# Datomic Applications **URL:** https://forum.datomic.com/c/datomic-applications/17.md [Latest](https://forum.datomic.com/latest.md) · [Categories](https://forum.datomic.com/categories.md) --- ## [About the Datomic Applications category](https://forum.datomic.com/t/about-the-datomic-applications-category/101)
**Author:** [@jaret](https://forum.datomic.com/u/jaret)\ **Replies:** 0\ **Last updated:** [July 31, 2017, 4:29pm UTC](https://forum.datomic.com/t/about-the-datomic-applications-category/101 "2017-07-31T16:29:33Z")
Discussion of the design and implementation of systems and applications that use Datomic. Any troubleshooting topics should be opened in the respective Troubleshooting sub-category. This category is for advice, impleme… --- ## [Ingest historical data from some log files into datomic (maybe local) and preserving the transaction time](https://forum.datomic.com/t/ingest-historical-data-from-some-log-files-into-datomic-maybe-local-and-preserving-the-transaction-time/2483)
**Author:** [@danbunea](https://forum.datomic.com/u/danbunea)\ **Replies:** 1\ **Last updated:** [October 12, 2024, 8:40am UTC](https://forum.datomic.com/t/ingest-historical-data-from-some-log-files-into-datomic-maybe-local-and-preserving-the-transaction-time/2483 "2024-10-12T08:40:32Z")
In my new team, I notices the support team has to query the past for things that happened and this is achieved by keeping some json log files , where all the modifications (adds, updates and deletions ) are kept as diffs… --- ## [Seeing previous datum in a transaction?](https://forum.datomic.com/t/seeing-previous-datum-in-a-transaction/1784)
**Author:** [@hden](https://forum.datomic.com/u/hden)\ **Replies:** 1\ **Last updated:** [August 20, 2022, 8:22am UTC](https://forum.datomic.com/t/seeing-previous-datum-in-a-transaction/1784 "2022-08-20T08:22:43Z")
Let’s say I need to update a property of an entity base on the summary of multiple entities. Schema: \[{:db/ident :order/total, :db/valueType :db.type/bigdec, ...} {:db/ident :item/unit-price, :db/valueType :db.typ… --- ## [Unexpected median rounding](https://forum.datomic.com/t/unexpected-median-rounding/517)
**Author:** [@marcgrue](https://forum.datomic.com/u/marcgrue)\ **Replies:** 1\ **Last updated:** [August 13, 2022, 10:47am UTC](https://forum.datomic.com/t/unexpected-median-rounding/517 "2022-08-13T10:47:18Z")
According to the wiki entry on the median value it seems that the common interpretation of a median value of an even number of values is the average of the two middle values (when sorted). But I got surprised that Datom… --- ## [Node.js support for Datomic applications](https://forum.datomic.com/t/node-js-support-for-datomic-applications/2051)
**Author:** [@uhef](https://forum.datomic.com/u/uhef)\ **Replies:** 0\ **Last updated:** [February 21, 2022, 7:11pm UTC](https://forum.datomic.com/t/node-js-support-for-datomic-applications/2051 "2022-02-21T19:11:37Z")
I’ve been looking into Datomic and I think this would be an excellent database candidate for the product we are currently developing. I worked myself through the tutorial with my limited Clojure skills and I am pretty e… --- ## [When to use \`:db.type/uri\`?](https://forum.datomic.com/t/when-to-use-db-type-uri/1932)
**Author:** [@onetom](https://forum.datomic.com/u/onetom)\ **Replies:** 1\ **Last updated:** [August 24, 2021, 2:38pm UTC](https://forum.datomic.com/t/when-to-use-db-type-uri/1932 "2021-08-24T14:38:25Z")
What are the benefits and drawbacks of using the :db.type/uri value type? Would you store email addresses as URIs? (like mailto:x@y.z?) I can see the following pros: validation and encoding of the valid characters fo… --- ## [Query for mid-point of two databases](https://forum.datomic.com/t/query-for-mid-point-of-two-databases/1926)
**Author:** [@nwjsmith](https://forum.datomic.com/u/nwjsmith)\ **Replies:** 0\ **Last updated:** [August 10, 2021, 5:48pm UTC](https://forum.datomic.com/t/query-for-mid-point-of-two-databases/1926 "2021-08-10T17:48:42Z")
I’m writing a git bisect-like utility, and as part of this I’m looking to query for the transaction midway between two databases. Here is what I have so far: (d/q '\[:find (median ?t) :in $earlier $later :w… --- ## [Query result pagination](https://forum.datomic.com/t/query-result-pagination/205)
