v2.3.2 - 2026-06-11

• Fixed implementation of max_idle_age. Two bugs were found, one affecting the lwt implementation and another affecting all variants. The first issue was identified by seprov in #139.

This release only changes the caqti and caqti-lwt packages.

v2.3.1 - 2026-04-28

• Fixed phantom type definitions which could not be guaranteed to be distinct, as discovered by the OCaml 5.5 beta compiler (#136 reported by kit-ty-kate).

Only the caqti-miou package is affected.

v2.3.0 - 2026-04-09

Note that some of the new features of this release are only accessible through the still unstable caqti.template library, which will soon be stabilized as part of an upcoming Caqti 3 API. Due to adjustments to module names, switching to caqti.template will not ensure future compatibility. Instead, users are encouraged to add the new caqti.classic to their dependencies to ease migration to Caqti 3.

• Added an alias caqti.classic for the caqti library. This will be turned into a library providing compatibility with the current Caqti 2 API when Caqti 3 is released. The two APIs can be used side-by-side to allow incremental migration.
• The dialect descriptor for MariaDB in caqti.template now provides the server version.
• Added Query.parens, Query.litf, Query.vars, Row_type.fields to the caqti.template library.
• Revised the interface for creating row types to allow instantiating parametric types applicatively. Before this change, each application of a function representing a parametric type would generate a new type ID even when applied to the same type parameter argument. The key part of this interface is the Caqti_template.Constructor_type module.
• The query functions provided to request templates are now memoized, so that they are only called once per dialect. This is meant as an optimization; it's still good practise to avoid side-effects here.
• The new function Query.with_pos_of allows query generators to add source locations to the syntax tree, which will be emitted as SQL comments in the query string if the enable_query_annotations is set. This should simplify debugging when the query is assembled from different parts of the application code.
• The still unstable caqti.template library now supports multiple statements in a single request template, sent opportunistically as a single query where allowed. This is still experimental.
• Fixed package scoping of shim rules for sqlite3 (#133 by mefyl).
• Fixed the error classification for the SQLite3 driver (#132).
• Fixed reconnect after connection loss for PostgreSQL.

v2.2.4 - 2025-03-28

• Remove Stdlib qualification from caqti.blocking to restore compatibility with OCaml 4.

v2.2.3 - 2025-03-28

• Make the pool implementation shared-memory safe.

v2.2.2 - 2025-03-25

• Fix one test and comment out a failing assertion in another test, the latter awaiting solution to #126.

v2.2.1 - 2025-03-21

A few minor fixes discovered while making the 2.2.0 release:

• Restored compatibility with OCaml before 5.1 in a test code.
• Make it clear in the documentation that caqti.template is a preview.
• Fixed version constraint for lru.

v2.2.0 - 2025-03-20

Improvements:

• The sqlite3 driver now supports the refined error causes (Caqti_error.cause) for integrity constraint violations.
• There is now experimental support for Miou (#117 by Calascibetta Romain).
• The new library caqti.template provides a preview of a interface for creating and working with request templates, with a few new features and, I think, a tidier design. This is not yet suitable for production code, since it will change before the final version. Feedback is welcome.

Fixes:

• Fixed a memory leak in the fall-back implementation of the populate connection method which affects all except the postgresql drivers.

Deprecations:

• Caqti_request.query_id is deprecated and will be removed.
• Constructors of Caqti_type.t are now fully private and will be moved away and likely defined differently in the next major release.

Dependency updates:

• Prepare for upcoming mirage (#124 by Hannes Mehnert).

The following packages are updated in this release: caqti, caqti-lwt, caqti-miou, caqti-mirage, and all drivers.

v2.1.2 - 2024-09-04

Fixes:

• Improve error reporting when failing to load a driver (#115).
• Fix validation of dead connection in postgresql driver (#119 by Sam Tombury).
• Tolerate exceptions from pool resource allocators (#116 reported by Ryan Moore).
• Fix install script for the caqti.opam package to work with caqti.plugin.
• Fix the announced license exception in the caqti-driver-pgx package.

