feat: reuse NOT NULL constraints for PostgreSQL column definitions (#2696)

Signed-off-by: minleejae <mmj9808@gmail.com>

Author: minleejae

src/main/java/net/sf/jsqlparser/statement/create/table/NotNullConstraint.java

@@ -13,15 +13,30 @@
 import net.sf.jsqlparser.expression.Expression;
 import net.sf.jsqlparser.schema.Column;
 
-/** PostgreSQL 18 table-level NOT NULL constraint, optionally named and non-inheritable. */
+/** PostgreSQL 18 column- or table-level NOT NULL constraint. */
 public class NotNullConstraint extends NamedConstraint {
     private Column column;
     private boolean noInherit;
+    private boolean columnConstraint;
 
     public NotNullConstraint() {
         setType("NOT NULL");
     }
 
+    /** Whether the target is implicit in the enclosing column definition. */
+    public boolean isColumnConstraint() {
+        return columnConstraint;
+    }
+
+    public void setColumnConstraint(boolean columnConstraint) {
+        this.columnConstraint = columnConstraint;
+    }
+
+    public NotNullConstraint withColumnConstraint(boolean columnConstraint) {
+        setColumnConstraint(columnConstraint);
+        return this;
+    }
+
     public Column getColumn() {
         return column;
     }
@@ -61,12 +76,15 @@ public NotNullConstraint withConstraintAttributes(ConstraintAttributes attribute
 
     @Override
     public void appendTo(StringBuilder sql, Consumer<Expression> expressionPrinter) {
-        if (column == null) {
+        if (!columnConstraint && column == null) {
             throw new IllegalStateException("NOT NULL requires a target column");
         }
         appendConstraintPrefixTo(sql);
-        sql.append("NOT NULL ");
-        expressionPrinter.accept(column);
+        sql.append("NOT NULL");
+        if (!columnConstraint) {
+            sql.append(' ');
+            expressionPrinter.accept(column);
+        }
         if (noInherit) {
             sql.append(" NO INHERIT");
         }

src/main/jjtree/net/sf/jsqlparser/parser/JSqlParserCC.jjt

@@ -14138,6 +14138,11 @@ ColumnOption ColumnDefinitionOption(): {
                 || (getToken(1).kind == K_AS && "(".equals(getToken(2).image)) })
         generated=GeneratedColumnDefinition() { option = ColumnOption.generated(generated); }
         |
+        LOOKAHEAD([ <K_CONSTRAINT> RelObjectName() ] <K_NOT> <K_NULL>,
+                { Dialect.POSTGRESQL.name().equals(getAsString(Feature.dialect))
+                    && (getToken(1).kind == K_CONSTRAINT || getToken(3).kind == K_NO) })
+        constraint=PostgreSqlColumnNotNullConstraint() { option = ColumnOption.constraint(constraint); }
+        |
         LOOKAHEAD(<K_NOT> <K_NULL>) <K_NOT> <K_NULL> { option = ColumnOption.nullability(false); }
         |
         LOOKAHEAD(<K_NULL>) <K_NULL> { option = ColumnOption.nullability(true); }
@@ -14958,14 +14963,29 @@ Index TableConstraint(boolean createContext):
 
 /** PostgreSQL 18 adds a table-level NOT NULL with a named target column. */
 NotNullConstraint PostgreSqlNotNullConstraint():
-{ NotNullConstraint constraint = new NotNullConstraint(); String name; }
+{ NotNullConstraint constraint = new NotNullConstraint(); String name; boolean noInherit; }
 {
     <K_NOT> <K_NULL> name=RelObjectName() { constraint.setColumn(createColumn(name)); }
-    [ LOOKAHEAD({ getToken(1).kind == K_NO && "INHERIT".equalsIgnoreCase(getToken(2).image) })
-        <K_NO> TypeDdlKeyword("INHERIT") { constraint.setNoInherit(true); } ]
+    noInherit=PostgreSqlNoInheritClause() { constraint.setNoInherit(noInherit); }
     { return constraint; }
 }
 
+NotNullConstraint PostgreSqlColumnNotNullConstraint():
+{ String name = null; boolean noInherit; }
+{
+    [ <K_CONSTRAINT> name=RelObjectName() ]
+    <K_NOT> <K_NULL> noInherit=PostgreSqlNoInheritClause()
+    { return new NotNullConstraint().withColumnConstraint(true).withName(name).withNoInherit(noInherit); }
+}
+
+boolean PostgreSqlNoInheritClause():
+{ boolean noInherit = false; }
+{
+    [ LOOKAHEAD({ getToken(1).kind == K_NO && "INHERIT".equalsIgnoreCase(getToken(2).image) })
+        <K_NO> TypeDdlKeyword("INHERIT") { noInherit = true; } ]
+    { return noInherit; }
+}
+
 ExcludeConstraint PostgreSqlExcludeConstraint():
 {
     ExcludeConstraint constraint = new ExcludeConstraint();

src/test/java/net/sf/jsqlparser/statement/create/PostgreSqlColumnNotNullTest.java

