cargo-pgx

cargo-pgx is a Cargo subcommand for managing pgx-based Postgres extensions.

You'll want to use cargo pgx during your extension development process. It automates the process of creating new Rust crate projects, auto-generating the SQL schema for your extension, installing your extension locally for testing with Postgres, and running your test suite against one or more versions of Postgres.

A video walkthrough of its abilities can be found here: https://www.twitch.tv/videos/684087991

Installing

Install via crates.io:

shell script $ cargo install --locked cargo-pgx

As new versions of pgx are released, you'll want to make sure you run this command again to update it. You should also reinstall cargo-pgx whenever you update rustc so that the same compiler is used to build cargo-pgx and your Postgres extensions. You can force cargo to reinstall an existing crate by passing --force.

Usage

```shell script $ cargo pgx --help cargo-pgx 0.5.0 ZomboDB, LLC zombodb@gmail.com Cargo subcommand for 'pgx' to make Postgres extension development easy

USAGE: cargo pgx [OPTIONS]

OPTIONS: -h, --help Print help information -v, --verbose Enable info logs, -vv for debug, -vvv for trace -V, --version Print version information

SUBCOMMANDS: connect Connect, via psql, to a Postgres instance get Get a property from the extension control file help Print this message or the help of the given subcommand(s) init Initialize pgx development environment for the first time install Install the extension from the current crate to the Postgres specified by whatever pg_config is currently on your $PATH new Create a new extension crate package Create an installation package directory run Compile/install extension to a pgx-managed Postgres instance and start psql schema Generate extension schema files start Start a pgx-managed Postgres instance status Is a pgx-managed Postgres instance running? stop Stop a pgx-managed Postgres instance test Run the test suite for this crate ```

Environment Variables

PGX_HOME - If set, overrides pgx's default directory of ~/.pgx/
PGX_BUILD_FLAGS - If set during cargo pgx run/test/install, these additional flags are passed to cargo build while building the extension
PGX_BUILD_VERBOSE - Set to true to enable verbose "build.rs" output -- useful for debugging build issues
HTTPS_PROXY - If set during cargo pgx init, it will download the Postgres sources using these proxy settings. For more details refer to the env_proxy crate documentation.

First Time Initialization

shell script $ cargo pgx init Discovered Postgres v15.0, v14.5, v13.8, v12.12, v11.17 Downloading Postgres v15.0 from https://ftp.postgresql.org/pub/source/v15.0/postgresql-15.0.tar.bz2 Downloading Postgres v11.17 from https://ftp.postgresql.org/pub/source/v11.17/postgresql-11.17.tar.bz2 Downloading Postgres v12.12 from https://ftp.postgresql.org/pub/source/v12.12/postgresql-12.12.tar.bz2 Downloading Postgres v13.8 from https://ftp.postgresql.org/pub/source/v13.8/postgresql-13.8.tar.bz2 Downloading Postgres v14.5 from https://ftp.postgresql.org/pub/source/v14.5/postgresql-14.5.tar.bz2 Removing /home/yourself/.pgx/11.17 Untarring Postgres v11.17 to /home/yourself/.pgx/11.17 Removing /home/yourself/.pgx/14.5 Removing /home/yourself/.pgx/12.12 Untarring Postgres v14.5 to /home/yourself/.pgx/14.5 Untarring Postgres v12.12 to /home/yourself/.pgx/12.12 Removing /home/yourself/.pgx/15.0 Removing /home/yourself/.pgx/13.8 Untarring Postgres v15.0 to /home/yourself/.pgx/15.0 Untarring Postgres v13.8 to /home/yourself/.pgx/13.8 Configuring Postgres v11.17 Configuring Postgres v12.12 Configuring Postgres v14.5 Configuring Postgres v13.8 Configuring Postgres v15.0 Compiling Postgres v11.17 Compiling Postgres v12.12 Compiling Postgres v13.8 Compiling Postgres v14.5 Compiling Postgres v15.0 Installing Postgres v11.17 to /home/yourself/.pgx/11.17/pgx-install Installing Postgres v12.12 to /home/yourself/.pgx/12.12/pgx-install Installing Postgres v13.8 to /home/yourself/.pgx/13.8/pgx-install Installing Postgres v14.5 to /home/yourself/.pgx/14.5/pgx-install Installing Postgres v15.0 to /home/yourself/.pgx/15.0/pgx-install Validating /home/yourself/.pgx/11.17/pgx-install/bin/pg_config Validating /home/yourself/.pgx/12.12/pgx-install/bin/pg_config Validating /home/yourself/.pgx/13.8/pgx-install/bin/pg_config Validating /home/yourself/.pgx/14.5/pgx-install/bin/pg_config Validating /home/yourself/.pgx/15.0/pgx-install/bin/pg_config

cargo pgx init is required to be run once to properly configure the pgx development environment.

As shown by the screenshot above, it downloads the latest versions of Postgres v11, v12, v13, v14, v15, configures them, compiles them, and installs them to ~/.pgx/. Other pgx commands such as run and test will fully manage and otherwise use these Postgres installations for you.

pgx is designed to support multiple Postgres versions in such a way that during development, you'll know if you're trying to use a Postgres API that isn't common across all versions. It's also designed to make testing your extension against these versions easy. This is why it requires you to have all fully compiled and installed versions of Postgres during development.

In cases when default ports pgx uses to run PostgreSQL within are not available, one can specify custom values for these during initialization using --base-port and --base-testing-port options. One of the use cases for this is using multiple installations of pgx (using $PGX_HOME variable) when developing multiple extensions at the same time. These values can be later changed in $PGX_HOME/config.toml.

If you want to use your operating system's package manager to install Postgres, cargo pgx init has optional arguments that allow you to specify where they're installed (see below).

What you're telling cargo pgx init is the full path to pg_config for each version.

For any version you specify, cargo pgx init will forego downloading/compiling/installing it. pgx will then use that locally-installed version just as it uses any version it downloads/compiles/installs itself.

However, if the "path to pg_config" is the literal string download, then pgx will download and compile that version of Postgres for you.

When the various --pgXX options are specified, these are the only versions of Postgres that pgx will manage for you.

You'll also want to make sure you have the "postgresql-server-dev" package installed for each version you want to manage yourself.

Once complete, cargo pgx init also creates a configuration file (~/.pgx/config.toml) that describes where to find each version's pg_config tool.

If a new minor Postgres version is released in the future you can simply run cargo pgx init [args] again, and your local version will be updated, preserving all existing databases and configuration.