**Author:** [@zignd](https://forum.datomic.com/u/zignd)\ **Replies:** 5\ **Last updated:** [May 24, 2021, 4:26pm UTC](https://forum.datomic.com/t/query-result-pagination/205 "2021-05-24T16:26:00Z")
I have a hypothetical situation that I’d like to solve, but I can’t find the ideal answer. Suppose you have a huge data set that could be returned from a query, how do you paginate it, so that the impact on memory is min… --- ## [Best way to model the equivalent of join tables or cross reference tables in Datomic](https://forum.datomic.com/t/best-way-to-model-the-equivalent-of-join-tables-or-cross-reference-tables-in-datomic/1858)
**Author:** [@jzwolak](https://forum.datomic.com/u/jzwolak)\ **Replies:** 0\ **Last updated:** [May 13, 2021, 3:35pm UTC](https://forum.datomic.com/t/best-way-to-model-the-equivalent-of-join-tables-or-cross-reference-tables-in-datomic/1858 "2021-05-13T15:35:20Z")
We’re migrating a legacy Oracle Database application to Datomic and we’re trying to preserve as much of our data model as makes sense while updating to something that fits more with Datomic. I’m puzzling over what to do … --- ## [Duct-framwork + Ions](https://forum.datomic.com/t/duct-framwork-ions/1661)
**Author:** [@hden](https://forum.datomic.com/u/hden)\ **Replies:** 0\ **Last updated:** [October 18, 2020, 1:38pm UTC](https://forum.datomic.com/t/duct-framwork-ions/1661 "2020-10-18T13:38:53Z")
Hi all, I’ve build a series of tools to execute duct applications as a ion. Please take a look. Any suggestion are welcome. Cheers, hden --- ## [Access Restrictions](https://forum.datomic.com/t/access-restrictions/843)
**Author:** [@bhurlow](https://forum.datomic.com/u/bhurlow)\ **Replies:** 4\ **Last updated:** [July 14, 2020, 1:12pm UTC](https://forum.datomic.com/t/access-restrictions/843 "2020-07-14T13:12:51Z")
Hi Datomic Folks, How are people implementing access / security models in your Datomic apps? I’m working on a project and we’re looking into best practices around securing access to parts of our data according to domain… --- ## [Simplest way to remap HTTP Direct invoke url](https://forum.datomic.com/t/simplest-way-to-remap-http-direct-invoke-url/1336)
**Author:** [@nolan330](https://forum.datomic.com/u/nolan330)\ **Replies:** 5\ **Last updated:** [June 21, 2020, 5:11pm UTC](https://forum.datomic.com/t/simplest-way-to-remap-http-direct-invoke-url/1336 "2020-06-21T17:11:27Z")
HTTP Direct certainly needs no introduction. We’d like to expose an HTTP Direct proxy without exposing consumers to /datomic endpoint URLs. From what I’ve gathered, there could be a few ways to go about remapping /datom… --- ## [Composite index](https://forum.datomic.com/t/composite-index/1414)
**Author:** [@hden](https://forum.datomic.com/u/hden)\ **Replies:** 3\ **Last updated:** [April 18, 2020, 2:58am UTC](https://forum.datomic.com/t/composite-index/1414 "2020-04-18T02:58:46Z")
Say that I’m working on a Google Calendar-like database where people store meetings. A meeting have a start time and end time (mostly an hour or two). A meeting can occupy multiple rooms. Meetings might temporarily ove… --- ## [Parameterizing Ion configuration](https://forum.datomic.com/t/parameterizing-ion-configuration/479)
**Author:** [@markaddleman](https://forum.datomic.com/u/markaddleman)\ **Replies:** 6\ **Last updated:** [March 26, 2020, 8:25pm UTC](https://forum.datomic.com/t/parameterizing-ion-configuration/479 "2020-03-26T20:25:03Z")
How would we parameterize the configuration for ions? For example, we have multiple Datomic databases - one each developer. How would we configure a lambda to use one database or another? In our current development wo… --- ## [Location Sensitive Queries](https://forum.datomic.com/t/location-sensitive-queries/1401)
