp7RTQ%40mail.gmail.com). For more options, visit [https://groups.google.com/d/optout](https://groups.google.com/d/optout). ---
**Author:** ![Yz1](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/yz1/32/1611_2.png) [@Yz1](https://discuss.elastic.co/u/Yz1)\ **Post date:** [April 29, 2014, 4:13am UTC](https://discuss.elastic.co/t/is-it-possible-to-use-string-as--id/17236/4 "2014-04-29T04:13:46Z")
So, it seems to be mysql\_jdbc\_river's problem? Here is my sql query: "SELECT concat(fid,cmid) as \_id .... FROM forum JOIN comment ..." I set the concatenation of two integer fields to be the primary key and causes the problem I described above.. Now I am dividing two tables into separate Types within an Index and using their own integer id as the primary key. On Monday, April 28, 2014 11:00:42 PM UTC+8, Adrien Grand wrote: > Can you share the code that you used to trigger this issue? > > On Mon, Apr 28, 2014 at 4:39 PM, Yz \<[yingzh...@gmail.com](mailto:yingzh...@gmail.com) \\>wrote: > > > Through my experiment, it seems not possible to use string as primary key > > in Elasticsearch. > > If type String is used , then the \_id will be something like this: > > "\_id":"[B@fe583b" > > which uses the object address in jvm instead of the real value. > > So, is there any way to generate a composite \_id from two integer value? > > > > -- > > You received this message because you are subscribed to the Google Groups > > "elasticsearch" group. > > To unsubscribe from this group and stop receiving emails from it, send an > > email to [elasticsearc...@googlegroups.com](mailto:elasticsearc...@googlegroups.com) \. > > To view this discussion on the web visit > > [https://groups.google.com/d/msgid/elasticsearch/f073e04b-f2a1-4e5a-a7e0-ff93727f6e9f%40googlegroups.com](https://groups.google.com/d/msgid/elasticsearch/f073e04b-f2a1-4e5a-a7e0-ff93727f6e9f%40googlegroups.com)[https://groups.google.com/d/msgid/elasticsearch/f073e04b-f2a1-4e5a-a7e0-ff93727f6e9f%40googlegroups.com?utm\_medium=email&utm\_source=footer](https://groups.google.com/d/msgid/elasticsearch/f073e04b-f2a1-4e5a-a7e0-ff93727f6e9f%40googlegroups.com?utm_medium=email&utm_source=footer) > > . > > For more options, visit [https://groups.google.com/d/optout](https://groups.google.com/d/optout). > > -- > Adrien Grand -- You received this message because you are subscribed to the Google Groups "elasticsearch" group. To unsubscribe from this group and stop receiving emails from it, send an email to [elasticsearch+unsubscribe@googlegroups.com](mailto:elasticsearch+unsubscribe@googlegroups.com). To view this discussion on the web visit [https://groups.google.com/d/msgid/elasticsearch/9eaa22ea-8102-40a7-9f84-97f571ce9ef7%40googlegroups.com](https://groups.google.com/d/msgid/elasticsearch/9eaa22ea-8102-40a7-9f84-97f571ce9ef7%40googlegroups.com). For more options, visit [https://groups.google.com/d/optout](https://groups.google.com/d/optout). ---
**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\ **Post date:** [July 6, 2017, 1:32am UTC](https://discuss.elastic.co/t/is-it-possible-to-use-string-as--id/17236/5 "2017-07-06T01:32:57Z")