```shell script cargo-pgx-init 0.5.0 ZomboDB, LLC zombodb@gmail.com Initialize pgx development environment for the first time

USAGE: cargo pgx init [OPTIONS]

OPTIONS: --base-port Base port number

    --base-testing-port <BASE_TESTING_PORT>
        Base testing port number

-h, --help           Print help information
    --pg11 <PG11>    If installed locally, the path to PG11's `pgconfig` tool, or `download` to
                     have pgx download/compile/install it [env: PG11_PG_CONFIG=]
    --pg12 <PG12>    If installed locally, the path to PG12's `pgconfig` tool, or `download` to
                     have pgx download/compile/install it [env: PG12_PG_CONFIG=]
    --pg13 <PG13>    If installed locally, the path to PG13's `pgconfig` tool, or `download` to
                     have pgx download/compile/install it [env: PG13_PG_CONFIG=]
    --pg14 <PG14>    If installed locally, the path to PG14's `pgconfig` tool, or `download` to
                     have pgx download/compile/install it [env: PG14_PG_CONFIG=]
    --pg15 <PG15>    If installed locally, the path to PG14's `pgconfig` tool, or `download` to
                     have pgx download/compile/install it [env: PG15_PG_CONFIG=]
-v, --verbose        Enable info logs, -vv for debug, -vvv for trace
-V, --version        Print version information

```

Creating a new Extension

rust $ cargo pgx new example $ ls example/ Cargo.toml example.control sql src

cargo pgx new <extname> is an easy way to get started creating a new extension. It's similar to cargo new <name>, but does the additional things necessary to support building a Rust Postgres extension.

If you'd like to create a "background worker" instead, specify the --bgworker argument.

cargo pgx new does not initialize the directory as a git repo, but it does create a .gitignore file in case you decide to do so.

Workspace users: cargo pgx new $NAME will create a $NAME/.cargo/config, you should move this into your workspace root as .cargo./config.

If you don't, you may experience unnecessary rebuilds using tools like Rust-Analyzer, as it will use the wrong rustflags option.