Dependency updates:

• Update to tls >= 1.0.0 for caqti-mirage (#120 by Hannes Mehnert).
• Update tls-eio to >= 0.17.4 for caqti-tls-eio (to eliminate a hack).
• Update async_kernel to >= v0.17.0 and tcpip to >= 8.1.0 (due to resolving deprecations for future compatibility).

v2.1.1 - 2024-02-19

This minor update fixes running of the test suite and packaging issues.

v2.1.0 - 2024-02-19

This release has been replaced by 2.1.1.

• There is now TLS support for PGX. The networking code (for PGX) was revised in the process, in particular the EIO variant is now buffered, which improves performance. TLS implementations are shipped as separate packages (caqti-tls*) but caqti-tls-async, caqti-tls-eio, and caqti-tls-lwt should be considered experimental and will be omitted from the OPAM release for now. On the other hand, caqti-mirage now ships with built-in TLS support for PGX.
• Connect functions now accept an optional configuration. For the time being, this is used for TLS parameters and for the optional tweaks_version argument, which is still available for backwards compatibility.
• The newly introduced Caqti_query.qprintf and associated formatters have been moved to a separate module Caqti_query_fmt (#108), to limit clashes when used in local open, and since the formatters were nominally underqualified.
• Constants of any field type can now be embedded in queries using the new Caqti_query.V constructor and associated shortcuts. This allows taking advantage of driver-specific encoders, e.g. to correctly convert a Ptime.Span.t to the representation expected by the target database system.
• Equality with type unification evidence is now available for Caqti_type.t and Caqti_type.Field.t. The equality type introduced for the purpose is compatible with Type.eq from OCaml 5.1, but will not be aliased yet. This required a backwards incompatible adjustment of the Caqti_type.Product constructor.
• Added tuples type constructors with arity up to 12.
• Added multi-statement parser (Caqti_query.angstrom_list_parser) intended for loading SQL schema files.
• The new caqti.plugin sublibrary is a drop-in replacement for the caqti-dynload package. It is based on the dune-site.plugin library. Please try it and report back if there are issues.
• Some updates to external dependencies, esp. we are now at EIO 0.12+.
• Fixed lacking details in error messages related to driver load failures.
• Fixed uncaught exceptions for PGX (#113).

v2.0.1 - 2023-08-14

Fixes:

• Upgrade Eio to 0.11.
• Update README and make a note about caqti-eio and caqti-mirage being experimental.
• Fix build and packaging issues.

This release was sponsored by the OCaml Software Foundation.

v2.0.0 - 2023-08-10

New features:

• Added driver based on the pure-OCaml PGX library (#38). However, due to lack of TLS support it is not suitable for production, unless you have a dedicated secure network.
• Added support for MirageOS. This only works for the PGX driver, since the other drivers link against external C libraries.
• Added experimental support for Eio, both pure-OCaml and Unix. The former supports PGX while the latter supports all drivers.
• Implemented single-row mode for PostgreSQL (#24), but while this avoids uncontrolled memory consumption when a large number of rows is returned, it is a lot less efficient.
• A new pool connection parameter ?max_idle_age provides removal resources from pools which have been unused for the given period.
• Printf-style function Caqti_query.qprintf for dynamic queries (GPR#103, Basile Clément).
• Added general-purpose product type to provide functionality covering both product and custom types.
• Added new tuple types t3, ..., t8 based on the new product type and deprecated tup2, tup3, tup4 which are now aliases for these.

