feat: parse PostgreSQL DECLARE CURSOR, FETCH, MOVE and CLOSE

PostgreSQL cursor statements failed to parse: DECLARE took only the
SQL Server DECLARE @variable, and FETCH, MOVE and CLOSE started no
statement, so scripts that page through a query with a cursor failed.

Add the statement.cursor package. DeclareCursorStatement keeps the
cursor options in their order (CursorOption), the holdability and the
query. FetchCursorStatement covers FETCH and MOVE with an optional
FetchDirection keyword, a signed 32-bit count or ALL, and FROM or IN.
CloseCursorStatement covers CLOSE name and CLOSE ALL. As in
PostgreSQL's grammar, a direction word that ends the statement names
the cursor, and reserved words name none.

Dialect.POSTGRESQL reads these statements. Without a dialect they parse
when they take the PostgreSQL form, so other products' FETCH ... INTO
stays an unsupported statement. Other dialects and DECLARE @variable
are unchanged. MOVE becomes a non-reserved keyword. Wire the statements
into the deparser, visitors, table finder, validation (declareCursor,
fetchCursor, closeCursor) and feature analysis.

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

Author: minleejae

README.md

@@ -152,6 +152,7 @@ and missing syntax gets added on demand — [open an issue](https://github.com/J
 | **PostgreSQL maintenance** | `VACUUM` · `ANALYZE` · `CLUSTER` · `CHECKPOINT` |
 | **MySQL locks** | `LOCK TABLES` · `UNLOCK TABLES` · `LOCK INSTANCE FOR BACKUP` · `UNLOCK INSTANCE` |
 | **PostgreSQL session statements** | `DISCARD` · `LISTEN` · `UNLISTEN` · `SHOW`/`RESET TIME ZONE`/`TRANSACTION ISOLATION LEVEL`/`SESSION AUTHORIZATION` · `COPY` options from before 9.0 |
+| **PostgreSQL cursors** | `DECLARE … CURSOR` · `FETCH` · `MOVE` · `CLOSE` |
 | **MySQL account management** | `CREATE`/`ALTER`/`RENAME USER` · `CREATE ROLE` · `SET ROLE` · `SET DEFAULT ROLE` · `SET PASSWORD` |
 | **Tablespaces** | MySQL and PostgreSQL `CREATE TABLESPACE` · `ALTER TABLESPACE` |
 | **PostgreSQL RLS** | `CREATE POLICY` · `ALTER TABLE … ENABLE`/`DISABLE`/`FORCE`/`NO FORCE ROW LEVEL SECURITY` |

src/main/java/net/sf/jsqlparser/parser/feature/Feature.java

@@ -51,6 +51,9 @@
 import net.sf.jsqlparser.statement.create.trigger.CreateEventTrigger;
 import net.sf.jsqlparser.statement.create.view.AlterView;
 import net.sf.jsqlparser.statement.create.view.CreateView;
+import net.sf.jsqlparser.statement.cursor.CloseCursorStatement;
+import net.sf.jsqlparser.statement.cursor.DeclareCursorStatement;
+import net.sf.jsqlparser.statement.cursor.FetchCursorStatement;
 import net.sf.jsqlparser.statement.delete.Delete;
 import net.sf.jsqlparser.statement.drop.Drop;
 import net.sf.jsqlparser.statement.execute.Execute;
@@ -955,6 +958,24 @@ public enum Feature {
      * @see DeclareStatement
      */
     declare,
+    /**
+     * PostgreSQL "DECLARE name CURSOR FOR query" statement is allowed
+     *
+     * @see DeclareCursorStatement
+     */
+    declareCursor,
+    /**
+     * PostgreSQL "FETCH" and "MOVE" statements of a cursor are allowed
+     *
+     * @see FetchCursorStatement
+     */
+    fetchCursor,
+    /**
+     * PostgreSQL "CLOSE" statement of a cursor is allowed
+     *
+     * @see CloseCursorStatement
+     */
+    closeCursor,
 
