I have just transferred my Postgis database onto an RDS server, and there is a bit of a performance hit when using the Identify tool in QGIS (3) compared to localhost. I presume this is mostly network latency, however I wonder if it could be not picking up the spatial index or something. There is a GIST index set up on the table, but identify queries are still taking around 10 seconds, which seems too long, considering rendering is considerably quicker than that.

I did look at the code here and it does seem on a quick glance that things are being done client side (and presumably calling back to the server for the data hence the delay) where it would be quicker to call the server and ask it to identify the object using the indexes.

Are there any options I can tweak that anyone knows of or is this one for the QGIS developers?

  • what is the ping (lag) from your ip to the RDS server? if there is IIS involved it needs to wake up [cold start]. There are settings to keep alive but cpu will go up a little. – Mapperz Feb 28 '18 at 19:18
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    You've misinterpreted the code - qgis calculates a small region around the click location and then sends that to the underlying data provider. So postgis indices will be used if they are available. – ndawson Feb 28 '18 at 20:29

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