Breaking changes:

• The minimal OCaml requirement is now 4.08.0.
• The connection functions previously found in caqti-lwt has been moved into a sublibrary caqti-lwt.unix as part of the addition of caqti-mirage, whereas shared functionality remains in caqti-lwt. The LWT connection function is therefore now found in Caqti_lwt_unix.
• Removed all deprecated functionality and a few unintended or undocumented definitions like the type Caqti_blocking.future and Caqti_driver_info.describe_has_typed_*.
• Reworked the driver API to accommodate the addition of the PGX driver and MirageOS and Eio support, and to avoid exposting internal interfaces in the main library. These modules are now found in the sublibraries caqti.platform and caqti.platform.unix, depending on their external depnedencies. They are not meant for use by applications, though this might not have fully clear previously.
• Removed constructors Custom, Unit, Tup2, Tup3, Tup4 from Caqti_type.t. They were private but could in prinicle be matched against.
• The extensibility of Caqti_type.Field.t has been dropped along with the associated functions for registering conversions. This means that there are no custom field types any more, only custom row types. The purpose of custom field types where to support non-standard types for 3rd party drivers; we should coordinate additions to the core type instead if needed.
• According to the above point, the caqti-type-calendar is reimplemented as a row type, which means the Cdate and Ctime constructors are gone.
• There are adjustments for the pretty printer for types. (The context is assumed to start at the lowest precedence, meaning parentheses around lowest-precedence expressions are dropped. Also, redacted is shown with suffix notation, allowing us to remove one precedence level.)
• Moved pool tuning parameters into a configuration object.

Fixes:

• Fixed a missing Preemptive.detach call for to_stream for Sqlite3.
• Incorrect error reporting related to type conversions were discovered by exhaustiveness checks when making field types non-extensible.

Other:

• The documentation of call now makes clear that the result must be retrieved in order to make sure the request is performed. This is made relevant by the addition of the PGX driver where request and retrieval are fused.
• Customized the top-level index and some other documentation work. Removal of private modules from the main library should also help to make the documentation more accessible.
• Added a benchmark to measure row decoding performance.
• Improved decoding performance by partially applying the type descriptor.

This release was sponsored by the OCaml Software Foundation.

v1.9.1 - 2022-09-21

This release only updates the caqti-driver-postgresql package, with the following fixes:

• PostgreSQL expects "=" in query values to be URI-encoded (#95).
• The validation logic for PostgreSQL was missing a call to consume available input, meaning that broken pooled connections were reused.

This release was sponsored by the OCaml Software Foundation.

v1.9.0 - 2022-09-06

New features:

• Allow unquoted semicolons in query strings in the new API. There are corner cases where it is needed, as reported in issue #87, and a parser which rejects semicolons are still available for loading schema files statement by statement.
• Add support for MySQL and MariaDB configuration files, as a solution to issue #86.
• Add a limit to the number of times a database connection is reused when pooling connections (#94). Thanks to Peter Mondlock for investigating resource usage server side motivating this addition.
• Provide access to the raw SQLite3 connection handle for the purpose of defining custom functions (#56).

Fixes:

• Add missing dune dependency on unix (GPR#85 by David Allsopp).
• Documentation fixes (GPR#82, GPR#83, GPR#84 by Reynir Björnsson, GPR#88 by Jonathan Duarte, and GPR#92 by Jim Tittsler).

Deprecations:

• Caqti_type.field was deprecated in favour of Caqti_type.Field.t.

Other:

• Replace deprecated core_kernel dependency with core.

This release was sponsored by the OCaml Software Foundation.

v1.8.0 - 2022-03-24

New features:

• A matchable representation of common causes of errors on the database side is now available, with limitations. It focuses on conditions which seem most likely useful to handle. At the moment we lack extended error codes from SQLite3 needed to make the cause fully precise.
• Expose the underlying error details from database client libraries. This is meant to be use as a last resort, and requires directly linking with the relevant drivers.
• A second set of request construction operators ->., ->?, ->!, and ->* were introduced after experience with converting existing code. Given the parameter and result type they return a function which constructs a request directly from a query string. Avoiding the need to compose with @:- simplifies local opens and usage with List.map etc.
• Environment variables are now expanded in the debug log when using the new request constructors introduced in 1.7.0.
• A new ?tweaks_version connection parameter has been added to control when the client is ready to adapt to changes in database session parameters or other adjustments of the interaction with specific database systems.
• Enable foreign key constraint checks for SQLite3 starting at tweaks version 1.8.

