feat(citext): support postgres citext (launchbadge#2478)

* feat(citext): implement citext for postgres

* feat(citext): add citext -> String conversion test

* feat(citext): fix ltree -> citree

* feat(citext): add citext to the setup.sql

* chore: address nits to launchbadge#2478

* Rename `PgCitext` to `PgCiText`
* Document when use of `PgCiText` is warranted
* Document potentially surprising `PartialEq` behavior
* Test that the macros consider `CITEXT` to be compatible with `String` and friends

* doc: add `PgCiText` to `postgres::types` listing

* chore: restore missing trailing line break to `tests/postgres/setup.sql`

---------

Co-authored-by: Austin Bonander <austin@launchbadge.com>

sqlx-postgres/src/any.rs

@@ -13,6 +13,7 @@ use sqlx_core::connection::Connection;
 use sqlx_core::database::Database;
 use sqlx_core::describe::Describe;
 use sqlx_core::executor::Executor;
+use sqlx_core::ext::ustr::UStr;
 use sqlx_core::transaction::TransactionManager;
 
 sqlx_core::declare_driver_with_optional_migrate!(DRIVER = Postgres);
@@ -178,6 +179,7 @@ impl<'a> TryFrom<&'a PgTypeInfo> for AnyTypeInfo {
                 PgType::Float8 => AnyTypeInfoKind::Double,
                 PgType::Bytea => AnyTypeInfoKind::Blob,
                 PgType::Text => AnyTypeInfoKind::Text,
+                PgType::DeclareWithName(UStr::Static("citext")) => AnyTypeInfoKind::Text,
                 _ => {
                     return Err(sqlx_core::Error::AnyDriverError(
                         format!("Any driver does not support the Postgres type {pg_type:?}").into(),

sqlx-postgres/src/type_info.rs

@@ -457,6 +457,7 @@ impl PgType {
             PgType::Int8RangeArray => Oid(3927),
             PgType::Jsonpath => Oid(4072),
             PgType::JsonpathArray => Oid(4073),
+
             PgType::Custom(ty) => ty.oid,
 
             PgType::DeclareWithOid(oid) => *oid,
@@ -874,6 +875,7 @@ impl PgType {
             PgType::Unknown => None,
             // There is no `VoidArray`
             PgType::Void => None,
+
             PgType::Custom(ty) => match &ty.kind {
                 PgTypeKind::Simple => None,
                 PgTypeKind::Pseudo => None,

