Adding support for parsing CREATE TRIGGER and DROP TRIGGER statements (#1352)

Co-authored-by: hulk <hulk.website@gmail.com>
Co-authored-by: Ifeanyi Ubah <ify1992@yahoo.com>
Co-authored-by: Andrew Lamb <andrew@nerdnetworks.org>

src/ast/data_type.rs

@@ -319,6 +319,10 @@ pub enum DataType {
     /// [`SQLiteDialect`](crate::dialect::SQLiteDialect), from statements such
     /// as `CREATE TABLE t1 (a)`.
     Unspecified,
+    /// Trigger data type, returned by functions associated with triggers
+    ///
+    /// [postgresql]: https://www.postgresql.org/docs/current/plpgsql-trigger.html
+    Trigger,
 }
 
 impl fmt::Display for DataType {
@@ -543,6 +547,7 @@ impl fmt::Display for DataType {
                 write!(f, "Nested({})", display_comma_separated(fields))
             }
             DataType::Unspecified => Ok(()),
+            DataType::Trigger => write!(f, "TRIGGER"),
         }
     }
 }

src/ast/ddl.rs

@@ -1175,7 +1175,7 @@ fn display_option_spaced<T: fmt::Display>(option: &Option<T>) -> impl fmt::Displ
 /// `<constraint_characteristics> = [ DEFERRABLE | NOT DEFERRABLE ] [ INITIALLY DEFERRED | INITIALLY IMMEDIATE ] [ ENFORCED | NOT ENFORCED ]`
 ///
 /// Used in UNIQUE and foreign key constraints. The individual settings may occur in any order.
-#[derive(Debug, Copy, Clone, PartialEq, PartialOrd, Eq, Ord, Hash)]
+#[derive(Debug, Copy, Clone, PartialEq, PartialOrd, Default, Eq, Ord, Hash)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 #[cfg_attr(feature = "visitor", derive(Visit, VisitMut))]
 pub struct ConstraintCharacteristics {

src/ast/mod.rs

@@ -53,6 +53,12 @@ pub use self::query::{
     TableAlias, TableFactor, TableFunctionArgs, TableVersion, TableWithJoins, Top, TopQuantity,
     ValueTableMode, Values, WildcardAdditionalOptions, With, WithFill,
 };
+
+pub use self::trigger::{
+    TriggerEvent, TriggerExecBody, TriggerExecBodyType, TriggerObject, TriggerPeriod,
+    TriggerReferencing, TriggerReferencingType,
+};
+
 pub use self::value::{
     escape_double_quote_string, escape_quoted_string, DateTimeField, DollarQuotedString,
     TrimWhereField, Value,
@@ -71,6 +77,7 @@ mod dml;
 pub mod helpers;
 mod operator;
 mod query;
+mod trigger;
 mod value;
 