```shell script $ cargo pgx new --help cargo-pgx-new 0.5.0 ZomboDB, LLC zombodb@gmail.com Create a new extension crate

USAGE: cargo pgx new [OPTIONS]

ARGS: The name of the extension

OPTIONS: -b, --bgworker Create a background worker template -h, --help Print help information -v, --verbose Enable info logs, -vv for debug, -vvv for trace -V, --version Print version information ```

Managing Your Postgres Installations

```shell script $ cargo pgx status all Postgres v10 is stopped Postgres v11 is stopped Postgres v12 is stopped Postgres v13 is stopped Postgres v14 is stopped

$ cargo pgx start all Starting Postgres v10 on port 28810 Starting Postgres v11 on port 28811 Starting Postgres v12 on port 28812 Starting Postgres v13 on port 28813 Starting Postgres v14 on port 28814

$ cargo pgx status all Postgres v10 is running Postgres v11 is running Postgres v12 is running Postgres v13 is running Postgres v14 is running

$ cargo pgx stop all Stopping Postgres v10 Stopping Postgres v11 Stopping Postgres v12 Stopping Postgres v13 Stopping Postgres v14 ```

cargo pgx has three commands for managing each Postgres installation: start, stop, and status. Additionally, cargo pgx run (see below) will automatically start its target Postgres instance if not already running.

When starting a Postgres instance, pgx starts it on port 28800 + PG_MAJOR_VERSION, so Postgres 11 runs on 28811, 12 on 28812, etc. Additionally, the first time any of these are started, it'll automaticaly initialize a PGDATA directory in ~/.pgx/data-[11 | 12 | 13 | 14 | 15]. Doing so allows pgx to manage either Postgres versions it installed or ones already on your computer, and to make sure that in the latter case, pgx managed versions don't interfere with what might already be running.

pgx doesn't tear down these instances. While they're stored in a hidden directory in your home directory, pgx considers these important and permanent database installations.

Once started, you can connect to them using psql (if you have it on your $PATH) like so: psql -p 28812. However, you probably just want the cargo pgx run command.

Compiling and Running Your Extension

`shell script $ cargo pgx run pg13 building extension with features "cargo" "build" "--message-format=json-render-diagnostics" Finished dev [unoptimized + debuginfo] target(s) in 0.06s

installing extension Copying control file to /home/ana/.pgx/13.5/pgx-install/share/postgresql/extension/strings.control Copying shared library to /home/ana/.pgx/13.5/pgx-install/lib/postgresql/strings.so Building for SQL generation with features `` Finished dev [unoptimized + debuginfo] target(s) in 0.07s Discovering SQL entities Discovered 6 SQL entities: 0 schemas (0 unique), 6 functions, 0 types, 0 enums, 0 sqls, 0 ords, 0 hashes, 0 aggregates Writing SQL entities to /home/ana/.pgx/13.5/pgx-install/share/postgresql/extension/strings--0.1.0.sql Finished installing strings Starting Postgres v13 on port 28813 Re-using existing database strings psql (13.5) Type "help" for help.

strings=# select strings.to_lowercase('PGX');

to_lowercase

pgx (1 row) ```

cargo pgx run <pg11 | pg12 | pg13 | pg14 | pg15> is the primary interface into compiling and interactively testing/using your extension during development.

The very first time you execute cargo pgx run pgXX, it needs to compile not only your extension, but pgx itself, along with all its dependencies. Depending on your computer, this could take a bit of time (pgx is nearly 200k lines of Rust when counting the generated bindings for Postgres). Afterwards, however (as seen in the above screenshot), it's fairly fast.

cargo pgx run compiles your extension, installs it to the specified Postgres installation as described by its pg_config tool, starts that Postgres instance using the same process as cargo pgx start pgXX, and drops you into a psql shell connected to a database, by default, named after your extension. From there, it's up to you to create your extension and use it.

This is also the stage where pgx automatically generates the SQL schema for your extension via the sql-generator binary.

When you exit psql, the Postgres instance continues to run in the background.

For Postgres installations which are already on your computer, cargo pgx run will need write permissions to the directories described by pg_config --pkglibdir and pg_config --sharedir. It's up to you to decide how to make that happen. While a single Postgres installation can be started multiple times on different ports and different data directories, it does not support multiple "extension library directories".

