Share access to table and view column defaults

src/main/java/net/sf/jsqlparser/statement/alter/AlterExpression.java

@@ -419,6 +419,20 @@ public List<ColumnSetDefault> getColumnSetDefaultList() {
         return columnSetDefaultList;
     }
 
+    /**
+     * Returns this action's active SET DEFAULT entries through the same API used by ALTER VIEW. The
+     * list is read-only; its entries are the original mutable AST objects, not copies. Use the
+     * existing action-specific API to add or remove entries.
+     */
+    public List<ColumnDefaultAction> getColumnDefaults() {
+        if (operation != AlterOperation.ALTER || columnSetDefaultList == null
+                || constraintType != null && constraintSymbol != null
+                || columnDropDefaultList != null && !columnDropDefaultList.isEmpty()) {
+            return Collections.emptyList();
+        }
+        return Collections.unmodifiableList(columnSetDefaultList);
+    }
+
     public void addColSetVisibility(ColumnSetVisibility columnSetVisibility) {
         if (columnSetVisibilityList == null) {
             columnSetVisibilityList = new ArrayList<>();
@@ -1696,8 +1710,8 @@ public String toString() {
         }
     }
 
-    public static final class ColumnSetDefault implements Serializable {
-        private final String columnName;
+    public static final class ColumnSetDefault implements ColumnDefaultAction, Serializable {
+        private String columnName;
         private String defaultValue;
         private Expression defaultExpression;
 
@@ -1706,37 +1720,42 @@ public ColumnSetDefault(String columnName, String defaultValue) {
             this.defaultValue = defaultValue;
         }
 
+        @Override
         public String getColumnName() {
             return columnName;
         }
 
+        @Override
+        public void setColumnName(String columnName) {
+            this.columnName = columnName;
+        }
+
         /** Constructs a structured default without overloading the legacy nullable String API. */
         public static ColumnSetDefault fromExpression(String columnName, Expression expression) {
             ColumnSetDefault result = new ColumnSetDefault(columnName, null);
             result.setDefaultExpression(expression);
             return result;
         }
 
+        @Override
         public Expression getDefaultExpression() {
             return defaultExpression;
         }
 
+        @Override
         public void setDefaultExpression(Expression defaultExpression) {
             this.defaultExpression = defaultExpression;
             this.defaultValue = null;
         }
 
+        @Override
         public String getDefaultValue() {
             return defaultExpression == null ? defaultValue : defaultExpression.toString();
         }
 
         public void appendTo(StringBuilder sql, Consumer<Expression> expressionPrinter) {
             sql.append(columnName).append(" SET DEFAULT ");
-            if (defaultExpression == null) {
-                sql.append(defaultValue);
-            } else {
-                expressionPrinter.accept(defaultExpression);
-            }
+            appendDefaultValueTo(sql, expressionPrinter);
         }
 
         @Override

src/main/java/net/sf/jsqlparser/statement/alter/ColumnDefaultAction.java

@@ -0,0 +1,45 @@
+/*-
+ * #%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.alter;
+
+import java.util.function.Consumer;
+import net.sf.jsqlparser.expression.Expression;
+
+/**
+ * Shared access to a column SET DEFAULT action on a table or view. Obtain active actions through
+ * {@link AlterExpression#getColumnDefaults()}; edits update the existing statement model directly.
+ */
+public interface ColumnDefaultAction {
+    String getColumnName();
+
+    void setColumnName(String columnName);
+
+    /** Returns the parsed default, or null for a legacy opaque SQL value. */
+    Expression getDefaultExpression();
+
+    /** Replaces the default expression, discarding any legacy opaque SQL value. */
+    void setDefaultExpression(Expression expression);
+
+    /** Returns the default's SQL text, including legacy opaque values when present. */
+    default String getDefaultValue() {
+        Expression expression = getDefaultExpression();
+        return expression == null ? null : expression.toString();
+    }
+
+    /** Renders the shared value while preserving the caller's expression visitor. */
+    default void appendDefaultValueTo(StringBuilder sql, Consumer<Expression> expressionPrinter) {
+        Expression expression = getDefaultExpression();
+        if (expression == null) {
+            sql.append(getDefaultValue());
+        } else {
+            expressionPrinter.accept(expression);
+        }
+    }
+}

src/main/java/net/sf/jsqlparser/statement/alter/RelationAlterAction.java

@@ -9,6 +9,7 @@
  */
 package net.sf.jsqlparser.statement.alter;
 