 #[cfg(feature = "visitor")]
@@ -2282,7 +2289,7 @@ pub enum Statement {
     DropFunction {
         if_exists: bool,
         /// One or more function to drop
-        func_desc: Vec<DropFunctionDesc>,
+        func_desc: Vec<FunctionDesc>,
         /// `CASCADE` or `RESTRICT`
         option: Option<ReferentialAction>,
     },
@@ -2292,7 +2299,7 @@ pub enum Statement {
     DropProcedure {
         if_exists: bool,
         /// One or more function to drop
-        proc_desc: Vec<DropFunctionDesc>,
+        proc_desc: Vec<FunctionDesc>,
         /// `CASCADE` or `RESTRICT`
         option: Option<ReferentialAction>,
     },
@@ -2618,6 +2625,96 @@ pub enum Statement {
         /// [BigQuery](https://cloud.google.com/bigquery/docs/reference/standard-sql/data-definition-language#create_a_remote_function)
         remote_connection: Option<ObjectName>,
     },
+    /// CREATE TRIGGER
+    ///
+    /// Examples:
+    ///
+    /// ```sql
+    /// CREATE TRIGGER trigger_name
+    /// BEFORE INSERT ON table_name
+    /// FOR EACH ROW
+    /// EXECUTE FUNCTION trigger_function();
+    /// ```
+    ///
+    /// Postgres: <https://www.postgresql.org/docs/current/sql-createtrigger.html>
+    CreateTrigger {
+        /// The `OR REPLACE` clause is used to re-create the trigger if it already exists.
+        ///
+        /// Example:
+        /// ```sql
+        /// CREATE OR REPLACE TRIGGER trigger_name
+        /// AFTER INSERT ON table_name
+        /// FOR EACH ROW
+        /// EXECUTE FUNCTION trigger_function();
+        /// ```
+        or_replace: bool,
+        /// The `CONSTRAINT` keyword is used to create a trigger as a constraint.
+        is_constraint: bool,
+        /// The name of the trigger to be created.
+        name: ObjectName,
+        /// Determines whether the function is called before, after, or instead of the event.
+        ///
+        /// Example of BEFORE:
+        ///
+        /// ```sql
+        /// CREATE TRIGGER trigger_name
+        /// BEFORE INSERT ON table_name
+        /// FOR EACH ROW
+        /// EXECUTE FUNCTION trigger_function();
+        /// ```
+        ///
+        /// Example of AFTER:
+        ///
+        /// ```sql
+        /// CREATE TRIGGER trigger_name
+        /// AFTER INSERT ON table_name
+        /// FOR EACH ROW
+        /// EXECUTE FUNCTION trigger_function();
+        /// ```
+        ///
+        /// Example of INSTEAD OF:
+        ///
+        /// ```sql
+        /// CREATE TRIGGER trigger_name
+        /// INSTEAD OF INSERT ON table_name
+        /// FOR EACH ROW
+        /// EXECUTE FUNCTION trigger_function();
+        /// ```
+        period: TriggerPeriod,
+        /// Multiple events can be specified using OR, such as `INSERT`, `UPDATE`, `DELETE`, or `TRUNCATE`.
+        events: Vec<TriggerEvent>,
+        /// The table on which the trigger is to be created.
+        table_name: ObjectName,
+        /// The optional referenced table name that can be referenced via
+        /// the `FROM` keyword.
+        referenced_table_name: Option<ObjectName>,
+        /// This keyword immediately precedes the declaration of one or two relation names that provide access to the transition relations of the triggering statement.
+        referencing: Vec<TriggerReferencing>,
+        /// This specifies whether the trigger function should be fired once for
+        /// every row affected by the trigger event, or just once per SQL statement.
+        trigger_object: TriggerObject,
+        /// Whether to include the `EACH` term of the `FOR EACH`, as it is optional syntax.
+        include_each: bool,
+        ///  Triggering conditions
+        condition: Option<Expr>,
+        /// Execute logic block
+        exec_body: TriggerExecBody,
+        /// The characteristic of the trigger, which include whether the trigger is `DEFERRABLE`, `INITIALLY DEFERRED`, or `INITIALLY IMMEDIATE`,
+        characteristics: Option<ConstraintCharacteristics>,
+    },
+    /// DROP TRIGGER
+    ///
+    /// ```sql
+    /// DROP TRIGGER [ IF EXISTS ] name ON table_name [ CASCADE | RESTRICT ]
+    /// ```
+    ///
+    DropTrigger {
+        if_exists: bool,
+        trigger_name: ObjectName,
+        table_name: ObjectName,
+        /// `CASCADE` or `RESTRICT`
+        option: Option<ReferentialAction>,
+    },
     /// ```sql
     /// CREATE PROCEDURE
     /// ```
@@ -3394,6 +3491,71 @@ impl fmt::Display for Statement {
                 }
                 Ok(())
             }
+            Statement::CreateTrigger {
+                or_replace,
+                is_constraint,
+                name,
+                period,
+                events,
+                table_name,
+                referenced_table_name,
+                referencing,
+                trigger_object,
+                condition,
+                include_each,
+                exec_body,
+                characteristics,
+            } => {
+                write!(
+                    f,
+                    "CREATE {or_replace}{is_constraint}TRIGGER {name} {period}",
+                    or_replace = if *or_replace { "OR REPLACE " } else { "" },
+                    is_constraint = if *is_constraint { "CONSTRAINT " } else { "" },
+                )?;
+
+                if !events.is_empty() {
+                    write!(f, " {}", display_separated(events, " OR "))?;
+                }
+                write!(f, " ON {table_name}")?;
+
+                if let Some(referenced_table_name) = referenced_table_name {
+                    write!(f, " FROM {referenced_table_name}")?;
+                }
+
+                if let Some(characteristics) = characteristics {
+                    write!(f, " {characteristics}")?;
+                }
+
+                if !referencing.is_empty() {
+                    write!(f, " REFERENCING {}", display_separated(referencing, " "))?;
+                }
+
+                if *include_each {
+                    write!(f, " FOR EACH {trigger_object}")?;
+                } else {
+                    write!(f, " FOR {trigger_object}")?;
+                }
+                if let Some(condition) = condition {
+                    write!(f, " WHEN {condition}")?;
+                }
+                write!(f, " EXECUTE {exec_body}")
+            }
+            Statement::DropTrigger {
+                if_exists,
+                trigger_name,
+                table_name,
+                option,
+            } => {
+                write!(f, "DROP TRIGGER")?;
+                if *if_exists {
+                    write!(f, " IF EXISTS")?;
+                }
+                write!(f, " {trigger_name} ON {table_name}")?;
+                if let Some(option) = option {
+                    write!(f, " {option}")?;
+                }
+                Ok(())
+            }
             Statement::CreateProcedure {
                 name,
                 or_alter,
@@ -6026,16 +6188,16 @@ impl fmt::Display for DropFunctionOption {
     }
 }
 
-/// Function describe in DROP FUNCTION.
+/// Generic function description for DROP FUNCTION and CREATE TRIGGER.
 #[derive(Debug, Clone, PartialEq, PartialOrd, Eq, Ord, Hash)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 #[cfg_attr(feature = "visitor", derive(Visit, VisitMut))]
-pub struct DropFunctionDesc {
+pub struct FunctionDesc {
     pub name: ObjectName,
     pub args: Option<Vec<OperateFunctionArg>>,
 }
 
-impl fmt::Display for DropFunctionDesc {
+impl fmt::Display for FunctionDesc {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         write!(f, "{}", self.name)?;
         if let Some(args) = &self.args {