**Author:** [@lucasjordan](https://forum.datomic.com/u/lucasjordan)\ **Replies:** 0\ **Last updated:** [March 26, 2020, 7:22pm UTC](https://forum.datomic.com/t/location-sensitive-queries/1401 "2020-03-26T19:22:29Z")
I am investigating Datomic for a new application, I have followed the project for years, but have never implemented a production system with any flavor of Datomic. I am trying to evaluate support for location based sear… --- ## [Datomic with Terraform](https://forum.datomic.com/t/datomic-with-terraform/1295)
**Author:** [@jdhollis](https://forum.datomic.com/u/jdhollis)\ **Replies:** 2\ **Last updated:** [December 28, 2019, 4:47pm UTC](https://forum.datomic.com/t/datomic-with-terraform/1295 "2019-12-28T16:47:12Z")
Hi, all. I probably should have posted this here immediately after the Conj, but I’ve published a post covering the content of my talk on my site: Datomic with Terraform If you want to dive straight into the Terraform,… --- ## [The single transactor and write performance](https://forum.datomic.com/t/the-single-transactor-and-write-performance/275)
**Author:** [@jamesvickers](https://forum.datomic.com/u/jamesvickers)\ **Replies:** 4\ **Last updated:** [October 16, 2019, 3:46pm UTC](https://forum.datomic.com/t/the-single-transactor-and-write-performance/275 "2019-10-16T15:46:34Z")
Probably like some other people, I am curious how the architecture of a single Transactor affects performance. Does the Transactor have any multi-threaded aspects (like accepting data from Peers in parallel)? Can someo… --- ## [Dynamic queueing in Datomic](https://forum.datomic.com/t/dynamic-queueing-in-datomic/1015)
**Author:** [@lsnape](https://forum.datomic.com/u/lsnape)\ **Replies:** 4\ **Last updated:** [June 13, 2019, 9:36am UTC](https://forum.datomic.com/t/dynamic-queueing-in-datomic/1015 "2019-06-13T09:36:37Z")
I’m evaluating Datomic Cloud as an alternative to a relational database we’re using in one of our applications. The current approach is presenting us with challenges that I think Datomic will solve quite neatly. At th… --- ## [Ions push/deployments automation issues](https://forum.datomic.com/t/ions-push-deployments-automation-issues/715)
**Author:** [@adriffaud](https://forum.datomic.com/u/adriffaud)\ **Replies:** 4\ **Last updated:** [May 18, 2019, 9:56am UTC](https://forum.datomic.com/t/ions-push-deployments-automation-issues/715 "2019-05-18T09:56:05Z")
Hi guys, Trying to automate ions push/deployment using CodeBuild, I get stuck with an S3 error: {:deploy-status ERROR, :message VPC endpoints do not support cross-region requests (Service: Amazon S3; Status Code: 403; … --- ## [Reading files from the resource path](https://forum.datomic.com/t/reading-files-from-the-resource-path/868)
**Author:** [@hadils](https://forum.datomic.com/u/hadils)\ **Replies:** 3\ **Last updated:** [March 4, 2019, 7:45pm UTC](https://forum.datomic.com/t/reading-files-from-the-resource-path/868 "2019-03-04T19:45:46Z")
I am a newbie with Datomic, but successfully got my Ion code to deploy and execute. I am trying to read json and edn files from the resource path, but I don’t know how to do it. Thanks for any help with this, Hadil --- ## [Attribute naming conventions](https://forum.datomic.com/t/attribute-naming-conventions/835)
**Author:** [@tomc](https://forum.datomic.com/u/tomc)\ **Replies:** 10\ **Last updated:** [March 1, 2019, 5:40pm UTC](https://forum.datomic.com/t/attribute-naming-conventions/835 "2019-03-01T17:40:59Z")
There doesn’t seem to be much available online regarding datomic attribute naming conventions. I started thinking about this because I realized I was using - and . inconsistently in my attribute names. I’m hoping to find… --- ## [Data non-retention and redaction](https://forum.datomic.com/t/data-non-retention-and-redaction/665)
**Author:** [@psagers](https://forum.datomic.com/u/psagers)\ **Replies:** 2\ **Last updated:** [February 5, 2019, 6:34pm UTC](https://forum.datomic.com/t/data-non-retention-and-redaction/665 "2019-02-05T18:34:19Z")
I’m currently evaluating Datomic for some upcoming projects and while it seems like an excellent fit in many regards, I am getting a bit hung up on the indelibility. While there are many contexts in which this sounds lik… --- ## [Conj in a rule fails on the transactor](https://forum.datomic.com/t/conj-in-a-rule-fails-on-the-transactor/413)