```shell script $ cargo pgx run --help cargo-pgx-run 0.5.0 ZomboDB, LLC zombodb@gmail.com Compile/install extension to a pgx-managed Postgres instance and start psql

USAGE: cargo pgx run [OPTIONS] [ARGS]

ARGS: Do you want to run against Postgres pg11, pg12, pg13, pg14, pg15? [env: PG_VERSION=] The database to connect to (and create if the first time). Defaults to a database with the same name as the current extension name

OPTIONS: --all-features Activate all available features

    --features <FEATURES>
        Space-separated list of features to activate

-h, --help
        Print help information

    --manifest-path <MANIFEST_PATH>
        Path to Cargo.toml

    --no-default-features
        Do not activate the `default` feature

-p, --package <PACKAGE>
        Package to build (see `cargo help pkgid`)

    --pgcli
        Use an existing `pgcli` on the $PATH [env: PGX_PGCLI=]

    --profile <PROFILE>
        Specific profile to use (conflicts with `--release`)

-r, --release
        Compile for release mode (default is debug)

-v, --verbose
        Enable info logs, -vv for debug, -vvv for trace

-V, --version
        Print version information

```

Connect to a Database

```shell script $ cargo pgx connect Re-using existing database strings psql (13.5) Type "help" for help.

strings=# select strings.to_lowercase('PGX');

to_lowercase

pgx (1 row)

strings=# ```

If you'd simply like to connect to a managed version of Postgres without re-compiling and installing your extension, use cargo pgx connect <pg11 | pg12 | pg13 | pg14 | pg15>.

This command will use the default database named for your extension, or you can specify another database name as the final argument.

If the specified database doesn't exist, cargo pgx connect will create it. Similarly, if the specified version of Postgres isn't running, it'll be automatically started.

```shell script cargo-pgx-connect 0.5. ZomboDB, LLC zombodb@gmail.com Connect, via psql, to a Postgres instance

USAGE: cargo pgx connect [OPTIONS] [ARGS]

OPTIONS: -h, --help Print help information

    --manifest-path <MANIFEST_PATH>
        Path to Cargo.toml

-p, --package <PACKAGE>
        Package to determine default `pg_version` with (see `cargo help pkgid`)

    --pgcli
        Use an existing `pgcli` on the $PATH [env: PGX_PGCLI=]

-v, --verbose
        Enable info logs, -vv for debug, -vvv for trace

-V, --version
        Print version information

```

Installing Your Extension Locally

`shell script $ cargo pgx install building extension with features "cargo" "build" "--message-format=json-render-diagnostics" Finished dev [unoptimized + debuginfo] target(s) in 0.06s

installing extension Copying control file to /usr/share/postgresql/13/extension/strings.control Copying shared library to /usr/lib/postgresql/13/lib/strings.so Building for SQL generation with features `` Finished dev [unoptimized + debuginfo] target(s) in 0.06s Discovering SQL entities Discovered 6 SQL entities: 0 schemas (0 unique), 6 functions, 0 types, 0 enums, 0 sqls, 0 ords, 0 hashes, 0 aggregates Writing SQL entities to /usr/share/postgresql/13/extension/strings--0.1.0.sql Finished installing strings ```

If for some reason cargo pgx run <PG_VERSION> isn't your style, you can use cargo pgx install to install your extension to the Postgres installation described by the pg_config tool currently on your $PATH.