src/ast/trigger.rs

@@ -0,0 +1,158 @@
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//! SQL Abstract Syntax Tree (AST) for triggers.
+use super::*;
+
+/// This specifies whether the trigger function should be fired once for every row affected by the trigger event, or just once per SQL statement.
+#[derive(Debug, Clone, Copy, PartialEq, PartialOrd, Eq, Ord, Hash)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "visitor", derive(Visit, VisitMut))]
+pub enum TriggerObject {
+    Row,
+    Statement,
+}
+
+impl fmt::Display for TriggerObject {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            TriggerObject::Row => write!(f, "ROW"),
+            TriggerObject::Statement => write!(f, "STATEMENT"),
+        }
+    }
+}
+
+/// This clause indicates whether the following relation name is for the before-image transition relation or the after-image transition relation
+#[derive(Debug, Clone, Copy, PartialEq, PartialOrd, Eq, Ord, Hash)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "visitor", derive(Visit, VisitMut))]
+pub enum TriggerReferencingType {
+    OldTable,
+    NewTable,
+}
+
+impl fmt::Display for TriggerReferencingType {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            TriggerReferencingType::OldTable => write!(f, "OLD TABLE"),
+            TriggerReferencingType::NewTable => write!(f, "NEW TABLE"),
+        }
+    }
+}
+
+/// This keyword immediately precedes the declaration of one or two relation names that provide access to the transition relations of the triggering statement
+#[derive(Debug, Clone, PartialEq, PartialOrd, Eq, Ord, Hash)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "visitor", derive(Visit, VisitMut))]
+pub struct TriggerReferencing {
+    pub refer_type: TriggerReferencingType,
+    pub is_as: bool,
+    pub transition_relation_name: ObjectName,
+}
+
+impl fmt::Display for TriggerReferencing {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(
+            f,
+            "{refer_type}{is_as} {relation_name}",
+            refer_type = self.refer_type,
+            is_as = if self.is_as { " AS" } else { "" },
+            relation_name = self.transition_relation_name
+        )
+    }
+}
+
+/// Used to describe trigger events
+#[derive(Debug, Clone, PartialEq, PartialOrd, Eq, Ord, Hash)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "visitor", derive(Visit, VisitMut))]
+pub enum TriggerEvent {
+    Insert,
+    Update(Vec<Ident>),
+    Delete,
+    Truncate,
+}
+
+impl fmt::Display for TriggerEvent {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            TriggerEvent::Insert => write!(f, "INSERT"),
+            TriggerEvent::Update(columns) => {
+                write!(f, "UPDATE")?;
+                if !columns.is_empty() {
+                    write!(f, " OF")?;
+                    write!(f, " {}", display_comma_separated(columns))?;
+                }
+                Ok(())
+            }
+            TriggerEvent::Delete => write!(f, "DELETE"),
+            TriggerEvent::Truncate => write!(f, "TRUNCATE"),
+        }
+    }
+}
+
+/// Trigger period
+#[derive(Debug, Clone, Copy, PartialEq, PartialOrd, Eq, Ord, Hash)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "visitor", derive(Visit, VisitMut))]
+pub enum TriggerPeriod {
+    After,
+    Before,
+    InsteadOf,
+}
+
+impl fmt::Display for TriggerPeriod {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            TriggerPeriod::After => write!(f, "AFTER"),
+            TriggerPeriod::Before => write!(f, "BEFORE"),
+            TriggerPeriod::InsteadOf => write!(f, "INSTEAD OF"),
+        }
+    }
+}
+
+/// Types of trigger body execution body.
+#[derive(Debug, Clone, Copy, PartialEq, PartialOrd, Eq, Ord, Hash)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "visitor", derive(Visit, VisitMut))]
+pub enum TriggerExecBodyType {
+    Function,
+    Procedure,
+}
+
+impl fmt::Display for TriggerExecBodyType {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            TriggerExecBodyType::Function => write!(f, "FUNCTION"),
+            TriggerExecBodyType::Procedure => write!(f, "PROCEDURE"),
+        }
+    }
+}
+/// This keyword immediately precedes the declaration of one or two relation names that provide access to the transition relations of the triggering statement
+#[derive(Debug, Clone, PartialEq, PartialOrd, Eq, Ord, Hash)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "visitor", derive(Visit, VisitMut))]
+pub struct TriggerExecBody {
+    pub exec_type: TriggerExecBodyType,
+    pub func_desc: FunctionDesc,
+}
+
+impl fmt::Display for TriggerExecBody {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(
+            f,
+            "{exec_type} {func_desc}",
+            exec_type = self.exec_type,
+            func_desc = self.func_desc
+        )
+    }
+}

src/keywords.rs

@@ -20,7 +20,7 @@
 //!     As a matter of fact, most of these keywords are not used at all
 //!     and could be removed.
 //! 3) a `RESERVED_FOR_TABLE_ALIAS` array with keywords reserved in a
-//!    "table alias" context.
+//!     "table alias" context.
 
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
@@ -108,6 +108,7 @@ define_keywords!(
     AVRO,
     BACKWARD,
     BASE64,
+    BEFORE,
     BEGIN,
     BEGIN_FRAME,
     BEGIN_PARTITION,
@@ -378,6 +379,7 @@ define_keywords!(
     INSENSITIVE,
     INSERT,
     INSTALL,
+    INSTEAD,
     INT,
     INT128,
     INT16,
@@ -683,6 +685,7 @@ define_keywords!(
     STABLE,
     STAGE,
     START,
+    STATEMENT,
     STATIC,
     STATISTICS,
     STATUS,

src/parser/mod.rs

@@ -3368,6 +3368,25 @@ impl<'a> Parser<'a> {
         Ok(values)
     }
 
+    /// Parse a keyword-separated list of 1+ items accepted by `F`
+    pub fn parse_keyword_separated<T, F>(
+        &mut self,
+        keyword: Keyword,
+        mut f: F,
+    ) -> Result<Vec<T>, ParserError>
+    where
+        F: FnMut(&mut Parser<'a>) -> Result<T, ParserError>,
+    {
+        let mut values = vec![];
+        loop {
+            values.push(f(self)?);
+            if !self.parse_keyword(keyword) {
+                break;
+            }
+        }
+        Ok(values)
+    }
+
     pub fn parse_parenthesized<T, F>(&mut self, mut f: F) -> Result<T, ParserError>
     where
         F: FnMut(&mut Parser<'a>) -> Result<T, ParserError>,
@@ -3471,6 +3490,10 @@ impl<'a> Parser<'a> {
             self.parse_create_external_table(or_replace)
         } else if self.parse_keyword(Keyword::FUNCTION) {
             self.parse_create_function(or_replace, temporary)
+        } else if self.parse_keyword(Keyword::TRIGGER) {
+            self.parse_create_trigger(or_replace, false)
+        } else if self.parse_keywords(&[Keyword::CONSTRAINT, Keyword::TRIGGER]) {
+            self.parse_create_trigger(or_replace, true)
         } else if self.parse_keyword(Keyword::MACRO) {
             self.parse_create_macro(or_replace, temporary)
         } else if self.parse_keyword(Keyword::SECRET) {
@@ -4061,6 +4084,180 @@ impl<'a> Parser<'a> {
         })
     }
 
