PostgreSQL: Support PRIMARY KEY/UNIQUE USING INDEX

src/ast/mod.rs

@@ -134,8 +134,8 @@ mod dml;
 pub mod helpers;
 pub mod table_constraints;
 pub use table_constraints::{
-    CheckConstraint, ForeignKeyConstraint, FullTextOrSpatialConstraint, IndexConstraint,
-    PrimaryKeyConstraint, TableConstraint, UniqueConstraint,
+    CheckConstraint, ConstraintUsingIndex, ForeignKeyConstraint, FullTextOrSpatialConstraint,
+    IndexConstraint, PrimaryKeyConstraint, TableConstraint, UniqueConstraint,
 };
 mod operator;
 mod query;

src/ast/spans.rs

@@ -624,6 +624,7 @@ impl Spanned for TableConstraint {
             TableConstraint::Check(constraint) => constraint.span(),
             TableConstraint::Index(constraint) => constraint.span(),
             TableConstraint::FulltextOrSpatial(constraint) => constraint.span(),
+            TableConstraint::ConstraintUsingIndex(constraint) => constraint.span(),
         }
     }
 }

src/ast/table_constraints.rs

@@ -101,6 +101,14 @@ pub enum TableConstraint {
     /// [1]: https://dev.mysql.com/doc/refman/8.0/en/fulltext-natural-language.html
     /// [2]: https://dev.mysql.com/doc/refman/8.0/en/spatial-types.html
     FulltextOrSpatial(FullTextOrSpatialConstraint),
+    /// PostgreSQL [definition][1] for promoting an existing unique index to a
+    /// `PRIMARY KEY` or `UNIQUE` constraint:
+    ///
+    /// `[ CONSTRAINT constraint_name ] { UNIQUE | PRIMARY KEY } USING INDEX index_name
+    ///   [ DEFERRABLE | NOT DEFERRABLE ] [ INITIALLY DEFERRED | INITIALLY IMMEDIATE ]`
+    ///
+    /// [1]: https://www.postgresql.org/docs/current/sql-altertable.html
+    ConstraintUsingIndex(ConstraintUsingIndex),
 }
 
 impl From<UniqueConstraint> for TableConstraint {
@@ -139,6 +147,12 @@ impl From<FullTextOrSpatialConstraint> for TableConstraint {
     }
 }
 
+impl From<ConstraintUsingIndex> for TableConstraint {
+    fn from(constraint: ConstraintUsingIndex) -> Self {
+        TableConstraint::ConstraintUsingIndex(constraint)
+    }
+}
+
 impl fmt::Display for TableConstraint {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         match self {
@@ -148,6 +162,7 @@ impl fmt::Display for TableConstraint {
             TableConstraint::Check(constraint) => constraint.fmt(f),
             TableConstraint::Index(constraint) => constraint.fmt(f),
             TableConstraint::FulltextOrSpatial(constraint) => constraint.fmt(f),
+            TableConstraint::ConstraintUsingIndex(constraint) => constraint.fmt(f),
         }
     }
 }
@@ -535,3 +550,58 @@ impl crate::ast::Spanned for UniqueConstraint {
         )
     }
 }
+
+/// PostgreSQL constraint that promotes an existing unique index to a table constraint.
+///
+/// `[ CONSTRAINT constraint_name ] { UNIQUE | PRIMARY KEY } USING INDEX index_name
+///   [ DEFERRABLE | NOT DEFERRABLE ] [ INITIALLY DEFERRED | INITIALLY IMMEDIATE ]`
+///
+/// See <https://www.postgresql.org/docs/current/sql-altertable.html>
+#[derive(Debug, Clone, PartialEq, PartialOrd, Eq, Ord, Hash)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "visitor", derive(Visit, VisitMut))]
+pub struct ConstraintUsingIndex {
+    /// Optional constraint name.
+    pub name: Option<Ident>,
+    /// Whether this is a `PRIMARY KEY` (true) or `UNIQUE` (false) constraint.
+    pub is_primary_key: bool,
+    /// The name of the existing unique index to promote.
+    pub index_name: Ident,
+    /// Optional characteristics like `DEFERRABLE`.
+    pub characteristics: Option<ConstraintCharacteristics>,
+}
+
+impl fmt::Display for ConstraintUsingIndex {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        use crate::ast::ddl::{display_constraint_name, display_option_spaced};
+        write!(
+            f,
+            "{}{} USING INDEX {}",
+            display_constraint_name(&self.name),
+            if self.is_primary_key {
+                "PRIMARY KEY"
+            } else {
+                "UNIQUE"
+            },
+            self.index_name,
+        )?;
+        write!(f, "{}", display_option_spaced(&self.characteristics))?;
+        Ok(())
+    }
+}
+
+impl crate::ast::Spanned for ConstraintUsingIndex {
+    fn span(&self) -> Span {
+        let start = self
+            .name
+            .as_ref()
+            .map(|i| i.span)
+            .unwrap_or(self.index_name.span);
+        let end = self
+            .characteristics
+            .as_ref()
+            .map(|c| c.span())
+            .unwrap_or(self.index_name.span);
+        start.union(&end)
+    }
+}