     /** SQL Server local table variables in queries and DML targets. */
     tableVariable,

src/main/java/net/sf/jsqlparser/statement/StatementFeatureVisitor.java

@@ -84,6 +84,9 @@
 import net.sf.jsqlparser.statement.create.usermapping.CreateUserMapping;
 import net.sf.jsqlparser.statement.create.view.AlterView;
 import net.sf.jsqlparser.statement.create.view.CreateView;
+import net.sf.jsqlparser.statement.cursor.CloseCursorStatement;
+import net.sf.jsqlparser.statement.cursor.DeclareCursorStatement;
+import net.sf.jsqlparser.statement.cursor.FetchCursorStatement;
 import net.sf.jsqlparser.statement.delete.Delete;
 import net.sf.jsqlparser.statement.drop.Drop;
 import net.sf.jsqlparser.statement.drop.DropPolicy;
@@ -1019,6 +1022,33 @@ public <S> Void visit(DiscardStatement discard, S context) {
         return null;
     }
 
+    @Override
+    public <S> Void visit(DeclareCursorStatement declareCursor, S context) {
+        // opens a cursor of the session over its query, which reads as the cursor is fetched
+        analysis.claimTopLevel();
+        analysis.certain(StmtFeature.MODIFIES_SESSION);
+        if (declareCursor.getQuery() != null) {
+            declareCursor.getQuery().accept(analysis.selects, context);
+        }
+        return null;
+    }
+
+    @Override
+    public <S> Void visit(FetchCursorStatement fetchCursor, S context) {
+        // moves the cursor and runs its query that far; only FETCH returns the rows
+        if (analysis.claimTopLevel() && fetchCursor.getKind() == FetchCursorStatement.Kind.FETCH) {
+            analysis.certain(StmtFeature.RETURNS_RESULT_SET);
+        }
+        analysis.certain(StmtFeature.MODIFIES_SESSION);
+        analysis.possible(StmtFeature.READS_DATA);
+        return null;
+    }
+
+    @Override
+    public <S> Void visit(CloseCursorStatement closeCursor, S context) {
+        return sessionOnly();
+    }
+
     @Override
     public <S> Void visit(AlterSystemStatement alterSystemStatement, S context) {
         analysis.claimTopLevel();

src/main/java/net/sf/jsqlparser/statement/StatementVisitor.java

@@ -112,6 +112,9 @@
 import net.sf.jsqlparser.statement.upsert.Upsert;
 import net.sf.jsqlparser.statement.create.macro.CreateMacro;
 import net.sf.jsqlparser.statement.create.extension.CreateExtensionRepository;
+import net.sf.jsqlparser.statement.cursor.CloseCursorStatement;
+import net.sf.jsqlparser.statement.cursor.DeclareCursorStatement;
+import net.sf.jsqlparser.statement.cursor.FetchCursorStatement;
 import net.sf.jsqlparser.statement.export.ExportDataStatement;
 import net.sf.jsqlparser.statement.load.LoadDataStatement;
 
@@ -753,6 +756,30 @@ default void visit(BackupLockStatement backupLock) {
         visit(backupLock, null);
     }
 
+    default <S> T visit(DeclareCursorStatement declareCursor, S context) {
+        return null;
+    }
+
+    default void visit(DeclareCursorStatement declareCursor) {
+        visit(declareCursor, null);
+    }
+
+    default <S> T visit(FetchCursorStatement fetchCursor, S context) {
+        return null;
+    }
+
+    default void visit(FetchCursorStatement fetchCursor) {
+        visit(fetchCursor, null);
+    }
+
+    default <S> T visit(CloseCursorStatement closeCursor, S context) {
+        return null;
+    }
+
+    default void visit(CloseCursorStatement closeCursor) {
+        visit(closeCursor, null);
+    }
+
     <S> T visit(CreatePolicy createPolicy, S context);
 
     default void visit(CreatePolicy createPolicy) {

src/main/java/net/sf/jsqlparser/statement/StatementVisitorAdapter.java

@@ -130,6 +130,9 @@
 import net.sf.jsqlparser.util.TableDefinitionTraversal;
 import net.sf.jsqlparser.statement.create.macro.CreateMacro;
 import net.sf.jsqlparser.statement.create.extension.CreateExtensionRepository;
+import net.sf.jsqlparser.statement.cursor.CloseCursorStatement;
+import net.sf.jsqlparser.statement.cursor.DeclareCursorStatement;
+import net.sf.jsqlparser.statement.cursor.FetchCursorStatement;
 import net.sf.jsqlparser.statement.export.ExportDataStatement;
 import net.sf.jsqlparser.statement.load.LoadDataStatement;
 