**Author:** [@benfle](https://forum.datomic.com/u/benfle)\ **Replies:** 3\ **Last updated:** [January 14, 2019, 4:53pm UTC](https://forum.datomic.com/t/conj-in-a-rule-fails-on-the-transactor/413 "2019-01-14T16:53:39Z")
Hi everyone, I have a hard time understanding why the following rule sometimes fail with a ClassCastException on the conj. Apparently ?parent-path is a Java array and not a IPersistentCollection. This only happens in t… --- ## [Data science with Datomic](https://forum.datomic.com/t/data-science-with-datomic/779)
**Author:** [@Aitor](https://forum.datomic.com/u/Aitor)\ **Replies:** 0\ **Last updated:** [January 6, 2019, 11:48am UTC](https://forum.datomic.com/t/data-science-with-datomic/779 "2019-01-06T11:48:42Z")
Hello! Firstly, I’m new to Datomic and in the forum, so nice to meet you all :slight\_smile: We’ve been asked to make some data analysis over data that is stored in Datomic. Our aim is to analyze the stored data and crea… --- ## [Datomic time queries](https://forum.datomic.com/t/datomic-time-queries/693)
**Author:** [@Nikaustr](https://forum.datomic.com/u/Nikaustr)\ **Replies:** 2\ **Last updated:** [November 15, 2018, 11:45pm UTC](https://forum.datomic.com/t/datomic-time-queries/693 "2018-11-15T23:45:24Z")
Hi guys, Imagine having the following Datomic schema: \[{:db/ident :group/name :db/valueType :db.type/string :db/cardinality :db.cardinality/one :db/unique :db.unique/value :db/… --- ## [Ions \`datomic.ion.dev\` documentation?](https://forum.datomic.com/t/ions-datomic-ion-dev-documentation/627)
**Author:** [@heyzk](https://forum.datomic.com/u/heyzk)\ **Replies:** 2\ **Last updated:** [October 11, 2018, 1:13pm UTC](https://forum.datomic.com/t/ions-datomic-ion-dev-documentation/627 "2018-10-11T13:13:19Z")
I’m trying automate deployment for an ion app, is there any documentation available online for the datomic.ion.dev namespace? --- ## [A few thoughts on Tiago's excellent screencast](https://forum.datomic.com/t/a-few-thoughts-on-tiagos-excellent-screencast/532)
**Author:** [@stu](https://forum.datomic.com/u/stu)\ **Replies:** 0\ **Last updated:** [July 11, 2018, 8:07pm UTC](https://forum.datomic.com/t/a-few-thoughts-on-tiagos-excellent-screencast/532 "2018-07-11T20:07:34Z")
While we were working on today’s release, Tiago released an excellent screencast Datomic Ions Hello World in 25 Minutes. Since today’s enhancements directly impact the initial experience, I wanted to call attention to a… --- ## [Add attribute check to db call](https://forum.datomic.com/t/add-attribute-check-to-db-call/414)
**Author:** [@pcolliander](https://forum.datomic.com/u/pcolliander)\ **Replies:** 5\ **Last updated:** [April 26, 2018, 5:13pm UTC](https://forum.datomic.com/t/add-attribute-check-to-db-call/414 "2018-04-26T17:13:26Z")
In my application I was using a transaction function like this to delete an entity: (d/transact conn \[\[:db.fn/retractEntity id\]\]). I decided to add a check that the given entity also has the same user ID attribute that… --- ## [Handling ordered lists](https://forum.datomic.com/t/handling-ordered-lists/305)
**Author:** [@dave.liepmann](https://forum.datomic.com/u/dave.liepmann)\ **Replies:** 3\ **Last updated:** [April 24, 2018, 3:33pm UTC](https://forum.datomic.com/t/handling-ordered-lists/305 "2018-04-24T15:33:35Z")
As we all know, Datomic’s cardinality/many relationships are sets. To enforce a sequential order on a many attribute, one must manually implement a linked list or a position attribute, or serialize the list and store tha… --- ## [Nano-second time resolution](https://forum.datomic.com/t/nano-second-time-resolution/387)
**Author:** [@ranjanprakash](https://forum.datomic.com/u/ranjanprakash)\ **Replies:** 2\ **Last updated:** [April 5, 2018, 5:46pm UTC](https://forum.datomic.com/t/nano-second-time-resolution/387 "2018-04-05T17:46:23Z")
I have timestamp field with 100 nano seconds resolution. As 'instant’s can represent only in milli seconds, potentially 10K events can get bucketed in the same ‘instant’. One way to order and filer them correctly is to s… [Next page](https://forum.datomic.com/c/datomic-applications/17.md?page=1)