src/parser/mod.rs

@@ -9314,6 +9314,22 @@ impl<'a> Parser<'a> {
         let next_token = self.next_token();
         match next_token.token {
             Token::Word(w) if w.keyword == Keyword::UNIQUE => {
+                // PostgreSQL: UNIQUE USING INDEX index_name
+                // https://www.postgresql.org/docs/current/sql-altertable.html
+                if self.parse_keywords(&[Keyword::USING, Keyword::INDEX]) {
+                    let index_name = self.parse_identifier()?;
+                    let characteristics = self.parse_constraint_characteristics()?;
+                    return Ok(Some(
+                        ConstraintUsingIndex {
+                            name,
+                            is_primary_key: false,
+                            index_name,
+                            characteristics,
+                        }
+                        .into(),
+                    ));
+                }
+
                 let index_type_display = self.parse_index_type_display();
                 if !dialect_of!(self is GenericDialect | MySqlDialect)
                     && !index_type_display.is_none()
@@ -9349,6 +9365,22 @@ impl<'a> Parser<'a> {
                 // after `PRIMARY` always stay `KEY`
                 self.expect_keyword_is(Keyword::KEY)?;
 
+                // PostgreSQL: PRIMARY KEY USING INDEX index_name
+                // https://www.postgresql.org/docs/current/sql-altertable.html
+                if self.parse_keywords(&[Keyword::USING, Keyword::INDEX]) {
+                    let index_name = self.parse_identifier()?;
+                    let characteristics = self.parse_constraint_characteristics()?;
+                    return Ok(Some(
+                        ConstraintUsingIndex {
+                            name,
+                            is_primary_key: true,
+                            index_name,
+                            characteristics,
+                        }
+                        .into(),
+                    ));
+                }
+
                 // optional index name
                 let index_name = self.parse_optional_ident()?;
                 let index_type = self.parse_optional_using_then_index_type()?;

tests/sqlparser_postgres.rs

@@ -627,6 +627,46 @@ fn parse_alter_table_constraints_unique_nulls_distinct() {
     pg_and_generic().verified_stmt("ALTER TABLE t ADD CONSTRAINT b UNIQUE (c)");
 }
 
+#[test]
+fn parse_alter_table_constraint_using_index() {
+    // PRIMARY KEY USING INDEX
+    // https://www.postgresql.org/docs/current/sql-altertable.html
+    let sql = "ALTER TABLE tab ADD CONSTRAINT c PRIMARY KEY USING INDEX my_index";
+    match pg_and_generic().verified_stmt(sql) {
+        Statement::AlterTable(alter_table) => match &alter_table.operations[0] {
+            AlterTableOperation::AddConstraint {
+                constraint: TableConstraint::ConstraintUsingIndex(c),
+                ..
+            } => {
+                assert_eq!(c.name.as_ref().unwrap().to_string(), "c");
+                assert!(c.is_primary_key);
+                assert_eq!(c.index_name.to_string(), "my_index");
+                assert!(c.characteristics.is_none());
+            }
+            _ => unreachable!(),
+        },
+        _ => unreachable!(),
+    }
+
+    // UNIQUE USING INDEX
+    pg_and_generic().verified_stmt("ALTER TABLE tab ADD CONSTRAINT c UNIQUE USING INDEX my_index");
+
+    // Without constraint name
+    pg_and_generic().verified_stmt("ALTER TABLE tab ADD PRIMARY KEY USING INDEX my_index");
+    pg_and_generic().verified_stmt("ALTER TABLE tab ADD UNIQUE USING INDEX my_index");
+
+    // With DEFERRABLE
+    pg_and_generic().verified_stmt(
+        "ALTER TABLE tab ADD CONSTRAINT c PRIMARY KEY USING INDEX my_index DEFERRABLE",
+    );
+    pg_and_generic().verified_stmt(
+        "ALTER TABLE tab ADD CONSTRAINT c UNIQUE USING INDEX my_index NOT DEFERRABLE INITIALLY IMMEDIATE",
+    );
+    pg_and_generic().verified_stmt(
+        "ALTER TABLE tab ADD CONSTRAINT c PRIMARY KEY USING INDEX my_index DEFERRABLE INITIALLY DEFERRED",
+    );
+}
+
 #[test]
 fn parse_alter_table_disable() {
     pg_and_generic().verified_stmt("ALTER TABLE tab DISABLE ROW LEVEL SECURITY");