You'll need write permissions to the directories described by pg_config --pkglibdir and pg_config --sharedir.

By default, cargo pgx install builds your extension in debug mode. Specifying --release changes that.

``shell script $ cargo pgx install --help cargo-pgx-install 0.5.0 ZomboDB, LLC <zombodb@gmail.com> Install the extension from the current crate to the Postgres specified by whateverpg_config` is currently on your $PATH

USAGE: cargo pgx install [OPTIONS]

OPTIONS: --all-features Activate all available features

-c, --pg-config <PG_CONFIG>
        The `pg_config` path (default is first in $PATH)

    --features <FEATURES>
        Space-separated list of features to activate

-h, --help
        Print help information

    --manifest-path <MANIFEST_PATH>
        Path to Cargo.toml

    --no-default-features
        Do not activate the `default` feature

-p, --package <PACKAGE>
        Package to build (see `cargo help pkgid`)

    --profile <PROFILE>
        Specific profile to use (conflicts with `--release`)

-r, --release
        Compile for release mode (default is debug)

    --test
        Build in test mode (for `cargo pgx test`)

-v, --verbose
        Enable info logs, -vv for debug, -vvv for trace

-V, --version
        Print version information

```

Testing Your Extension

```shell script $ cargo pgx test "cargo" "test" "--features" " pg_test" Finished test [unoptimized + debuginfo] target(s) in 0.07s Running unittests (target/debug/deps/spi-312296af509607bc)

running 2 tests building extension with features pg_test "cargo" "build" "--features" " pg_test" "--message-format=json-render-diagnostics" Finished dev [unoptimized + debuginfo] target(s) in 0.06s

installing extension Copying control file to /home/ana/.pgx/13.5/pgx-install/share/postgresql/extension/spi.control Copying shared library to /home/ana/.pgx/13.5/pgx-install/lib/postgresql/spi.so Building for SQL generation with features pg_test Finished test [unoptimized + debuginfo] target(s) in 0.07s Discovering SQL entities Discovered 11 SQL entities: 1 schemas (1 unique), 8 functions, 0 types, 0 enums, 2 sqls, 0 ords, 0 hashes, 0 aggregates Writing SQL entities to /home/ana/.pgx/13.5/pgx-install/share/postgresql/extension/spi--0.0.0.sql Finished installing spi test tests::pgtestspiquerybyiddirect ... ok test tests::pgtestspiquerybyidvia_spi ... ok

test result: ok. 2 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 1.61s

Stopping Postgres ```

cargo pgx test [pg11 | pg12 | pg13 | pg14 | pg15] runs your #[test] and #[pg_test] annotated functions using cargo's test system.

During the testing process, pgx starts a tempory instance of Postgres with its PGDATA directory in ./target/pgx-test-data-PGVER/. This Postgres instance is stopped as soon as the test framework has finished.

The output is standard "cargo test" output along with some Postgres log output. In the case of test failures, the failure report will include any Postgres log messages generated by that particular test.

Rust #[test] functions behave normally, while #[pg_test] functions are run inside the Postgres instance and have full access to all of Postgres internals. All tests are run in parallel, regardless of their type.

Additionally, a #[pg_test] function runs in a transaction that is aborted when the test is finished. As such, any changes it might make to the database are not preserved.

```shell script cargo-pgx-test 0.5.0 ZomboDB, LLC zombodb@gmail.com Run the test suite for this crate

USAGE: cargo pgx test [OPTIONS] [ARGS]

ARGS: Do you want to run against Postgres pg11, pg12, pg13, pg14, pg15, or all? [env: PG_VERSION=] If specified, only run tests containing this string in their names

OPTIONS: --all-features Activate all available features

    --features <FEATURES>
        Space-separated list of features to activate

-h, --help
        Print help information

    --manifest-path <MANIFEST_PATH>
        Path to Cargo.toml

-n, --no-schema
        Don't regenerate the schema

    --no-default-features
        Do not activate the `default` feature

-p, --package <PACKAGE>
        Package to build (see `cargo help pkgid`)

    --profile <PROFILE>
        Specific profile to use (conflicts with `--release`)

-r, --release
        compile for release mode (default is debug)

-v, --verbose
        Enable info logs, -vv for debug, -vvv for trace

-V, --version
        Print version information