+    /// Parse statements of the DropTrigger type such as:
+    ///
+    /// ```sql
+    /// DROP TRIGGER [ IF EXISTS ] name ON table_name [ CASCADE | RESTRICT ]
+    /// ```
+    pub fn parse_drop_trigger(&mut self) -> Result<Statement, ParserError> {
+        if !dialect_of!(self is PostgreSqlDialect | GenericDialect) {
+            self.prev_token();
+            return self.expected("an object type after DROP", self.peek_token());
+        }
+        let if_exists = self.parse_keywords(&[Keyword::IF, Keyword::EXISTS]);
+        let trigger_name = self.parse_object_name(false)?;
+        self.expect_keyword(Keyword::ON)?;
+        let table_name = self.parse_object_name(false)?;
+        let option = self
+            .parse_one_of_keywords(&[Keyword::CASCADE, Keyword::RESTRICT])
+            .map(|keyword| match keyword {
+                Keyword::CASCADE => ReferentialAction::Cascade,
+                Keyword::RESTRICT => ReferentialAction::Restrict,
+                _ => unreachable!(),
+            });
+        Ok(Statement::DropTrigger {
+            if_exists,
+            trigger_name,
+            table_name,
+            option,
+        })
+    }
+
+    pub fn parse_create_trigger(
+        &mut self,
+        or_replace: bool,
+        is_constraint: bool,
+    ) -> Result<Statement, ParserError> {
+        if !dialect_of!(self is PostgreSqlDialect | GenericDialect) {
+            self.prev_token();
+            return self.expected("an object type after CREATE", self.peek_token());
+        }
+
+        let name = self.parse_object_name(false)?;
+        let period = self.parse_trigger_period()?;
+
+        let events = self.parse_keyword_separated(Keyword::OR, Parser::parse_trigger_event)?;
+        self.expect_keyword(Keyword::ON)?;
+        let table_name = self.parse_object_name(false)?;
+
+        let referenced_table_name = if self.parse_keyword(Keyword::FROM) {
+            self.parse_object_name(true).ok()
+        } else {
+            None
+        };
+
+        let characteristics = self.parse_constraint_characteristics()?;
+
+        let mut referencing = vec![];
+        if self.parse_keyword(Keyword::REFERENCING) {
+            while let Some(refer) = self.parse_trigger_referencing()? {
+                referencing.push(refer);
+            }
+        }
+
+        self.expect_keyword(Keyword::FOR)?;
+        let include_each = self.parse_keyword(Keyword::EACH);
+        let trigger_object =
+            match self.expect_one_of_keywords(&[Keyword::ROW, Keyword::STATEMENT])? {
+                Keyword::ROW => TriggerObject::Row,
+                Keyword::STATEMENT => TriggerObject::Statement,
+                _ => unreachable!(),
+            };
+
+        let condition = self
+            .parse_keyword(Keyword::WHEN)
+            .then(|| self.parse_expr())
+            .transpose()?;
+
+        self.expect_keyword(Keyword::EXECUTE)?;
+
+        let exec_body = self.parse_trigger_exec_body()?;
+
+        Ok(Statement::CreateTrigger {
+            or_replace,
+            is_constraint,
+            name,
+            period,
+            events,
+            table_name,
+            referenced_table_name,
+            referencing,
+            trigger_object,
+            include_each,
+            condition,
+            exec_body,
+            characteristics,
+        })
+    }
+
+    pub fn parse_trigger_period(&mut self) -> Result<TriggerPeriod, ParserError> {
+        Ok(
+            match self.expect_one_of_keywords(&[
+                Keyword::BEFORE,
+                Keyword::AFTER,
+                Keyword::INSTEAD,
+            ])? {
+                Keyword::BEFORE => TriggerPeriod::Before,
+                Keyword::AFTER => TriggerPeriod::After,
+                Keyword::INSTEAD => self
+                    .expect_keyword(Keyword::OF)
+                    .map(|_| TriggerPeriod::InsteadOf)?,
+                _ => unreachable!(),
+            },
+        )
+    }
+
+    pub fn parse_trigger_event(&mut self) -> Result<TriggerEvent, ParserError> {
+        Ok(
+            match self.expect_one_of_keywords(&[
+                Keyword::INSERT,
+                Keyword::UPDATE,
+                Keyword::DELETE,
+                Keyword::TRUNCATE,
+            ])? {
+                Keyword::INSERT => TriggerEvent::Insert,
+                Keyword::UPDATE => {
+                    if self.parse_keyword(Keyword::OF) {
+                        let cols = self.parse_comma_separated(|ident| {
+                            Parser::parse_identifier(ident, false)
+                        })?;
+                        TriggerEvent::Update(cols)
+                    } else {
+                        TriggerEvent::Update(vec![])
+                    }
+                }
+                Keyword::DELETE => TriggerEvent::Delete,
+                Keyword::TRUNCATE => TriggerEvent::Truncate,
+                _ => unreachable!(),
+            },
+        )
+    }
+
+    pub fn parse_trigger_referencing(&mut self) -> Result<Option<TriggerReferencing>, ParserError> {
+        let refer_type = match self.parse_one_of_keywords(&[Keyword::OLD, Keyword::NEW]) {
+            Some(Keyword::OLD) if self.parse_keyword(Keyword::TABLE) => {
+                TriggerReferencingType::OldTable
+            }
+            Some(Keyword::NEW) if self.parse_keyword(Keyword::TABLE) => {
+                TriggerReferencingType::NewTable
+            }
+            _ => {
+                return Ok(None);
+            }
+        };
+
+        let is_as = self.parse_keyword(Keyword::AS);
+        let transition_relation_name = self.parse_object_name(false)?;
+        Ok(Some(TriggerReferencing {
+            refer_type,
+            is_as,
+            transition_relation_name,
+        }))
+    }
+
+    pub fn parse_trigger_exec_body(&mut self) -> Result<TriggerExecBody, ParserError> {
+        Ok(TriggerExecBody {
+            exec_type: match self
+                .expect_one_of_keywords(&[Keyword::FUNCTION, Keyword::PROCEDURE])?
+            {
+                Keyword::FUNCTION => TriggerExecBodyType::Function,
+                Keyword::PROCEDURE => TriggerExecBodyType::Procedure,
+                _ => unreachable!(),
+            },
+            func_desc: self.parse_function_desc()?,
+        })
+    }
+
     pub fn parse_create_macro(
         &mut self,
         or_replace: bool,
@@ -4509,9 +4706,11 @@ impl<'a> Parser<'a> {
             return self.parse_drop_procedure();
         } else if self.parse_keyword(Keyword::SECRET) {
             return self.parse_drop_secret(temporary, persistent);
+        } else if self.parse_keyword(Keyword::TRIGGER) {
+            return self.parse_drop_trigger();
         } else {
             return self.expected(
-                "TABLE, VIEW, INDEX, ROLE, SCHEMA, FUNCTION, PROCEDURE, STAGE or SEQUENCE after DROP",
+                "TABLE, VIEW, INDEX, ROLE, SCHEMA, FUNCTION, PROCEDURE, STAGE, TRIGGER, SECRET or SEQUENCE after DROP",
                 self.peek_token(),
             );
         };
@@ -4550,7 +4749,7 @@ impl<'a> Parser<'a> {
     /// ```
     fn parse_drop_function(&mut self) -> Result<Statement, ParserError> {
         let if_exists = self.parse_keywords(&[Keyword::IF, Keyword::EXISTS]);
-        let func_desc = self.parse_comma_separated(Parser::parse_drop_function_desc)?;
+        let func_desc = self.parse_comma_separated(Parser::parse_function_desc)?;
         let option = match self.parse_one_of_keywords(&[Keyword::CASCADE, Keyword::RESTRICT]) {
             Some(Keyword::CASCADE) => Some(ReferentialAction::Cascade),
             Some(Keyword::RESTRICT) => Some(ReferentialAction::Restrict),
@@ -4569,7 +4768,7 @@ impl<'a> Parser<'a> {
     /// ```
     fn parse_drop_procedure(&mut self) -> Result<Statement, ParserError> {
         let if_exists = self.parse_keywords(&[Keyword::IF, Keyword::EXISTS]);
-        let proc_desc = self.parse_comma_separated(Parser::parse_drop_function_desc)?;
+        let proc_desc = self.parse_comma_separated(Parser::parse_function_desc)?;
         let option = match self.parse_one_of_keywords(&[Keyword::CASCADE, Keyword::RESTRICT]) {
             Some(Keyword::CASCADE) => Some(ReferentialAction::Cascade),
             Some(Keyword::RESTRICT) => Some(ReferentialAction::Restrict),
@@ -4583,7 +4782,7 @@ impl<'a> Parser<'a> {
         })
     }
 
