fix: model PostgreSQL DROP INDEX CONCURRENTLY

src/main/java/net/sf/jsqlparser/statement/drop/Drop.java

@@ -38,6 +38,22 @@ public enum ObjectType {
     private Map<String, List<String>> typeToParameters = new HashMap<>();
     private boolean ifExists = false;
     private boolean materialized = false;
+    private boolean concurrently;
+
+    /** PostgreSQL DROP INDEX CONCURRENTLY, preceding IF EXISTS and the index name. */
+    public boolean isConcurrently() {
+        return concurrently;
+    }
+
+    public void setConcurrently(boolean concurrently) {
+        this.concurrently = concurrently;
+    }
+
+    public Drop withConcurrently(boolean concurrently) {
+        setConcurrently(concurrently);
+        return this;
+    }
+
 
     private boolean isUsingTemporary;
 
@@ -201,7 +217,11 @@ public StringBuilder appendTo(StringBuilder builder, Consumer<Table> tablePrinte
         if (materialized) {
             builder.append("MATERIALIZED ");
         }
-        builder.append(type).append(ifExists ? " IF EXISTS " : " ");
+        builder.append(type);
+        if (concurrently) {
+            builder.append(" CONCURRENTLY");
+        }
+        builder.append(ifExists ? " IF EXISTS " : " ");
         appendNames(builder, tablePrinter);
         if ("FUNCTION".equals(type)) {
             builder.append(formatFuncParams(getParamsByType("FUNCTION")));

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

@@ -16334,6 +16334,9 @@ Drop Drop():
         tk=<K_FUNCTION>
     )
     { drop.setType(tk.image); }
+    [ LOOKAHEAD({ drop.getObjectType() == Drop.ObjectType.INDEX
+            && getToken(1).kind == K_CONCURRENTLY })
+        <K_CONCURRENTLY> { drop.setConcurrently(true); } ]
 
     [ LOOKAHEAD(2) <K_IF> <K_EXISTS> {drop.setIfExists(true);} ]
 

src/test/java/net/sf/jsqlparser/statement/drop/PostgreSqlDropIndexTest.java

@@ -0,0 +1,56 @@
+/*-
+ * #%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.drop;
+
+import static org.junit.jupiter.api.Assertions.*;
+import net.sf.jsqlparser.JSQLParserException;
+import net.sf.jsqlparser.parser.AbstractJSqlParser.Dialect;
+import net.sf.jsqlparser.parser.CCJSqlParserUtil;
+import net.sf.jsqlparser.schema.Table;
+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 PostgreSqlDropIndexTest {
+    @ParameterizedTest
+    @ValueSource(strings = {"DROP INDEX CONCURRENTLY ix",
+            "DROP INDEX CONCURRENTLY IF EXISTS ix",
+            "DROP INDEX CONCURRENTLY IF EXISTS public.ix RESTRICT"})
+    void concurrencyIsIndependentOfTarget(String sql) throws JSQLParserException {
+        Drop drop = (Drop) CCJSqlParserUtil.parse(sql, p -> p.withDialect(Dialect.POSTGRESQL));
+        assertTrue(drop.isConcurrently());
+        assertEquals(sql.contains("IF EXISTS"), drop.isIfExists());
+        assertEquals("ix", drop.getName().getName());
+        assertEquals(sql, drop.toString());
+        drop.setName(new Table("new_ix"));
+        String expected = sql.replace("public.ix", "ix").replace("ix", "new_ix");
+        assertEquals(expected, drop.toString());
+        StringBuilder buffer = new StringBuilder();
+        drop.accept(new StatementDeParser(buffer), null);
+        assertEquals(expected, buffer.toString());
+        Drop reparsed = (Drop) CCJSqlParserUtil.parse(expected);
+        assertEquals("new_ix", reparsed.getName().getName());
+        assertTrue(reparsed.isConcurrently());
+        assertEquals(2, CCJSqlParserUtil.parseStatements(expected + "; SELECT 1").size());
+        drop.setConcurrently(false);
+        assertEquals(expected.replace("CONCURRENTLY ", ""), drop.toString());
+    }
+
+    @Test
+    void ordinaryAndQuotedConcurrentNamesArePreserved() throws JSQLParserException {
+        for (String sql : new String[] {"DROP TABLE concurrently", "DROP INDEX \"concurrently\"",
+                "DROP INDEX ix1, ix2 CASCADE", "DROP INDEX ix ON t ALGORITHM = INPLACE"}) {
+            Drop drop = (Drop) CCJSqlParserUtil.parse(sql);
+            assertFalse(drop.isConcurrently());
+            assertEquals(sql, drop.toString());
+        }
+    }
+}