+import java.util.Collections;
 import java.util.List;
 import java.util.function.Consumer;
 import net.sf.jsqlparser.expression.Expression;
@@ -17,7 +18,7 @@
 import net.sf.jsqlparser.statement.select.PlainSelect;
 
 /** Structured PostgreSQL property actions shared by tables, indexes and views. */
-public class RelationAlterAction extends AlterExpression {
+public class RelationAlterAction extends AlterExpression implements ColumnDefaultAction {
     private EnableState enableState;
     private TriggerTarget triggerTarget;
     private Kind kind;
@@ -168,14 +169,23 @@ public void setStatisticsDefault(boolean statisticsDefault) {
         }
     }
 
+    @Override
     public Expression getDefaultExpression() {
         return defaultExpression;
     }
 
+    @Override
     public void setDefaultExpression(Expression defaultExpression) {
         this.defaultExpression = defaultExpression;
     }
 
+    @Override
+    public List<ColumnDefaultAction> getColumnDefaults() {
+        return kind == Kind.ALTER_COLUMN && columnAction == ColumnAction.SET_DEFAULT
+                ? Collections.singletonList(this)
+                : Collections.emptyList();
+    }
+
     public Table getRelation() {
         return relation;
     }
@@ -315,7 +325,7 @@ private void appendColumnChange(StringBuilder builder, Consumer<Expression> expr
         switch (columnAction) {
             case SET_DEFAULT:
                 builder.append(" SET DEFAULT ");
-                expressionPrinter.accept(defaultExpression);
+                appendDefaultValueTo(builder, expressionPrinter);
                 break;
             case DROP_DEFAULT:
                 builder.append(" DROP DEFAULT");

src/main/java/net/sf/jsqlparser/util/deparser/AlterDeParser.java

@@ -84,9 +84,7 @@ private void deParseAction(AlterExpression action) {
             deParseTail(action);
             return;
         }
-        if (action.getOperation() == net.sf.jsqlparser.statement.alter.AlterOperation.ALTER
-                && action.getColumnSetDefaultList() != null
-                && !action.getColumnSetDefaultList().isEmpty()) {
+        if (!action.getColumnDefaults().isEmpty()) {
             action.appendColumnActionTo(builder,
                     expression -> expression.accept(expressionVisitor, null));
             return;

src/site/sphinx/usage.rst

@@ -346,6 +346,37 @@ bare ``RESTART``, which uses the sequence's configured start value. Call
 ``new IdentityAlteration(Kind.RESTART).withRestartWith(20L)``.
 
 
+Column defaults on tables and views
+-----------------------------------
+
+``AlterExpression.getColumnDefaults()`` exposes active ``SET DEFAULT`` actions
+through ``ColumnDefaultAction`` for both tables and views. The returned list is
+read-only, but its entries are the original mutable AST objects:
+
+.. code-block:: java
+
+    for (String objectType : List.of("TABLE", "VIEW")) {
+        Statement statement = CCJSqlParserUtil.parse(
+                "ALTER " + objectType + " t ALTER COLUMN a SET DEFAULT 1",
+                parser -> parser.withDialect(Dialect.POSTGRESQL));
+        List<? extends AlterExpression> actions = statement instanceof Alter
+                ? ((Alter) statement).getAlterExpressions()
+                : ((AlterRelation) statement).getActions();
+        for (AlterExpression action : actions) {
+            for (ColumnDefaultAction column : action.getColumnDefaults()) {
+                column.setDefaultExpression(new LongValue(42));
+            }
+        }
+        System.out.println(statement); // SET DEFAULT 42 for either object type
+    }
+
+``getColumnName()`` and ``setColumnName()`` access the affected column.
+``getDefaultExpression()`` exposes parsed expressions; ``getDefaultValue()``
+returns their SQL text. Existing ``ColumnSetDefault`` constructors still accept
+opaque strings, for which ``getDefaultExpression()`` returns ``null``.
+Replacing an expression also replaces any opaque value. Unrelated actions
+return an empty list.
+
 Structured column attributes
 ============================