Add graph edge CONNECTION constraint parsing with ON DELETE CASCADE

Support for parsing CONNECTION constraints in graph edge tables:
- Named constraints: CONSTRAINT name CONNECTION (N1 TO N2)
- Unnamed constraints: CONNECTION (N1 TO N2)
- ON DELETE CASCADE clause for both named and unnamed
- ALTER TABLE ADD CONSTRAINT CONNECTION with ON DELETE CASCADE

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: kyleconroy

parser/marshal.go

@@ -5410,6 +5410,59 @@ func (p *Parser) parseCreateTableStatement() (*ast.CreateTableStatement, error)
 					return stmt, nil
 				}
 				stmt.Definition.Indexes = append(stmt.Definition.Indexes, indexDef)
+			} else if upperLit == "CONNECTION" {
+				// Parse unnamed CONNECTION constraint for graph edge tables
+				p.nextToken() // consume CONNECTION
+				constraint := &ast.GraphConnectionConstraintDefinition{}
+				if p.curTok.Type == TokenLParen {
+					p.nextToken() // consume (
+					for p.curTok.Type != TokenRParen && p.curTok.Type != TokenEOF {
+						conn := &ast.GraphConnectionBetweenNodes{}
+						// Parse FromNode
+						fromNode, err := p.parseSchemaObjectName()
+						if err != nil {
+							p.skipToEndOfStatement()
+							return stmt, nil
+						}
+						conn.FromNode = fromNode
+						// Expect TO
+						if strings.ToUpper(p.curTok.Literal) == "TO" {
+							p.nextToken() // consume TO
+						}
+						// Parse ToNode
+						toNode, err := p.parseSchemaObjectName()
+						if err != nil {
+							p.skipToEndOfStatement()
+							return stmt, nil
+						}
+						conn.ToNode = toNode
+						constraint.FromNodeToNodeList = append(constraint.FromNodeToNodeList, conn)
+						if p.curTok.Type == TokenComma {
+							p.nextToken()
+						} else {
+							break
+						}
+					}
+					if p.curTok.Type == TokenRParen {
+						p.nextToken() // consume )
+					}
+				}
+				// Check for ON DELETE CASCADE
+				if p.curTok.Type == TokenOn && strings.ToUpper(p.peekTok.Literal) == "DELETE" {
+					p.nextToken() // consume ON
+					p.nextToken() // consume DELETE
+					if strings.ToUpper(p.curTok.Literal) == "CASCADE" {
+						constraint.DeleteAction = "Cascade"
+						p.nextToken() // consume CASCADE
+					} else if strings.ToUpper(p.curTok.Literal) == "NO" {
+						p.nextToken() // consume NO
+						if strings.ToUpper(p.curTok.Literal) == "ACTION" {
+							constraint.DeleteAction = "NoAction"
+							p.nextToken() // consume ACTION
+						}
+					}
+				}
+				stmt.Definition.TableConstraints = append(stmt.Definition.TableConstraints, constraint)
 			} else {
 				// Parse column definition
 				colDef, err := p.parseColumnDefinition()
@@ -8168,6 +8221,22 @@ func (p *Parser) parseConnectionConstraint() (*ast.GraphConnectionConstraintDefi
 		}
 	}
 
+	// Check for ON DELETE CASCADE
+	if p.curTok.Type == TokenOn && strings.ToUpper(p.peekTok.Literal) == "DELETE" {
+		p.nextToken() // consume ON
+		p.nextToken() // consume DELETE
+		if strings.ToUpper(p.curTok.Literal) == "CASCADE" {
+			constraint.DeleteAction = "Cascade"
+			p.nextToken() // consume CASCADE
+		} else if strings.ToUpper(p.curTok.Literal) == "NO" {
+			p.nextToken() // consume NO
+			if strings.ToUpper(p.curTok.Literal) == "ACTION" {
+				constraint.DeleteAction = "NoAction"
+				p.nextToken() // consume ACTION
+			}
+		}
+	}
+
 	return constraint, nil
 }
 

parser/parse_ddl.go

@@ -6384,6 +6384,21 @@ func (p *Parser) parseAlterTableAddStatement(tableName *ast.SchemaObjectName) (*
 					p.nextToken() // consume )
 				}
 			}
+			// Check for ON DELETE CASCADE
+			if p.curTok.Type == TokenOn && strings.ToUpper(p.peekTok.Literal) == "DELETE" {
+				p.nextToken() // consume ON
+				p.nextToken() // consume DELETE
+				if strings.ToUpper(p.curTok.Literal) == "CASCADE" {
+					constraint.DeleteAction = "Cascade"
+					p.nextToken() // consume CASCADE
+				} else if strings.ToUpper(p.curTok.Literal) == "NO" {
+					p.nextToken() // consume NO
+					if strings.ToUpper(p.curTok.Literal) == "ACTION" {
+						constraint.DeleteAction = "NoAction"
+						p.nextToken() // consume ACTION
+					}
+				}
+			}
 			stmt.Definition.TableConstraints = append(stmt.Definition.TableConstraints, constraint)
 
 		case "DEFAULT":

parser/testdata/Baselines150_GraphDbEdgeConstraintsSyntaxTests150/metadata.json

@@ -1 +1 @@
-{"todo": true}
+{}

parser/testdata/GraphDbEdgeConstraintsSyntaxTests150/metadata.json

@@ -1 +1 @@
-{"todo": true}
+{}