I've just realized that ES has a _/_template and a _/_index_template.
What are they for?
I was using code:
PutIndexTemplateRequest ngramTemplate = new PutIndexTemplateRequest("ngram-template")
.patterns(Arrays.asList("resourcetable-*", "termconcept-*"))
.settings(Settings.builder().put("index.max_ngram_diff", 50));
I didn't understand why my ngram-template didn't appear on _/_index_template.
After that, I was looking on _/_template.....
Which is the difference between them?
Elasticsearch switched from _template to _index_template in version 7.8.
_template is deprecated in 7.8 but still usable. if an indices match both lagacy template (_template) and Composable template (_index_template), elasticsearch will use Composable template.
the main difference betwean legacy and composable template is that legacy template is static and if you want change a field in all templates you must edit all templates but new _index_template is modular and for changing a setting in all templates you only need to change one component.