```

Building an Installation Package

`shell script $ cargo pgx package building extension with features "cargo" "build" "--release" "--message-format=json-render-diagnostics" Finished release [optimized] target(s) in 0.07s

installing extension Copying control file to target/release/spi-pg13/usr/share/postgresql/13/extension/spi.control Copying shared library to target/release/spi-pg13/usr/lib/postgresql/13/lib/spi.so Building for SQL generation with features `` Finished release [optimized] target(s) in 0.07s Discovering SQL entities Discovered 8 SQL entities: 0 schemas (0 unique), 6 functions, 0 types, 0 enums, 2 sqls, 0 ords, 0 hashes, 0 aggregates Writing SQL entities to target/release/spi-pg13/usr/share/postgresql/13/extension/spi--0.0.0.sql Finished installing spi ```

cargo pgx package [--debug] builds your extension, in --release mode, to a directory structure in ./target/[debug | release]/extension_name-PGVER using the Postgres installation path information from the pg_config tool on your $PATH.

The intent is that you'd then change into that directory and build a tarball or a .deb or .rpm package.

The directory structure cargo pgx package creates starts at the root of the filesystem, as a package-manager installed version of Postgres is likely to split pg_config --pkglibdir and pg_config --sharedir into different base paths.

(In the example screenshot above, cargo pgx package was used to build a directory structure using my manually installed version of Postgres 12.)

This command could be useful from Dockerfiles, for example, to automate building installation packages for various Linux distobutions or MacOS Postgres installations.

```shell script $ cargo pgx package --help cargo-pgx-package 0.5.0 ZomboDB, LLC zombodb@gmail.com Create an installation package directory

USAGE: cargo pgx package [OPTIONS]

OPTIONS: --all-features Activate all available features

-c, --pg-config <PG_CONFIG>
        The `pg_config` path (default is first in $PATH)

-d, --debug
        Compile for debug mode (default is release)

    --features <FEATURES>
        Space-separated list of features to activate

-h, --help
        Print help information

    --manifest-path <MANIFEST_PATH>
        Path to Cargo.toml

    --no-default-features
        Do not activate the `default` feature

    --out-dir <OUT_DIR>
        The directory to output the package (default is
        `./target/[debug|release]/extname-pgXX/`)

-p, --package <PACKAGE>
        Package to build (see `cargo help pkgid`)

    --profile <PROFILE>
        Specific profile to use (conflicts with `--debug`)

    --test
        Build in test mode (for `cargo pgx test`)

-v, --verbose
        Enable info logs, -vv for debug, -vvv for trace

-V, --version
        Print version information

```

Inspect your Extension Schema

If you just want to look at the full extension schema that pgx will generate, use cargo pgx schema.

```shell script $ cargo pgx schema --help cargo-pgx-schema 0.5.0 ZomboDB, LLC zombodb@gmail.com Generate extension schema files

USAGE: cargo pgx schema [OPTIONS] [PG_VERSION]

ARGS: Do you want to run against Postgres pg11, pg12, pg13, pg14, pg15?

OPTIONS: --all-features Activate all available features

-c, --pg-config <PG_CONFIG>
        The `pg_config` path (default is first in $PATH)

-d, --dot <DOT>
        A path to output a produced GraphViz DOT file

    --features <FEATURES>
        Space-separated list of features to activate

-h, --help
        Print help information

    --manifest-path <MANIFEST_PATH>
        Path to Cargo.toml

    --no-default-features
        Do not activate the `default` feature

-o, --out <OUT>
        A path to output a produced SQL file (default is `stdout`)

-p, --package <PACKAGE>
        Package to build (see `cargo help pkgid`)

    --profile <PROFILE>
        Specific profile to use (conflicts with `--release`)

-r, --release
        Compile for release mode (default is debug)

    --skip-build
        Skip building a fresh extension shared object

    --test
        Build in test mode (for `cargo pgx test`)

-v, --verbose
        Enable info logs, -vv for debug, -vvv for trace

-V, --version
        Print version information

```

EXPERIMENTAL: Versioned shared-object support

pgx experimentally supports the option to produce a versioned shared library. This allows multiple versions of the extension to be installed side-by-side, and can enable the deprecation (and removal) of functions between extension versions. There are some caveats which must be observed when using this functionality. For this reason it is currently experimental.