Fixes:

• Fixed debug logging to pass the correct driver info to the query callback instead of a dummy driver info which would cause a failure if unsupported.

Deprecations:

• The --> operator was renamed to -->!, with a deprecated alias, for consistency with the new ->! operator.
• The old convenience interface for creating requests has been deprecated in favour of the new infix operators and the new query template parser.
• Documented-only deprecations of Caqti_sql_io, Caqti_lwt_sql_io, and Caqti_async_sql_io have been annotated.

This release was sponsored by the OCaml Software Foundation.

v1.7.0 - 2022-02-13

New features:

• Added a new query-string parser based on Angstrom. Its main advantage is that it can be used stand-alone e.g. to load SQL schemas from files split into individual statements which can be sent to the database.
• Support passing a query environment to the connect and pool construction functions. This avoids using globals to modify the environment and facilitates e.g. targeting different database schemas with different connetions or connection pools.
• A new Caqti_query.E case was added to support the two above cases. This is a breaking change, but hopefully does not break existing code. The exception (not counting module type of) would be if the constructors are aliased along with an alias of the type. On the other hand, pattern matching should be compatible since the new constructor is only emitted by newly introduced functions.
• Added a module Caqti_request.Infix providing a new high-level API for constructing requests. It uses two-stage combinators, first to apply type arguments then to apply the query string. Apart from allowing nicer looking code, this solves the problem of switching to a the query string parser while maintaining backwards compatibility.
• Added set_statement_timeout to connection modules, used to set query timeout. It is only supported for PostgreSQL and MariaDB. (#74)
• Added with_transaction function to connection modules. This is just fail-safed wrapper around start, commit, and rollback.

Fixes:

• Fixed delayed recovery of connection pools after loosing connections to PostgreSQL. Due to a missing call to consume inputs, the pool validator did not discover that a connection was lost before it was attempted reused.
• Improved resilience against exceptions and monadic errors in callbacks and fixed in-use checking.
• Changed Sqlite3 driver to use non-linear parameters and improve error reporting when the wrong number of arguments are received (#77 & GPR#79 Reynir Björnsson).

Other changes:

• The Caqti license now uses the LGPL-3.0 Linking Exception instead of a rephrasing of the OCaml LGPL Linking Exception which was written for LGPL-2.1.
• Improved documentation, pretty-printing, logging, and exception details.
• The test suite has been switched to use Alcotest; not without some struggle due to the use of test harness and argument-dependent test suite, but the result seems like a clear improvement.

This release was sponsored by the OCaml Software Foundation.

v1.6.0 - 2021-06-10

• Set the time zone of PostgreSQL connections to UTC to mitigate an undesirable implicit conversion to the local time zone for timestamp. This issue was exposed by the specification of field types introduced in version 1.4.0. Earlier versions worked as expected, if only accidentally, since the time zone is ignored when a string is converted to a timestamp. While this change makes timestamp more usable again for storing UTC time stamps, I strongly recommend using timestamp with time zone since it's interpretation is unambiguous. The API reference is now updated with details about how the ptime OCaml type is mapped for different database systems.
• Drop specification of OCaml string as SQL text for PostgreSQL. This is due to issues with implicit conversions and function overloading when the desired type on the SQL side is char, varchar, or jsonb.
• Add Caqti_type.redact to protect sensitive information from being logged.
• Only log parameters if $CAQTI_DEBUG_PARAM is set to "true".
• When logging requests, show underlying values for custom types.
• Reject multi-row response in find_opt implementation for sqlite3.
• Tolerate Lwt promise rejections in Pool.use.

v1.5.1 - 2021-04-18

• Fix option recognition in PostgreSQL driver (GPR#67 mefyl).
• Fix option recognition in MariaDB driver and add test (Petter A. Urkedal).