@@ -587,6 +590,24 @@ public <S> T visit(BackupLockStatement backupLock, S context) {
         return null;
     }
 
+    @Override
+    public <S> T visit(DeclareCursorStatement declareCursor, S context) {
+        if (declareCursor.getQuery() != null) {
+            declareCursor.getQuery().accept(selectVisitor, context);
+        }
+        return null;
+    }
+
+    @Override
+    public <S> T visit(FetchCursorStatement fetchCursor, S context) {
+        return null;
+    }
+
+    @Override
+    public <S> T visit(CloseCursorStatement closeCursor, S context) {
+        return null;
+    }
+
     @Override
     public <S> T visit(CreatePolicy createPolicy, S context) {
         fromItemVisitor.visitFromItem(createPolicy.getTable(), context);

src/main/java/net/sf/jsqlparser/statement/cursor/CloseCursorStatement.java

@@ -0,0 +1,64 @@
+/*-
+ * #%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.cursor;
+
+import net.sf.jsqlparser.parser.ASTNodeAccessImpl;
+import net.sf.jsqlparser.statement.Statement;
+import net.sf.jsqlparser.statement.StatementVisitor;
+
+/**
+ * PostgreSQL {@code CLOSE {name | ALL}}, which closes one cursor or every open cursor of the
+ * session.<br>
+ * Examples:<br>
+ * CLOSE c<br>
+ * CLOSE ALL<br>
+ *
+ * @see <a href="https://www.postgresql.org/docs/18/sql-close.html">PostgreSQL CLOSE</a>
+ */
+public class CloseCursorStatement extends ASTNodeAccessImpl implements Statement {
+    private String cursorName;
+
+    /** CLOSE ALL. */
+    public CloseCursorStatement() {}
+
+    public CloseCursorStatement(String cursorName) {
+        this.cursorName = cursorName;
+    }
+
+    /** Returns null for CLOSE ALL. */
+    public String getCursorName() {
+        return cursorName;
+    }
+
+    /** A null name makes the statement CLOSE ALL. */
+    public void setCursorName(String cursorName) {
+        this.cursorName = cursorName;
+    }
+
+    /** Whether the statement is CLOSE ALL, which is when it has no cursor name. */
+    public boolean isAll() {
+        return cursorName == null;
+    }
+
+    @Override
+    public StringBuilder appendTo(StringBuilder builder) {
+        return builder.append("CLOSE ").append(isAll() ? "ALL" : cursorName);
+    }
+
+    @Override
+    public String toString() {
+        return appendTo(new StringBuilder()).toString();
+    }
+
+    @Override
+    public <T, S> T accept(StatementVisitor<T> statementVisitor, S context) {
+        return statementVisitor.visit(this, context);
+    }
+}

src/main/java/net/sf/jsqlparser/statement/cursor/CursorOption.java

@@ -0,0 +1,44 @@
+/*-
+ * #%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.cursor;
+
+/**
+ * An option of PostgreSQL's {@code DECLARE name [options] CURSOR}. PostgreSQL's grammar takes them
+ * in any order and repeated; the server rejects contradicting ones such as SCROLL and NO SCROLL
+ * when it runs the statement.
+ *
+ * @see <a href="https://www.postgresql.org/docs/18/sql-declare.html">PostgreSQL DECLARE</a>
+ */
+public enum CursorOption {
+    /** Returns the rows in binary rather than text format. */
+    BINARY("BINARY"),
+
+    /** Leaves the visibility of later changes to the implementation. */
+    ASENSITIVE("ASENSITIVE"),
+
+    /** Hides later changes; PostgreSQL's cursors are always insensitive. */
+    INSENSITIVE("INSENSITIVE"),
+
+    /** Allows fetching backward. */
+    SCROLL("SCROLL"),
+
+    /** Forbids fetching backward. */
+    NO_SCROLL("NO SCROLL");
+
+    private final String keyword;
+
+    CursorOption(String keyword) {
+        this.keyword = keyword;
+    }
+
+    public String getKeyword() {
+        return keyword;
+    }
+}