Activation

Versioned shared-object support is enabled by removing the module_pathname configuration value in the extension's .control file.

Concepts

Postgres has the implicit requirement that C extensions maintain ABI compatibility between versions. The idea behind this feature is to allow interoperability between two versions of an extension when the new version is not ABI compatible with the old version.

The mechanism of operation is to version the name of the shared library file, and to hard-code function definitions to point to the versioned shared library file. Without versioned shared-object support, the SQL definition of a C function would look as follows:

SQL CREATE OR REPLACE FUNCTION "hello_extension"() RETURNS text /* &str */ STRICT LANGUAGE c /* Rust */ AS 'MODULE_PATHNAME', 'hello_extension_wrapper';

MODULE_PATHNAME is replaced by Postgres with the configured value in the .control file. For pgx-based extensions, this is usually set to $libdir/<extension-name>.

When using versioned shared-object support, the same SQL would look as follows:

SQL CREATE OR REPLACE FUNCTION "hello_extension"() RETURNS text /* &str */ STRICT LANGUAGE c /* Rust */ AS '$libdir/extension-0.0.0', 'hello_extension_wrapper';

Note that the versioned shared library is hard-coded in the function definition. This corresponds to the extension-0.0.0.so file which pgx generates.

It is important to note that the emitted SQL is version-dependent. This means that all previously-defined C functions must be redefined to point to the current versioned-so in the version upgrade script. As an example, when updating the extension version to 0.1.0, the shared object will be named <extension-name>-0.1.0.so, and cargo pgx schema will produce the following SQL for the above function:

SQL CREATE OR REPLACE FUNCTION "hello_extension"() RETURNS text /* &str */ STRICT LANGUAGE c /* Rust */ AS '$libdir/extension-0.1.0', 'hello_extension_wrapper';

This SQL must be used in the upgrade script from 0.0.0 to 0.1.0 in order to point the hello_extension function to the new shared object. pgx does not do any magic to determine in which version a function was introduced or modified and only place it in the corresponding versioned so file. By extension, you can always expect that the shared library will contain all functions which are still defined in the extension's source code.

This feature is not designed to assist in the backwards compatibility of data types.

`@MODULE_PATHNAME@` Templating

In case you are already providing custom SQL definitions for Rust functions, you can use the @MODULE_PATHNAME@ template in your custom SQL. This value will be replaced with the path to the actual shared object.

The following example illustrates how this works:

```rust

[pg_extern(sql = r#"

CREATE OR REPLACE FUNCTION tests."overridden_sql_with_fn_name"() RETURNS void
STRICT
LANGUAGE c /* Rust */
AS '@MODULE_PATHNAME@', '@FUNCTION_NAME@';

"#)] fn overriddensqlwithfnname() -> bool { true } ```

Caveats

There are some scenarios which are entirely incompatible with this feature, because they rely on some global state in Postgres, so loading two versions of the shared library will cause trouble.

These scenarios are: - when using shared memory - when using query planner hooks

cargo-pgx

Installing

Usage

Environment Variables

First Time Initialization

Creating a new Extension

Managing Your Postgres Installations

Compiling and Running Your Extension

to_lowercase

Connect to a Database

to_lowercase

Installing Your Extension Locally

Testing Your Extension

Building an Installation Package

Inspect your Extension Schema

EXPERIMENTAL: Versioned shared-object support

Activation

Concepts

@MODULE_PATHNAME@ Templating

[pg_extern(sql = r#"

Caveats

`@MODULE_PATHNAME@` Templating