-    fn parse_drop_function_desc(&mut self) -> Result<DropFunctionDesc, ParserError> {
+    fn parse_function_desc(&mut self) -> Result<FunctionDesc, ParserError> {
         let name = self.parse_object_name(false)?;
 
         let args = if self.consume_token(&Token::LParen) {
@@ -4598,7 +4797,7 @@ impl<'a> Parser<'a> {
             None
         };
 
-        Ok(DropFunctionDesc { name, args })
+        Ok(FunctionDesc { name, args })
     }
 
     /// See [DuckDB Docs](https://duckdb.org/docs/sql/statements/create_secret.html) for more details.
@@ -5882,11 +6081,7 @@ impl<'a> Parser<'a> {
     pub fn parse_constraint_characteristics(
         &mut self,
     ) -> Result<Option<ConstraintCharacteristics>, ParserError> {
-        let mut cc = ConstraintCharacteristics {
+        let mut cc = ConstraintCharacteristics::default();
-            deferrable: None,
-            initially: None,
-            enforced: None,
-        };
 
         loop {
             if cc.deferrable.is_none() && self.parse_keywords(&[Keyword::NOT, Keyword::DEFERRABLE])
@@ -7285,6 +7480,7 @@ impl<'a> Parser<'a> {
                     let field_defs = self.parse_click_house_tuple_def()?;
                     Ok(DataType::Tuple(field_defs))
                 }
+                Keyword::TRIGGER => Ok(DataType::Trigger),
                 _ => {
                     self.prev_token();
                     let type_name = self.parse_object_name(false)?;

src/test_utils.rs

@@ -124,6 +124,7 @@ impl TestedDialects {
         }
 
         let only_statement = statements.pop().unwrap();
+
         if !canonical.is_empty() {
             assert_eq!(canonical, only_statement.to_string())
         }

tests/sqlparser_postgres.rs

@@ -3623,7 +3623,7 @@ fn parse_drop_function() {
         pg().verified_stmt(sql),
         Statement::DropFunction {
             if_exists: true,
-            func_desc: vec![DropFunctionDesc {
+            func_desc: vec![FunctionDesc {
                 name: ObjectName(vec![Ident {
                     value: "test_func".to_string(),
                     quote_style: None
@@ -3639,7 +3639,7 @@ fn parse_drop_function() {
         pg().verified_stmt(sql),
         Statement::DropFunction {
             if_exists: true,
-            func_desc: vec![DropFunctionDesc {
+            func_desc: vec![FunctionDesc {
                 name: ObjectName(vec![Ident {
                     value: "test_func".to_string(),
                     quote_style: None
@@ -3664,7 +3664,7 @@ fn parse_drop_function() {
         Statement::DropFunction {
             if_exists: true,
             func_desc: vec![
-                DropFunctionDesc {
+                FunctionDesc {
                     name: ObjectName(vec![Ident {
                         value: "test_func1".to_string(),
                         quote_style: None
@@ -3682,7 +3682,7 @@ fn parse_drop_function() {
                         }
                     ]),
                 },
-                DropFunctionDesc {
+                FunctionDesc {
                     name: ObjectName(vec![Ident {
                         value: "test_func2".to_string(),
                         quote_style: None
@@ -3713,7 +3713,7 @@ fn parse_drop_procedure() {
         pg().verified_stmt(sql),
         Statement::DropProcedure {
             if_exists: true,
-            proc_desc: vec![DropFunctionDesc {
+            proc_desc: vec![FunctionDesc {
                 name: ObjectName(vec![Ident {
                     value: "test_proc".to_string(),
                     quote_style: None
@@ -3729,7 +3729,7 @@ fn parse_drop_procedure() {
         pg().verified_stmt(sql),
         Statement::DropProcedure {
             if_exists: true,
-            proc_desc: vec![DropFunctionDesc {
+            proc_desc: vec![FunctionDesc {
                 name: ObjectName(vec![Ident {
                     value: "test_proc".to_string(),
                     quote_style: None
@@ -3754,7 +3754,7 @@ fn parse_drop_procedure() {
         Statement::DropProcedure {
             if_exists: true,
             proc_desc: vec![
-                DropFunctionDesc {
+                FunctionDesc {
                     name: ObjectName(vec![Ident {
                         value: "test_proc1".to_string(),
                         quote_style: None
@@ -3772,7 +3772,7 @@ fn parse_drop_procedure() {
                         }
                     ]),
                 },
-                DropFunctionDesc {
+                FunctionDesc {
                     name: ObjectName(vec![Ident {
                         value: "test_proc2".to_string(),
                         quote_style: None
@@ -4455,6 +4455,478 @@ fn test_escaped_string_literal() {
     }
 }
 
