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feat: preserve ALTER COLUMN default expressions in the AST #2611

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Merged
manticore-projects merged 2 commits into from
Sep 12, 2026
Merged

feat: preserve ALTER COLUMN default expressions in the AST #2611

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36b26d2
feat: preserve ALTER COLUMN default expressions in the AST
minleejae Sep 12, 2026
a42f1c1
refactor: group default rendering with column action dispatch
minleejae Sep 12, 2026
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52 changes: 48 additions & 4 deletions src/main/java/net/sf/jsqlparser/statement/alter/AlterExpression.java
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Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,7 @@
import java.util.List;
import java.util.Optional;
import java.util.Set;
import java.util.function.Consumer;
import java.util.stream.Collectors;
import net.sf.jsqlparser.expression.Expression;
import net.sf.jsqlparser.statement.ReferentialAction;
Expand Down Expand Up @@ -883,14 +884,29 @@ protected void toStringConstraintAlter(StringBuilder b) {
}

protected void toStringAlterColumn(StringBuilder b) {
appendAlterColumn(b, b::append);
}

/** Renders ALTER COLUMN default/visibility actions with their common tail. */
public void appendColumnActionTo(StringBuilder b, Consumer<Expression> expressionPrinter) {
appendAlterColumn(b, expressionPrinter);
appendCommonTail(b);
}

private void appendAlterColumn(StringBuilder b, Consumer<Expression> expressionPrinter) {
b.append("ALTER ");
if (hasColumn) {
b.append("COLUMN ");
}
if (columnDropDefaultList != null && !columnDropDefaultList.isEmpty()) {
b.append(PlainSelect.getStringList(columnDropDefaultList));
} else if (columnSetDefaultList != null && !columnSetDefaultList.isEmpty()) {
b.append(PlainSelect.getStringList(columnSetDefaultList));
for (int i = 0; i < columnSetDefaultList.size(); i++) {
if (i > 0) {
b.append(", ");
}
columnSetDefaultList.get(i).appendTo(b, expressionPrinter);
}
} else {
b.append(PlainSelect.getStringList(columnSetVisibilityList));
}
Expand Down Expand Up @@ -1575,7 +1591,8 @@ public String toString() {

public static final class ColumnSetDefault implements Serializable {
private final String columnName;
private final String defaultValue;
private String defaultValue;
private Expression defaultExpression;

public ColumnSetDefault(String columnName, String defaultValue) {
this.columnName = columnName;
Expand All @@ -1586,13 +1603,40 @@ public String getColumnName() {
return 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;
}

public Expression getDefaultExpression() {
return defaultExpression;
}

public void setDefaultExpression(Expression defaultExpression) {
this.defaultExpression = defaultExpression;
this.defaultValue = null;
}

public String getDefaultValue() {
return defaultValue;
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);
}
}

@Override
public String toString() {
return columnName + " SET DEFAULT " + defaultValue;
StringBuilder sql = new StringBuilder();
appendTo(sql, sql::append);
return sql.toString();
}
}

Expand Down
4 changes: 4 additions & 0 deletions src/main/java/net/sf/jsqlparser/util/TableDefinitionTraversal.java
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Expand Up @@ -44,6 +44,10 @@ public static void visit(CreateIndex createIndex, Consumer<Expression> expressio
/** Visits the structured definitions and expressions belonging to a single ALTER action. */
public static void visit(AlterExpression action, Consumer<Expression> expressions,
Consumer<Table> tables) {
if (action.getColumnSetDefaultList() != null) {
action.getColumnSetDefaultList()
.forEach(column -> accept(column.getDefaultExpression(), expressions));
}
if (action.getColDataTypeList() != null) {
action.getColDataTypeList().forEach(column -> visit(column, expressions, tables));
}
Expand Down
7 changes: 7 additions & 0 deletions src/main/java/net/sf/jsqlparser/util/deparser/AlterDeParser.java
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Expand Up @@ -60,6 +60,13 @@ private void deParseAction(AlterExpression action) {
deParseTail(action);
return;
}
if (action.getOperation() == net.sf.jsqlparser.statement.alter.AlterOperation.ALTER
&& action.getColumnSetDefaultList() != null
&& !action.getColumnSetDefaultList().isEmpty()) {
action.appendColumnActionTo(builder,
expression -> expression.accept(expressionVisitor, null));
return;
}
if (action.getColDataTypeList() == null || action.getColDataTypeList().size() != 1
|| action.getColDataTypeList().get(0).getUsingExpression() == null) {
builder.append(action);
Expand Down
10 changes: 2 additions & 8 deletions src/main/java/net/sf/jsqlparser/util/validation/validator/AlterValidator.java
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Original file line number Diff line number Diff line change
Expand Up @@ -40,14 +40,8 @@ public void validate(Alter alter) {
}

public void validate(Alter alter, AlterExpression e) {
if (e.getColDataTypeList() != null) {
e.getColDataTypeList().forEach(column -> TableDefinitionTraversal.visit(column,
this::validateOptionalExpression, this::validateOptionalFromItem));
}
if (e.getIndex() != null) {
TableDefinitionTraversal.visit(e.getIndex(), this::validateOptionalExpression,
this::validateOptionalFromItem);
}
TableDefinitionTraversal.visit(e, this::validateOptionalExpression,
this::validateOptionalFromItem);
for (ValidationCapability c : getCapabilities()) {