sqlx-postgres/src/types/citext.rs

@@ -0,0 +1,106 @@
+use crate::types::array_compatible;
+use crate::{PgArgumentBuffer, PgHasArrayType, PgTypeInfo, PgValueRef, Postgres};
+use sqlx_core::decode::Decode;
+use sqlx_core::encode::{Encode, IsNull};
+use sqlx_core::error::BoxDynError;
+use sqlx_core::types::Type;
+use std::fmt;
+use std::fmt::{Debug, Display, Formatter};
+use std::ops::Deref;
+use std::str::FromStr;
+
+/// Case-insensitive text (`citext`) support for Postgres.
+///
+/// Note that SQLx considers the `citext` type to be compatible with `String`
+/// and its various derivatives, so direct usage of this type is generally unnecessary.
+///
+/// However, it may be needed, for example, when binding a `citext[]` array,
+/// as Postgres will generally not accept a `text[]` array (mapped from `Vec<String>`) in its place.
+///
+/// See [the Postgres manual, Appendix F, Section 10][PG.F.10] for details on using `citext`.
+///
+/// [PG.F.10]: https://www.postgresql.org/docs/current/citext.html
+///
+/// ### Note: Extension Required
+/// The `citext` extension is not enabled by default in Postgres. You will need to do so explicitly:
+///
+/// ```ignore
+/// CREATE EXTENSION IF NOT EXISTS "citext";
+/// ```
+///
+/// ### Note: `PartialEq` is Case-Sensitive
+/// This type derives `PartialEq` which forwards to the implementation on `String`, which
+/// is case-sensitive. This impl exists mainly for testing.
+///
+/// To properly emulate the case-insensitivity of `citext` would require use of locale-aware
+/// functions in `libc`, and even then would require querying the locale of the database server
+/// and setting it locally, which is unsafe.
+#[derive(Clone, Debug, Default, PartialEq)]
+pub struct PgCiText(pub String);
+
+impl Type<Postgres> for PgCiText {
+    fn type_info() -> PgTypeInfo {
+        // Since `citext` is enabled by an extension, it does not have a stable OID.
+        PgTypeInfo::with_name("citext")
+    }
+
+    fn compatible(ty: &PgTypeInfo) -> bool {
+        <&str as Type<Postgres>>::compatible(ty)
+    }
+}
+
+impl Deref for PgCiText {
+    type Target = str;
+
+    fn deref(&self) -> &Self::Target {
+        self.0.as_str()
+    }
+}
+
+impl From<String> for PgCiText {
+    fn from(value: String) -> Self {
+        Self(value)
+    }
+}
+
+impl From<PgCiText> for String {
+    fn from(value: PgCiText) -> Self {
+        value.0
+    }
+}
+
+impl FromStr for PgCiText {
+    type Err = core::convert::Infallible;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        Ok(PgCiText(s.parse()?))
+    }
+}
+
+impl Display for PgCiText {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
+        f.write_str(&self.0)
+    }
+}
+
+impl PgHasArrayType for PgCiText {
+    fn array_type_info() -> PgTypeInfo {
+        PgTypeInfo::with_name("_citext")
+    }
+
+    fn array_compatible(ty: &PgTypeInfo) -> bool {
+        array_compatible::<&str>(ty)
+    }
+}
+
+impl Encode<'_, Postgres> for PgCiText {
+    fn encode_by_ref(&self, buf: &mut PgArgumentBuffer) -> IsNull {
+        <&str as Encode<Postgres>>::encode(&**self, buf)
+    }
+}
+
+impl Decode<'_, Postgres> for PgCiText {
+    fn decode(value: PgValueRef<'_>) -> Result<Self, BoxDynError> {
+        Ok(PgCiText(value.as_str()?.to_owned()))
+    }
+}

sqlx-postgres/src/types/mod.rs

@@ -11,14 +11,19 @@
 //! | `i64`                                 | BIGINT, BIGSERIAL, INT8                              |
 //! | `f32`                                 | REAL, FLOAT4                                         |
 //! | `f64`                                 | DOUBLE PRECISION, FLOAT8                             |
-//! | `&str`, [`String`]                    | VARCHAR, CHAR(N), TEXT, NAME                         |
+//! | `&str`, [`String`]                    | VARCHAR, CHAR(N), TEXT, NAME, CITEXT                 |
 //! | `&[u8]`, `Vec<u8>`                    | BYTEA                                                |
 //! | `()`                                  | VOID                                                 |
 //! | [`PgInterval`]                        | INTERVAL                                             |
 //! | [`PgRange<T>`](PgRange)               | INT8RANGE, INT4RANGE, TSRANGE, TSTZRANGE, DATERANGE, NUMRANGE |
 //! | [`PgMoney`]                           | MONEY                                                |
 //! | [`PgLTree`]                           | LTREE                                                |
 //! | [`PgLQuery`]                          | LQUERY                                               |
+//! | [`PgCiText`]                          | CITEXT<sup>1</sup>                                   |
+//!
+//! <sup>1</sup> SQLx generally considers `CITEXT` to be compatible with `String`, `&str`, etc.,
+//! but this wrapper type is available for edge cases, such as `CITEXT[]` which Postgres
+//! does not consider to be compatible with `TEXT[]`.
 //!
 //! ### [`bigdecimal`](https://crates.io/crates/bigdecimal)
 //! Requires the `bigdecimal` Cargo feature flag.
@@ -175,6 +180,7 @@ pub(crate) use sqlx_core::types::{Json, Type};
 mod array;
 mod bool;
 mod bytes;
+mod citext;
 mod float;
 mod int;
 mod interval;
@@ -224,6 +230,7 @@ mod mac_address;
 mod bit_vec;
 
 pub use array::PgHasArrayType;
+pub use citext::PgCiText;
 pub use interval::PgInterval;
 pub use lquery::PgLQuery;
 pub use lquery::PgLQueryLevel;

sqlx-postgres/src/types/str.rs

@@ -18,6 +18,7 @@ impl Type<Postgres> for str {
             PgTypeInfo::BPCHAR,
             PgTypeInfo::VARCHAR,
             PgTypeInfo::UNKNOWN,
+            PgTypeInfo::with_name("citext"),
         ]
         .contains(ty)
     }

tests/postgres/macros.rs

@@ -611,3 +611,28 @@ async fn test_bind_arg_override_wildcard() -> anyhow::Result<()> {
 
