ETAG support

Read more about How ETAG works!

Search API & ETAG

Search response contains etag information in the etag header and in meta.versionId. You can cache result and use If-None-Match header or _etag parameter to get the latest data from the server or a response with 304 if nothing has been changed.

GET /Patient
Accept: text/yaml

# resp
status: 200
headers:
  ETag: '999'
body:
  meta: {versionId: '999'}
  ....

# you can cache response and versionId

# get 
GET /Patient?_etag=999 # laset versionId
Accept: text/yaml
If-None-Match: 999

# resp
status: 304

# if etag is old you will get result
GET /Patient?_etag=99
Accept: text/yaml

# resp
status: 200
body:
  meta: {versionId: '999'}

ETag Cache

All ETag values are cached to make ETag queries efficient. If you somehow made this cache invalid, you can reset Aidbox ETag cache by DELETE /$etags-cache or DELETE /Patient/$etags-cache.

Aidbox ETags mechanisms is based on txid column of resource table in database! If you update resources in database, don't forget to update the txid column and reset cache. UPDATE resource SET txid = nextval('transaction_id_seq')

ETag Cache performance

To build a cache for a specific resourceType ETag Aidbox runs a query to get the max value of the txid column. To make this operation efficient, it's recommended to build an index on the txid column for tables where ETag will be used.

Use query:

CREATE INDEX IF NOT EXISTS <resourceType>_txid_btree ON <resourceType> using btree(txid);

CREATE INDEX IF NOT EXISTS <resourceType>_history_txid_btree ON <resourceType>_history using btree(txid);

replace with table name, for example CREATE INDEX IF NOT EXISTS patient_txid_btree ON patient using btree(txid); CREATE INDEX IF NOT EXISTS patient_history_txid_btree ON patient_history using btree(txid);