add support for default session transaction characteristics

Signed-off-by: poonai <[email protected]>

Author: poonai

src/ast/mod.rs

@@ -786,7 +786,7 @@ pub enum Statement {
     /// `{ BEGIN [ TRANSACTION | WORK ] | START TRANSACTION } ...`
     StartTransaction { modes: Vec<TransactionMode> },
     /// `SET TRANSACTION ...`
-    SetTransaction { modes: Vec<TransactionMode>, snapshot: Option<Value> },
+    SetTransaction { modes: Vec<TransactionMode>, snapshot: Option<Value>, session: bool },
     /// `COMMIT [ TRANSACTION | WORK ] [ AND [ NO ] CHAIN ]`
     Commit { chain: bool },
     /// `ROLLBACK [ TRANSACTION | WORK ] [ AND [ NO ] CHAIN ]`
@@ -1369,8 +1369,12 @@ impl fmt::Display for Statement {
                 }
                 Ok(())
             }
-            Statement::SetTransaction { modes, snapshot } => {
-                write!(f, "SET TRANSACTION")?;
+            Statement::SetTransaction { modes, snapshot, session } => {
+                if *session {
+                    write!(f, "SET SESSION CHARACTERISTICS AS TRANSACTION")?;
+                } else {
+                    write!(f, "SET TRANSACTION")?;
+                }
                 if !modes.is_empty() {
                     write!(f, " {}", display_comma_separated(modes))?;
                 }

src/parser.rs

@@ -2670,17 +2670,26 @@ impl<'a> Parser<'a> {
                     value: values,
                 });
             }
+        } else if variable.value == "CHARACTERISTICS" {
+            self.expect_keywords(&[Keyword::AS, Keyword::TRANSACTION])?;
+            Ok(Statement::SetTransaction {
+                modes: self.parse_transaction_modes()?,
+                snapshot: None,
+                session: true,
+            })
         } else if variable.value == "TRANSACTION" && modifier.is_none() {
-            if self.parse_keyword(Keyword::SNAPSHOT){
+            if self.parse_keyword(Keyword::SNAPSHOT) {
                 let snaphot_id = self.parse_value()?;
-                return Ok(Statement::SetTransaction{
+                return Ok(Statement::SetTransaction {
                     modes: vec![],
-                    snapshot: Some(snaphot_id)
-                })
+                    snapshot: Some(snaphot_id),
+                    session: false
+                });
             }
             Ok(Statement::SetTransaction {
                 modes: self.parse_transaction_modes()?,
-                snapshot: None
+                snapshot: None,
+                session: false
             })
         } else {
             self.expected("equals sign or TO", self.peek_token())

tests/sqlparser_common.rs

@@ -3586,7 +3586,7 @@ fn parse_set_transaction() {
     // TRANSACTION, so no need to duplicate the tests here. We just do a quick
     // sanity check.
     match verified_stmt("SET TRANSACTION READ ONLY, READ WRITE, ISOLATION LEVEL SERIALIZABLE") {
-        Statement::SetTransaction { modes, snapshot:None } => assert_eq!(
+        Statement::SetTransaction { modes, .. } => assert_eq!(
             modes,
             vec![
                 TransactionMode::AccessMode(TransactionAccessMode::ReadOnly),

tests/sqlparser_postgres.rs

@@ -726,10 +726,27 @@ fn parse_map_access_expr() {
 #[test]
 fn test_transaction_statement() {
     let statement = pg().verified_stmt("SET TRANSACTION SNAPSHOT '000003A1-1'");
-    assert_eq!(statement, Statement::SetTransaction{
-        modes: vec![],
-        snapshot: Some(Value::SingleQuotedString(String::from("000003A1-1")))
-    })
+    assert_eq!(
+        statement,
+        Statement::SetTransaction {
+            modes: vec![],
+            snapshot: Some(Value::SingleQuotedString(String::from("000003A1-1"))),
+            session: false
+        }
+    );
+    let statement = pg().verified_stmt("SET SESSION CHARACTERISTICS AS TRANSACTION READ ONLY, READ WRITE, ISOLATION LEVEL SERIALIZABLE");
+    assert_eq!(
+        statement,
+        Statement::SetTransaction {
+            modes: vec![
+                TransactionMode::AccessMode(TransactionAccessMode::ReadOnly),
+                TransactionMode::AccessMode(TransactionAccessMode::ReadWrite),
+                TransactionMode::IsolationLevel(TransactionIsolationLevel::Serializable),
+            ],
+            snapshot: None,
+            session: true
+        }
+    );
 }
 
 fn pg() -> TestedDialects {