May 23, 2020

next.jdbc Compendium

seancorfield/next.jdbc 1.0.445

This morning I released 1.0.445 and realized it's the sixth release since I last mentioned it in a blog post, so I thought it would be helpful to summarize all of the changes made so far in 2020. 1.0.13 came out at the end of December and I decided to switch from MAJOR.MINOR.PATCH versioning to MAJOR.MINOR.COMMITS versioning since I'd already made the commitment to no breaking changes -- only fixative/accretive changes -- when the library originally moved from Alpha to Beta a year ago.

Unlike the change log and release notes which are chronological, this post is organized into fixative changes, accretive changes, and documentation improvements, with each section organized by functionality or by database as appropriate.

Bug Fixes

  • next.jdbc.result-set
    • Fixed an edge case in how qualified column names are constructed when either the table name is unavailable or the :qualifier-fn results nil or an empty string.
    • Fixed how :qualifier-fn is used when the table name is unavailable so that :qualifier-fn (constantly "qual") works the same way as's :qualifier "qual" option, which makes migration easier, as well as making use of :qualifier-fn more consistent.
    • Improved performance of some result set building code (poor performance is a bug!).


  • next.jdbc/plan
    • Added InspectableMapifiedResultSet protocol that provides "meta" information access from the abstract row that is passed into the reducing function used on the IReduceInit produced by plan. Currently, this exposes the current row-number (from the underlying ResultSet) and the column-names -- a vector of column name keywords, in "natural" order based on the SQL query, produced by the builder function passed into plan. These functions are only available from plan (or a datafiable-row produced from plan) -- they are not available on the results of execute! or execute-one! -- and additional functions will probably be added over time.
    • Use of plan with array-based builders has been made easier by adding support for numeric Associative keys and Indexed access (nth) to read column values by index, instead of by label.
  • next.jdbc/with-transaction
    • If you call this with an existing Connection, it is mutated to set up and commit (or rollback) the transaction. This made concurrent execution unpredictable so this is now synchronized via locking. It is recommended to use with-transaction on a DataSource anyway, but this makes the Connection case more predictable.
  • next.jdbc.connection
    • Improved the error messages when an unknown :dbtype is used and clarified how to use :classname.
    • Added component function for built-in support of the Component library when creating a connection pooled datasource. Note that Component is not a dependency so you can simply ignore this feature if you don't use Component.
    • The result of calling get-datasource on a db-spec hash map now supports .getLoginTimeout and .setLoginTimeout to match javax.sql.DataSource and improve next.jdbc's support for timeouts.
    • MariaDB is supported out of the box.
    • Add read-as-instant and read-as-local functions to extend ReadableColumn so that SQL DATE and TIMESTAMP columns can be read as Java Time types.
  • next.jdbc.specs
    • The Spec for JDBC URL strings explicitly requires that they start with jdbc: to match the behavior of the code (and the JDBC specification), which can improve error messages when you use instrument.
  • Options:
    • :return-keys now accepts both keywords and strings in the vector of keys to return (the documentation, code, and Spec were in conflict so allowing both was the safest choice).


I try to improve the documentation in each release, based on feedback via Slack and GitHub. The bullet points below are what I consider to be just the most notable improvements.

    • Promote the stable documentation on and make it clear the GitHub documentation is for changes made since the last release.
  • Getting Started
    • Make it clearer that plan requires reduce or some sort of reduction process.
    • Shows how to work with database metadata (this information was previously only mentioned in the migration guide).
  • Tips & Tricks
    • This has been split out from Friendly SQL Functions and now contains a lot more information.
    • Timeouts: Four different types of timeout are explained, along with how next.jdbc supports them.
    • MySQL: How to stream result sets; BLOB columns are returned as byte[], not java.sql.Blob.
    • PostgreSQL: How to stream result sets; Examples of how to work with SQL array types; Clarify the need for for java.util.Date conversion (this is also mentioned in Getting Started).
  • next.jdbc.prepare/execute-batch! now has an example of how to get generated keys from a batch insert.


As always, thanks to everyone who uses next.jdbc, thanks to everyone who has provided feedback (especially on the documentation), reported bugs, suggested improvements, or sent pull requests. next.jdbc wouldn't be what it is today without all that input!

See the change log for all the changes in release order and for overall documentation of the latest release.

Tags: clojure jdbc