validateOptionalColumnName(c, e.getColumnOldName());
Expand Down
2 changes: 1 addition & 1 deletion src/main/jjtree/net/sf/jsqlparser/parser/JSqlParserCC.jjt
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Original file line number Diff line number Diff line change
Expand Up @@ -14552,7 +14552,7 @@ AlterExpression.ColumnSetDefault AlterExpressionColumnSetDefault():
{
columnName = RelObjectName() <K_SET> <K_DEFAULT> defaultValue = Expression()
{
return new AlterExpression.ColumnSetDefault(columnName, defaultValue.toString());
return AlterExpression.ColumnSetDefault.fromExpression(columnName, defaultValue);
}
}

Expand Down
101 changes: 101 additions & 0 deletions src/test/java/net/sf/jsqlparser/statement/alter/AlterColumnDefaultExpressionTest.java
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Original file line number Diff line number Diff line change
@@ -0,0 +1,101 @@
/*-
* #%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 static org.assertj.core.api.Assertions.assertThat;
import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertNotNull;
import static org.junit.jupiter.api.Assertions.assertNull;

import java.util.ArrayList;
import java.util.List;
import net.sf.jsqlparser.JSQLParserException;
import net.sf.jsqlparser.expression.ExpressionVisitorAdapter;
import net.sf.jsqlparser.expression.LongValue;
import net.sf.jsqlparser.parser.CCJSqlParserUtil;
import net.sf.jsqlparser.statement.StatementVisitorAdapter;
import net.sf.jsqlparser.statement.alter.AlterExpression.ColumnSetDefault;
import net.sf.jsqlparser.statement.select.SelectVisitorAdapter;
import net.sf.jsqlparser.util.deparser.ExpressionDeParser;
import net.sf.jsqlparser.util.deparser.SelectDeParser;
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 AlterColumnDefaultExpressionTest {
@ParameterizedTest
@ValueSource(strings = {"(1 + 2)", "NULL", "CURRENT_TIMESTAMP",
"nextval('app.counter'::regclass)", "'value'::text", "-1"})
void parsedDefaultRetainsExpressionAndLegacyText(String value) throws JSQLParserException {
Alter alter = parse(value);
ColumnSetDefault column =
alter.getAlterExpressions().get(0).getColumnSetDefaultList().get(0);
assertNotNull(column.getDefaultExpression());
assertEquals(column.getDefaultExpression().toString(), column.getDefaultValue());
StringBuilder buffer = new StringBuilder();
alter.accept(new StatementDeParser(buffer), null);
assertEquals(alter.toString(), buffer.toString());
assertEquals(alter.toString(), CCJSqlParserUtil.parse(buffer.toString()).toString());
}

@Test
void visitorReachesDefaultsInEachAlterActionWithContext() throws JSQLParserException {
List<Long> values = new ArrayList<>();
ExpressionVisitorAdapter<Void> expressions = new ExpressionVisitorAdapter<Void>() {
@Override
public <S> Void visit(LongValue value, S context) {
assertEquals("context", context);
values.add(value.getValue());
return null;
}
};
CCJSqlParserUtil.parse("ALTER TABLE t ALTER COLUMN a SET DEFAULT (1 + 2), "
+ "ALTER COLUMN b SET DEFAULT 3")
.accept(new StatementVisitorAdapter<>(new SelectVisitorAdapter<>(expressions)),
"context");
assertThat(values).containsExactly(1L, 2L, 3L);
}

@Test
void customDeparserAndAstEditsUseTheStructuredDefault() throws JSQLParserException {
Alter alter = parse("(1 + 2)");
StringBuilder output = new StringBuilder();
ExpressionDeParser expressions = new ExpressionDeParser() {
@Override
public <S> StringBuilder visit(LongValue value, S context) {
return getBuilder().append(value.getValue() + 100);
}
};
alter.accept(new StatementDeParser(expressions, new SelectDeParser(), output), null);
assertEquals("ALTER TABLE t ALTER COLUMN a SET DEFAULT (101 + 102)", output.toString());
ColumnSetDefault column =
alter.getAlterExpressions().get(0).getColumnSetDefaultList().get(0);
column.setDefaultExpression(new LongValue(42));
assertEquals("42", column.getDefaultValue());
assertEquals("ALTER TABLE t ALTER COLUMN a SET DEFAULT 42", alter.toString());
}

@Test
void legacyStringConstructorRemainsOpaqueAndAcceptsNull() {
ColumnSetDefault column = new ColumnSetDefault("a", "vendor_default()");
assertNull(column.getDefaultExpression());
assertEquals("a SET DEFAULT vendor_default()", column.toString());
assertEquals("a SET DEFAULT null", new ColumnSetDefault("a", null).toString());
column.setDefaultExpression(new LongValue(1));
assertEquals("1", column.getDefaultValue());
column.setDefaultExpression(null);
assertNull(column.getDefaultValue());
}

private static Alter parse(String value) throws JSQLParserException {
return (Alter) CCJSqlParserUtil.parse("ALTER TABLE t ALTER COLUMN a SET DEFAULT " + value);
}
}
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