+#[test]
+fn parse_create_simple_before_insert_trigger() {
+    let sql = "CREATE TRIGGER check_insert BEFORE INSERT ON accounts FOR EACH ROW EXECUTE FUNCTION check_account_insert";
+    let expected = Statement::CreateTrigger {
+        or_replace: false,
+        is_constraint: false,
+        name: ObjectName(vec![Ident::new("check_insert")]),
+        period: TriggerPeriod::Before,
+        events: vec![TriggerEvent::Insert],
+        table_name: ObjectName(vec![Ident::new("accounts")]),
+        referenced_table_name: None,
+        referencing: vec![],
+        trigger_object: TriggerObject::Row,
+        include_each: true,
+        condition: None,
+        exec_body: TriggerExecBody {
+            exec_type: TriggerExecBodyType::Function,
+            func_desc: FunctionDesc {
+                name: ObjectName(vec![Ident::new("check_account_insert")]),
+                args: None,
+            },
+        },
+        characteristics: None,
+    };
+
+    assert_eq!(pg().verified_stmt(sql), expected);
+}
+
+#[test]
+fn parse_create_after_update_trigger_with_condition() {
+    let sql = "CREATE TRIGGER check_update AFTER UPDATE ON accounts FOR EACH ROW WHEN (NEW.balance > 10000) EXECUTE FUNCTION check_account_update";
+    let expected = Statement::CreateTrigger {
+        or_replace: false,
+        is_constraint: false,
+        name: ObjectName(vec![Ident::new("check_update")]),
+        period: TriggerPeriod::After,
+        events: vec![TriggerEvent::Update(vec![])],
+        table_name: ObjectName(vec![Ident::new("accounts")]),
+        referenced_table_name: None,
+        referencing: vec![],
+        trigger_object: TriggerObject::Row,
+        include_each: true,
+        condition: Some(Expr::Nested(Box::new(Expr::BinaryOp {
+            left: Box::new(Expr::CompoundIdentifier(vec![
+                Ident::new("NEW"),
+                Ident::new("balance"),
+            ])),
+            op: BinaryOperator::Gt,
+            right: Box::new(Expr::Value(number("10000"))),
+        }))),
+        exec_body: TriggerExecBody {
+            exec_type: TriggerExecBodyType::Function,
+            func_desc: FunctionDesc {
+                name: ObjectName(vec![Ident::new("check_account_update")]),
+                args: None,
+            },
+        },
+        characteristics: None,
+    };
+
+    assert_eq!(pg().verified_stmt(sql), expected);
+}
+
+#[test]
+fn parse_create_instead_of_delete_trigger() {
+    let sql = "CREATE TRIGGER check_delete INSTEAD OF DELETE ON accounts FOR EACH ROW EXECUTE FUNCTION check_account_deletes";
+    let expected = Statement::CreateTrigger {
+        or_replace: false,
+        is_constraint: false,
+        name: ObjectName(vec![Ident::new("check_delete")]),
+        period: TriggerPeriod::InsteadOf,
+        events: vec![TriggerEvent::Delete],
+        table_name: ObjectName(vec![Ident::new("accounts")]),
+        referenced_table_name: None,
+        referencing: vec![],
+        trigger_object: TriggerObject::Row,
+        include_each: true,
+        condition: None,
+        exec_body: TriggerExecBody {
+            exec_type: TriggerExecBodyType::Function,
+            func_desc: FunctionDesc {
+                name: ObjectName(vec![Ident::new("check_account_deletes")]),
+                args: None,
+            },
+        },
+        characteristics: None,
+    };
+
+    assert_eq!(pg().verified_stmt(sql), expected);
+}
+
+#[test]
+fn parse_create_trigger_with_multiple_events_and_deferrable() {
+    let sql = "CREATE CONSTRAINT TRIGGER check_multiple_events BEFORE INSERT OR UPDATE OR DELETE ON accounts DEFERRABLE INITIALLY DEFERRED FOR EACH ROW EXECUTE FUNCTION check_account_changes";
+    let expected = Statement::CreateTrigger {
+        or_replace: false,
+        is_constraint: true,
+        name: ObjectName(vec![Ident::new("check_multiple_events")]),
+        period: TriggerPeriod::Before,
+        events: vec![
+            TriggerEvent::Insert,
+            TriggerEvent::Update(vec![]),
+            TriggerEvent::Delete,
+        ],
+        table_name: ObjectName(vec![Ident::new("accounts")]),
+        referenced_table_name: None,
+        referencing: vec![],
+        trigger_object: TriggerObject::Row,
+        include_each: true,
+        condition: None,
+        exec_body: TriggerExecBody {
+            exec_type: TriggerExecBodyType::Function,
+            func_desc: FunctionDesc {
+                name: ObjectName(vec![Ident::new("check_account_changes")]),
+                args: None,
+            },
+        },
+        characteristics: Some(ConstraintCharacteristics {
+            deferrable: Some(true),
+            initially: Some(DeferrableInitial::Deferred),
+            enforced: None,
+        }),
+    };
+
+    assert_eq!(pg().verified_stmt(sql), expected);
+}
+
+#[test]
+fn parse_create_trigger_with_referencing() {
+    let sql = "CREATE TRIGGER check_referencing BEFORE INSERT ON accounts REFERENCING NEW TABLE AS new_accounts OLD TABLE AS old_accounts FOR EACH ROW EXECUTE FUNCTION check_account_referencing";
+    let expected = Statement::CreateTrigger {
+        or_replace: false,
+        is_constraint: false,
+        name: ObjectName(vec![Ident::new("check_referencing")]),
+        period: TriggerPeriod::Before,
+        events: vec![TriggerEvent::Insert],
+        table_name: ObjectName(vec![Ident::new("accounts")]),
+        referenced_table_name: None,
+        referencing: vec![
+            TriggerReferencing {
+                refer_type: TriggerReferencingType::NewTable,
+                is_as: true,
+                transition_relation_name: ObjectName(vec![Ident::new("new_accounts")]),
+            },
+            TriggerReferencing {
+                refer_type: TriggerReferencingType::OldTable,
+                is_as: true,
+                transition_relation_name: ObjectName(vec![Ident::new("old_accounts")]),