@@ -0,0 +1,99 @@
+/*-
+ * #%L
+ * JSQLParser library
+ * %%
+ * Copyright (C) 2004 - 2026 JSQLParser
+ * %%
+ * Dual licensed under GNU LGPL 2.1 or Apache License 2.0
+ * #L%
+ */
+package net.sf.jsqlparser.statement.create;
+
+import static org.junit.jupiter.api.Assertions.*;
+import java.util.ArrayList;
+import java.util.List;
+import net.sf.jsqlparser.JSQLParserException;
+import net.sf.jsqlparser.expression.Expression;
+import net.sf.jsqlparser.parser.CCJSqlParserUtil;
+import net.sf.jsqlparser.parser.AbstractJSqlParser.Dialect;
+import net.sf.jsqlparser.statement.Statement;
+import net.sf.jsqlparser.statement.alter.Alter;
+import net.sf.jsqlparser.statement.create.table.ColumnDefinition;
+import net.sf.jsqlparser.statement.create.table.ColumnOption;
+import net.sf.jsqlparser.statement.create.table.CreateTable;
+import net.sf.jsqlparser.statement.create.table.NotNullConstraint;
+import net.sf.jsqlparser.util.TableDefinitionTraversal;
+import net.sf.jsqlparser.util.deparser.StatementDeParser;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.ValueSource;
+
+class PostgreSqlColumnNotNullTest {
+    @ParameterizedTest
+    @ValueSource(strings = {"NOT NULL NO INHERIT", "CONSTRAINT nn NOT NULL",
+            "CONSTRAINT nn NOT NULL NO INHERIT", "CONSTRAINT \"Named NN\" NOT NULL NO INHERIT"})
+    void reusesNotNullConstraintsInCreateAndAlterColumns(String clause) throws JSQLParserException {
+        for (String prefix : List.of("CREATE TABLE t (", "ALTER TABLE t ADD COLUMN ")) {
+            Statement statement = parse(prefix + "id INT " + clause + " DEFAULT 7"
+                    + (prefix.startsWith("CREATE") ? ", value INT)" : ", ADD COLUMN value INT"));
+            ColumnDefinition column = column(statement);
+            NotNullConstraint constraint = assertInstanceOf(NotNullConstraint.class,
+                    column.getColumnOptions().get(0).getConstraint());
+            assertTrue(constraint.isColumnConstraint());
+            assertNull(constraint.getColumn());
+            assertEquals(clause.endsWith("NO INHERIT"), constraint.isNoInherit());
+            assertEquals(ColumnOption.Kind.DEFAULT, column.getColumnOptions().get(1).getKind());
+            roundTrip(statement);
+            constraint.setName("replacement");
+            constraint.setNoInherit(!constraint.isNoInherit());
+            assertTrue(statement.toString().contains("CONSTRAINT replacement NOT NULL"));
+            roundTrip(statement);
+        }
+    }
+
+    @Test
+    void retainsPlainNullabilityAndUsesTheExistingTableModel() throws JSQLParserException {
+        ColumnOption option =
+                column(parse("CREATE TABLE t (id INT NOT NULL)")).getColumnOptions().get(0);
+        assertEquals(ColumnOption.Kind.NULLABILITY, option.getKind());
+        assertEquals(false, option.getNullable());
+        NotNullConstraint table = (NotNullConstraint) ((CreateTable) parse(
+                "CREATE TABLE t (id INT, CONSTRAINT nn NOT NULL id NO INHERIT)")).getIndexes()
+                .get(0);
+        assertFalse(table.isColumnConstraint());
+        assertEquals("id", table.getColumn().getColumnName());
+        assertEquals("CONSTRAINT nn NOT NULL NO INHERIT", new NotNullConstraint()
+                .withColumnConstraint(true).withName("nn").withNoInherit(true).toString());
+    }
+
+    @Test
+    void doesNotInventASecondColumnExpressionForAnImplicitTarget() throws JSQLParserException {
+        CreateTable table =
+                (CreateTable) parse("CREATE TABLE t (id INT DEFAULT 7 NOT NULL NO INHERIT)");
+        List<Expression> expressions = new ArrayList<>();
+        TableDefinitionTraversal.visit(table, expressions::add, t -> {
+        });
+        assertEquals(1, expressions.size());
+        assertEquals("7", expressions.get(0).toString());
+        roundTrip(table);
+        assertEquals(2, CCJSqlParserUtil.parseStatements(table + "; SELECT 1",
+                p -> p.withDialect(Dialect.POSTGRESQL)).size());
+    }
+
+    private static ColumnDefinition column(Statement statement) {
+        return statement instanceof CreateTable
+                ? ((CreateTable) statement).getColumnDefinitions().get(0)
+                : ((Alter) statement).getAlterExpressions().get(0).getColDataTypeList().get(0);
+    }
+
+    private static Statement parse(String sql) throws JSQLParserException {
+        return CCJSqlParserUtil.parse(sql, p -> p.withDialect(Dialect.POSTGRESQL));
+    }
+
+    private static void roundTrip(Statement statement) throws JSQLParserException {
+        StringBuilder out = new StringBuilder();
+        statement.accept(new StatementDeParser(out));
+        assertEquals(statement.toString(), out.toString());
+        assertEquals(out.toString(), parse(out.toString()).toString());
+    }
+}