v1.5.0 - 2021-04-11

• Request the full UTF-8 character for the MariaDB connection.
• Support int16 and enum types for parameters and rows.

v1.4.0 - 2021-03-11

• Fix infinite loop when deserializing an optional tuple (GPR#63 mefyl).
• Add Caqti_connect_sig.S.with_connection (GPR#61 Anton Bachin).
• Pass parameter types to PostgreSQL prepare and query functions. This avoids the need to CAST parameters on the SQL side in some cases.
• Add ?post_connect callback to connect_pool.
• Documentation fixes and improvements (Aaron L. Zeng, Anton Bachin, Petter A. Urkedal).

v1.3.0 - 2021-01-17

• Implement affected_count for sqlite backend (GPR#46 jakob).
• Add method exec_with_affected_count to Caqti_connection_sig.S (GPR#45 jakob).
• Add ?max_idle_size to pool creation functions.
• Dropped dependency on ppx_deriving due to issue with static compilation (GPR#50 Ulrik Strid).
• Pass through $<var>$ in query strings and deprecate $$.
• Log statements to be executed at debug level.
• Add COPYING.OCAML and fix license expression in opam files.
• Misc improvements to tests and documentation (GPR#51 Philippe Wang, GPR#54 Reynir Björnsson, etc.).

v1.2.4 - 2020-06-07

• Switch to TEXT format for PostgreSQL populate implementation.

v1.2.3 - 2020-06-02

• Silence PostgreSQL notifications which were printed to stderr. They can be re-enabled with a parameter on the connection URI (#33).
• Improve details in exceptions in two places.
• Fix info about connection caching for sqlite in README (#35, dgllghr).

v1.2.2 - 2019-12-19

• Update for core v0.13 (GPR#31 Xavier Clerc).

v1.2.1 - 2019-12-08

• Support TEXT literals in queries.
• Fix decoding of binary results for PostgreSQL (thanks to James Owen).
• Implement copy-mode for PostgreSQL (GPR#30 James Owen).

v1.2.0 - 2019-10-02

• Add a signature for the populate function, and add basic implementations for all drivers (GPR#28).
• Add stream for result extraction (GPR#22 Nathan Rebours).
• Use the postgres driver when postgres is specified as the URL scheme (GPR#25 James Owen).
• Documentation improvements (GPR#20 Nathan Rebours, etc.).
• Reimplemented partly ineffective prepare-cache for PostgreSQL.
• Backwards incompatible changes to the driver API.
• Backwards incompatible changes to modules marked internal but exposed due to being split across packages.
• Fix forward compatibility past OCaml 4.08 as announced by deprecations.

v1.1.0 - 2019-02-03

• Add pretty printer for requests.
• Add variance to 'a future declarations.
• Add blocking instance of API.
• Generalize $. to $<var>. in queries.
• Infer the expansion of $(<var>.) from $(<var>) if not provided.
• Fix connection recovery for PostgreSQL (issue #19, Dave Aitken).
• Fix some unhandled exceptions for PostgreSQL.
• Fix connection validation for MariaDB.

v1.0.0 - 2018-08-26

• Added Caqti_type.Std : Caqti_type_sig.Std, containing type descriptors needed for building requests, for easy inclusion in custom modules.
• Fix ptime to string conversion for PostgreSQL (monstasat).
• Support microsecond precision for MariaDB.
• Removed Caqti_type.Field.ex and renamed Caqti_type.ex to Caqti_type.any and related functions.
• Removed other deprecated definitions.
• Moved Caqti_system_sig into Caqti_driver and split up the signature to make room for future drivers on alternative platforms.

v0.11.0 - 2018-05-25

Added and improved:

• Compliance with Lwt 4.0 contributed by Brendan Long.
• Switched to the logs library for logging.
• Strengthen detection of concurrent use of connection.
• Support microsecond precision for timestamps for PostgreSQL and millisecond for Sqlite3.
• Use float for time spans in Sqlite3.
• Map the octets type to BLOBs for MariaDB and Sqlite3.
• Log recoverable errors for MariaDB and Sqlite3.