+            },
+        ],
+        trigger_object: TriggerObject::Row,
+        include_each: true,
+        condition: None,
+        exec_body: TriggerExecBody {
+            exec_type: TriggerExecBodyType::Function,
+            func_desc: FunctionDesc {
+                name: ObjectName(vec![Ident::new("check_account_referencing")]),
+                args: None,
+            },
+        },
+        characteristics: None,
+    };
+
+    assert_eq!(pg().verified_stmt(sql), expected);
+}
+
+#[test]
+/// While in the parse_create_trigger test we test the full syntax of the CREATE TRIGGER statement,
+/// here we test the invalid cases of the CREATE TRIGGER statement which should cause an appropriate
+/// error to be returned.
+fn parse_create_trigger_invalid_cases() {
+    // Test invalid cases for the CREATE TRIGGER statement
+    let invalid_cases = vec![
+        (
+            "CREATE TRIGGER check_update BEFORE UPDATE ON accounts FUNCTION check_account_update",
+            "Expected: FOR, found: FUNCTION"
+        ),
+        (
+            "CREATE TRIGGER check_update TOMORROW UPDATE ON accounts EXECUTE FUNCTION check_account_update",
+            "Expected: one of BEFORE or AFTER or INSTEAD, found: TOMORROW"
+        ),
+        (
+            "CREATE TRIGGER check_update BEFORE SAVE ON accounts EXECUTE FUNCTION check_account_update",
+            "Expected: one of INSERT or UPDATE or DELETE or TRUNCATE, found: SAVE"
+        )
+    ];
+
+    for (sql, expected_error) in invalid_cases {
+        let res = pg().parse_sql_statements(sql);
+        assert_eq!(
+            format!("sql parser error: {expected_error}"),
+            res.unwrap_err().to_string()
+        );
+    }
+}
+
+#[test]
+fn parse_drop_trigger() {
+    for if_exists in [true, false] {
+        for option in [
+            None,
+            Some(ReferentialAction::Cascade),
+            Some(ReferentialAction::Restrict),
+        ] {
+            let sql = &format!(
+                "DROP TRIGGER{} check_update ON table_name{}",
+                if if_exists { " IF EXISTS" } else { "" },
+                option
+                    .map(|o| format!(" {}", o))
+                    .unwrap_or_else(|| "".to_string())
+            );
+            assert_eq!(
+                pg().verified_stmt(sql),
+                Statement::DropTrigger {
+                    if_exists,
+                    trigger_name: ObjectName(vec![Ident::new("check_update")]),
+                    table_name: ObjectName(vec![Ident::new("table_name")]),
+                    option
+                }
+            );
+        }
+    }
+}
+
+#[test]
+fn parse_drop_trigger_invalid_cases() {
+    // Test invalid cases for the DROP TRIGGER statement
+    let invalid_cases = vec![
+        (
+            "DROP TRIGGER check_update ON table_name CASCADE RESTRICT",
+            "Expected: end of statement, found: RESTRICT",
+        ),
+        (
+            "DROP TRIGGER check_update ON table_name CASCADE CASCADE",
+            "Expected: end of statement, found: CASCADE",
+        ),
+        (
+            "DROP TRIGGER check_update ON table_name CASCADE CASCADE CASCADE",
+            "Expected: end of statement, found: CASCADE",
+        ),
+    ];
+
+    for (sql, expected_error) in invalid_cases {
+        let res = pg().parse_sql_statements(sql);
+        assert_eq!(
+            format!("sql parser error: {expected_error}"),
+            res.unwrap_err().to_string()
+        );
+    }
+}
+
+#[test]
+fn parse_trigger_related_functions() {
+    // First we define all parts of the trigger definition,
+    // including the table creation, the function creation, the trigger creation and the trigger drop.
+    // The following example is taken from the PostgreSQL documentation <https://www.postgresql.org/docs/current/plpgsql-trigger.html>
+
+    let sql_table_creation = r#"
+    CREATE TABLE emp (
+        empname           text,
+        salary            integer,
+        last_date         timestamp,
+        last_user         text
+    );
+    "#;
+
+    let sql_create_function = r#"
+    CREATE FUNCTION emp_stamp() RETURNS trigger AS $emp_stamp$
+        BEGIN
+            -- Check that empname and salary are given
+            IF NEW.empname IS NULL THEN
+                RAISE EXCEPTION 'empname cannot be null';
+            END IF;
+            IF NEW.salary IS NULL THEN
+                RAISE EXCEPTION '% cannot have null salary', NEW.empname;
+            END IF;
+    
+            -- Who works for us when they must pay for it?
+            IF NEW.salary < 0 THEN
+                RAISE EXCEPTION '% cannot have a negative salary', NEW.empname;
+            END IF;
+    
+            -- Remember who changed the payroll when
+            NEW.last_date := current_timestamp;
+            NEW.last_user := current_user;
+            RETURN NEW;
+        END;
+    $emp_stamp$ LANGUAGE plpgsql;
+    "#;
+
+    let sql_create_trigger = r#"
+    CREATE TRIGGER emp_stamp BEFORE INSERT OR UPDATE ON emp
+        FOR EACH ROW EXECUTE FUNCTION emp_stamp();
+    "#;
+
+    let sql_drop_trigger = r#"
+    DROP TRIGGER emp_stamp ON emp;
+    "#;
+
+    // Now we parse the statements and check if they are parsed correctly.
+    let mut statements = pg()
+        .parse_sql_statements(&format!(
+            "{}{}{}{}",
+            sql_table_creation, sql_create_function, sql_create_trigger, sql_drop_trigger
+        ))
+        .unwrap();
+
+    assert_eq!(statements.len(), 4);
+    let drop_trigger = statements.pop().unwrap();
+    let create_trigger = statements.pop().unwrap();
+    let create_function = statements.pop().unwrap();
+    let create_table = statements.pop().unwrap();
+
+    // Check the first statement
+    let create_table = match create_table {
+        Statement::CreateTable(create_table) => create_table,
+        _ => panic!("Expected CreateTable statement"),