     Ok(())
 }
+
+#[sqlx_macros::test]
+async fn test_to_from_citext() -> anyhow::Result<()> {
+    // Ensure that the macros consider `CITEXT` to be compatible with `String` and friends
+
+    let mut conn = new::<Postgres>().await?;
+
+    let mut tx = conn.begin().await?;
+
+    let foo_in = "Hello, world!";
+
+    sqlx::query!("insert into test_citext(foo) values ($1)", foo_in)
+        .execute(&mut *tx)
+        .await?;
+
+    let foo_out: String = sqlx::query_scalar!("select foo from test_citext")
+        .fetch_one(&mut *tx)
+        .await?;
+
+    assert_eq!(foo_in, foo_out);
+
+    tx.rollback().await?;
+
+    Ok(())
+}

tests/postgres/setup.sql

@@ -1,6 +1,9 @@
 -- https://www.postgresql.org/docs/current/ltree.html
 CREATE EXTENSION IF NOT EXISTS ltree;
 
+-- https://www.postgresql.org/docs/current/citext.html
+CREATE EXTENSION IF NOT EXISTS citext;
+
 -- https://www.postgresql.org/docs/current/sql-createtype.html
 CREATE TYPE status AS ENUM ('new', 'open', 'closed');
 
@@ -44,3 +47,7 @@ CREATE TABLE products (
 
 CREATE OR REPLACE PROCEDURE forty_two(INOUT forty_two INT = NULL)
     LANGUAGE plpgsql AS 'begin forty_two := 42; end;';
+
+CREATE TABLE test_citext (
+    foo CITEXT NOT NULL
+);

tests/postgres/types.rs

@@ -2,7 +2,7 @@ extern crate time_ as time;
 
 use std::ops::Bound;
 
-use sqlx::postgres::types::{Oid, PgInterval, PgMoney, PgRange};
+use sqlx::postgres::types::{Oid, PgCiText, PgInterval, PgMoney, PgRange};
 use sqlx::postgres::Postgres;
 use sqlx_test::{test_decode_type, test_prepared_type, test_type};
 
@@ -65,6 +65,7 @@ test_type!(str<&str>(Postgres,
     "'identifier'::name" == "identifier",
     "'five'::char(4)" == "five",
     "'more text'::varchar" == "more text",
+    "'case insensitive searching'::citext" == "case insensitive searching",
 ));
 
 test_type!(string<String>(Postgres,
@@ -79,7 +80,7 @@ test_type!(string_vec<Vec<String>>(Postgres,
         == vec!["", "\""],
 
     "array['Hello, World', '', 'Goodbye']::text[]"
-        == vec!["Hello, World", "", "Goodbye"]
+        == vec!["Hello, World", "", "Goodbye"],
 ));
 
 test_type!(string_array<[String; 3]>(Postgres,
@@ -550,6 +551,14 @@ test_prepared_type!(money_vec<Vec<PgMoney>>(Postgres,
     "array[123.45,420.00,666.66]::money[]" == vec![PgMoney(12345), PgMoney(42000), PgMoney(66666)],
 ));
 
+test_prepared_type!(citext_array<Vec<PgCiText>>(Postgres,
+    "array['one','two','three']::citext[]" == vec![
+        PgCiText("one".to_string()),
+        PgCiText("two".to_string()),
+        PgCiText("three".to_string()),
+    ],
+));
+
 // FIXME: needed to disable `ltree` tests in version that don't have a binary format for it
 // but `PgLTree` should just fall back to text format
 #[cfg(any(postgres_14, postgres_15))]