Removed:

• The v1 API is now removed.

Ecosystem:

• CI setup contributed by Brendan Long.
• Various documentation updates.

v0.10.2 - 2018-04-05

• Fix incompatibility with ppx_optcomp v0.11.0 by dropping it, since the conditionals where no longer needed.
• Restore test during opam build.
• The v1 API is now fully [@@@deprecated] and will be removed in the next major release.

v0.10.1 - 2018-02-27

• Fix a pool size counting bug when resource allocation fails. This can cause deadlock due to pool exhaustion.

v0.10.0 - 2018-02-14

• Added -linkall flags to driver libraries to fix direct linking (#9).
• Added convenience functions collect_list and rev_collect_list (#8).
• Renamed template to query and related function, leaving deprecated aliases.
• Added ptime_span field type mapping to SQL intervals.
• Be more permissive about types of data returned from MariaDB when expecting numerical results.

v0.9.0 - 2018-01-04

• Move v1 into findlib sublibraries and announce deprecation.
• Port remaining tests to v2 and fix issues in MariaDB and Sqlite3 drivers.
• Don't include password component of URIs in error messages.
• Rename io type constructor to future.
• Fix pool size limit enforcement.
• Drop error on disconnect.
• Support substitutions in request convenience functions.

v0.8.1 - 2017-12-06

• Fix start transaction for PostgreSQL v2.
• Fix dependency on ptime in caqti.opam in distribution.

v0.8.0 - 2017-12-04

• Remove most deprecations.
• Add new v2 API.
• Move away most of the v1 API, but keep deprecated aliases for the client API.

The main difference of the new API compared to the old is:

• It uses typed parameters and rows with an extensible variant for field type and a custom definable compound type.
• The connection has a call method which gives access to a result object before iterating over the returned rows.
• Error handling is done with the result type, using a collection of error types formed as polymorphic variants of records.

Notice: This version is mostly backwards compatible. New code should use v2, but v1 will be kept for now. To keep using the v1 in upcoming releases:

• Fix the new deprecations from this release.
• Link with caqti-dynload to keep using dynamic loading, or link with the needed caqti-driver-*.v1 driver libraries.
• Link with caqti.v1 instead of caqti.
• Link with caqti-lwt.v1 instead of caqti-lwt.
• Link with caqti-async.v1 instead of caqti-async.

v0.7.0 - 2017-11-03

• Remove WRAPPER and REPORT functionality.
• Remove deprecated findlib aliases.
• Renamed date and utc conversions to date_cl and utc_cl.
• Deprecate Caqti_metadata in favour of the new Caqti_driver_info.
• Move various signature to separate files, leaving deprecated aliases.

v0.6.1 - 2017-10-26

• Fixed support for lwt >= 3, but keep supporting 2.7 as well for now.
• Fixed preparation of query after reconnect to PostgreSQL.
• Fixed support for ocaml 4.03.x.
• Added Tuple.length.
• Deprecated Param.sub_types.
• Deprecated Param.other and Tuple.other.

v0.6.0 - 2017-06-05

• Split into separate packages to avoid depopts and rename findlib names accordingly.
• Use findlib to load DB drivers, and use -linkall. This hopefully solves loading issues.

v0.5.3 - 2017-05-22

• Fix handling of spaces in Sqlite3 URIs and allow setting mode.
• Split Caqti (now deprecated) into Caqti_errors and Caqti_connect.
• Update to async 0.9.0.

v0.5.2 - 2017-02-25

• Fix plugin loader to handle modernised META.

v0.5.1 - 2017-02-25 retracted

• Rename libraries to match META.

v0.5.0 - 2017-02-25 retracted

• Added MariaDB backend.
• Fixed VARCHAR for SQLite3 describe.