+    };
+
+    assert_eq!(
+        create_table,
+        CreateTable {
+            or_replace: false,
+            temporary: false,
+            external: false,
+            global: None,
+            if_not_exists: false,
+            transient: false,
+            volatile: false,
+            name: ObjectName(vec![Ident::new("emp")]),
+            columns: vec![
+                ColumnDef {
+                    name: "empname".into(),
+                    data_type: DataType::Text,
+                    collation: None,
+                    options: vec![],
+                },
+                ColumnDef {
+                    name: "salary".into(),
+                    data_type: DataType::Integer(None),
+                    collation: None,
+                    options: vec![],
+                },
+                ColumnDef {
+                    name: "last_date".into(),
+                    data_type: DataType::Timestamp(None, TimezoneInfo::None),
+                    collation: None,
+                    options: vec![],
+                },
+                ColumnDef {
+                    name: "last_user".into(),
+                    data_type: DataType::Text,
+                    collation: None,
+                    options: vec![],
+                },
+            ],
+            constraints: vec![],
+            hive_distribution: HiveDistributionStyle::NONE,
+            hive_formats: Some(HiveFormat {
+                row_format: None,
+                serde_properties: None,
+                storage: None,
+                location: None
+            }),
+            table_properties: vec![],
+            with_options: vec![],
+            file_format: None,
+            location: None,
+            query: None,
+            without_rowid: false,
+            like: None,
+            clone: None,
+            engine: None,
+            comment: None,
+            auto_increment_offset: None,
+            default_charset: None,
+            collation: None,
+            on_commit: None,
+            on_cluster: None,
+            primary_key: None,
+            order_by: None,
+            partition_by: None,
+            cluster_by: None,
+            options: None,
+            strict: false,
+            copy_grants: false,
+            enable_schema_evolution: None,
+            change_tracking: None,
+            data_retention_time_in_days: None,
+            max_data_extension_time_in_days: None,
+            default_ddl_collation: None,
+            with_aggregation_policy: None,
+            with_row_access_policy: None,
+            with_tags: None,
+        }
+    );
+
+    // Check the second statement
+
+    assert_eq!(
+        create_function,
+        Statement::CreateFunction {
+            or_replace: false,
+            temporary: false,
+            if_not_exists: false,
+            name: ObjectName(vec![Ident::new("emp_stamp")]),
+            args: None,
+            return_type: Some(DataType::Trigger),
+            function_body: Some(
+                CreateFunctionBody::AsBeforeOptions(
+                    Expr::Value(
+                        Value::DollarQuotedString(
+                            DollarQuotedString {
+                                value: "\n        BEGIN\n            -- Check that empname and salary are given\n            IF NEW.empname IS NULL THEN\n                RAISE EXCEPTION 'empname cannot be null';\n            END IF;\n            IF NEW.salary IS NULL THEN\n                RAISE EXCEPTION '% cannot have null salary', NEW.empname;\n            END IF;\n    \n            -- Who works for us when they must pay for it?\n            IF NEW.salary < 0 THEN\n                RAISE EXCEPTION '% cannot have a negative salary', NEW.empname;\n            END IF;\n    \n            -- Remember who changed the payroll when\n            NEW.last_date := current_timestamp;\n            NEW.last_user := current_user;\n            RETURN NEW;\n        END;\n    ".to_owned(),
+                                tag: Some(
+                                    "emp_stamp".to_owned(),
+                                ),
+                            },
+                        ),
+                    ),
+                ),
+            ),
+            behavior: None,
+            called_on_null: None,
+            parallel: None,
+            using: None,
+            language: Some(Ident::new("plpgsql")),
+            determinism_specifier: None,
+            options: None,
+            remote_connection: None
+        }
+    );
+
+    // Check the third statement
+
+    assert_eq!(
+        create_trigger,
+        Statement::CreateTrigger {
+            or_replace: false,
+            is_constraint: false,
+            name: ObjectName(vec![Ident::new("emp_stamp")]),
+            period: TriggerPeriod::Before,
+            events: vec![TriggerEvent::Insert, TriggerEvent::Update(vec![])],
+            table_name: ObjectName(vec![Ident::new("emp")]),
+            referenced_table_name: None,
+            referencing: vec![],
+            trigger_object: TriggerObject::Row,
+            include_each: true,
+            condition: None,
+            exec_body: TriggerExecBody {
+                exec_type: TriggerExecBodyType::Function,
+                func_desc: FunctionDesc {
+                    name: ObjectName(vec![Ident::new("emp_stamp")]),
+                    args: None,
+                }
+            },
+            characteristics: None
+        }
+    );
+
+    // Check the fourth statement
+    assert_eq!(
+        drop_trigger,
+        Statement::DropTrigger {
+            if_exists: false,
+            trigger_name: ObjectName(vec![Ident::new("emp_stamp")]),
+            table_name: ObjectName(vec![Ident::new("emp")]),
+            option: None
+        }
+    );
+}
+
 #[test]
 fn test_unicode_string_literal() {
     let pairs = [