is there a way to use datomic/entity and add additional computed data on the “map”? We noticed that assoc throws. We can merge a new map with the attributes with the entity but then we lose the laziness that datomic/entity provides.

@hmaurer @dominicm @benha thanks for the tips regarding the invitation code generation

@mkvlr you could reify IAssoc to allow local assoc calls, but pass through gets to underlying EntityMap

but be aware that this does not transact the new data to datomic

which is likely to cause confusion

sure, I’m aware it doesn’t transact

any other best practices to add computed data to an entity? Not put it on the entity at all but use another thing?

@mkvlr silly question, but do you really need to keep the map lazy?

and do you need to add computed data deep inside the map, or only at the top level?

@hmaurer only at the top level. I’m new to datomic, so I’m asking for best practices

what if I touch the entity, will I still be able to lazily load relations reachable from it?

mmh I am not sure, but let’s try it

just a sec

mmh no, it looks like touching loads the whole thing

> Touches all of the attributes of the entity, including any component entities recursively.

for components at least

I am new to Datomic too so I am just trying things out, but it looks like (into {} your-entity) will return a PersistentArrayMap at the top level, but leave EntityMaps for nested entities (which are lazy)

@mkvlr ^

@hmaurer thanks! that’s great then, I’ll just touch 🙏

@favila yes, I realized my mistake, thanks!

@favila do you know if datomic will attempt to optimise queries, and if yes, how? e.g. are clauses re-ordered on datalog queries?

Datomic does some optimizations, but clause reordering is not one of them. I think they may never add that optimization for philosophical reasons

is anyone familiar with this stack trace, and what the cause might be? I see it when I transact my schema using datomic.api

11:16:24 ERROR         nREPL-worker-0 core.client                        AMQ214016: Failed to create netty connection
java.nio.channels.UnresolvedAddressException
        at sun.nio.ch.Net.checkAddress(Net.java:101)
        at sun.nio.ch.SocketChannelImpl.connect(SocketChannelImpl.java:622)
        at io.netty.channel.socket.nio.NioSocketChannel.doConnect(NioSocketChannel.java:208)
        at io.netty.channel.nio.AbstractNioChannel$AbstractNioUnsafe.connect(AbstractNioChannel.java:203)
        at io.netty.channel.DefaultChannelPipeline$HeadContext.connect(DefaultChannelPipeline.java:1226)
        at io.netty.channel.AbstractChannelHandlerContext.invokeConnect(AbstractChannelHandlerContext.java:549)
        at io.netty.channel.AbstractChannelHandlerContext.connect(AbstractChannelHandlerContext.java:534)
        at io.netty.handler.ssl.SslHandler.connect(SslHandler.java:438)
        at io.netty.channel.AbstractChannelHandlerContext.invokeConnect(AbstractChannelHandlerContext.java:549)
        at io.netty.channel.AbstractChannelHandlerContext.connect(AbstractChannelHandlerContext.java:534)
        at io.netty.channel.ChannelDuplexHandler.connect(ChannelDuplexHandler.java:50)
        at io.netty.channel.AbstractChannelHandlerContext.invokeConnect(AbstractChannelHandlerContext.java:549)
        at io.netty.channel.AbstractChannelHandlerContext.connect(AbstractChannelHandlerContext.java:534)
        at io.netty.channel.AbstractChannelHandlerContext.connect(AbstractChannelHandlerContext.java:516)
        at io.netty.channel.DefaultChannelPipeline.connect(DefaultChannelPipeline.java:970)
        at io.netty.channel.AbstractChannel.connect(AbstractChannel.java:215)
        at io.netty.bootstrap.Bootstrap$2.run(Bootstrap.java:166)
        at io.netty.util.concurrent.SingleThreadEventExecutor.runAllTasks(SingleThreadEventExecutor.java:408)
        at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:402)
        at io.netty.util.concurrent.SingleThreadEventExecutor$2.run(SingleThreadEventExecutor.java:140)
        at java.lang.Thread.run(Thread.java:745)

You sure it is datomic.api and not datomic.client?

looks like it can't resolve an address

hostname somewhere is wrong

yes, datomic.api. it's coming from ActiveMQ, there should be no hostname resolution required for the transaction (uri is DDB which looks up the transactor IP in Dynamo)

what is in transactor host= and alt-host= ?

ah, alt-host has some garbage, thanks for the tip

does anyone know if the :string type for an attribute has any sort of character limit? I cannot seem to find anything in the documentation that would suggest there is. Thanks

@phillipc AFAIK no intrinsic limit. you will probably run into platform limits first (e.g. string too long for java or fressian)

but it's not a good idea to put big values into a datomic db

consider writing a uuid-named file to a blob store (e.g. s3) and storing the reference in the db as the value

I doubt it will be large enough for a blob, I'm just converting some sql data stores and was making sure that :string could handle it Thank you for the quick response!

oh, yeah it will handle that fine