From 438cdac5f2b9931153a9359acc92aade4fb57a8d Mon Sep 17 00:00:00 2001
From: Michael Simons <michael.simons@neo4j.com>
Date: Mon, 11 Mar 2024 10:17:32 +0100
Subject: [PATCH] refactor: Make sure result set can only be consumed once, add
 test for empty result set meta data

Closes #419.
---
 .../neo4j/jdbc/it/cp/PreparedStatementIT.java | 29 +++++++++++++++++++
 .../java/org/neo4j/jdbc/StatementImpl.java    |  8 +++++
 2 files changed, 37 insertions(+)

diff --git a/neo4j-jdbc-it/neo4j-jdbc-it-cp/src/test/java/org/neo4j/jdbc/it/cp/PreparedStatementIT.java b/neo4j-jdbc-it/neo4j-jdbc-it-cp/src/test/java/org/neo4j/jdbc/it/cp/PreparedStatementIT.java
index c33f4d1ab..299a884d3 100644
--- a/neo4j-jdbc-it/neo4j-jdbc-it-cp/src/test/java/org/neo4j/jdbc/it/cp/PreparedStatementIT.java
+++ b/neo4j-jdbc-it/neo4j-jdbc-it-cp/src/test/java/org/neo4j/jdbc/it/cp/PreparedStatementIT.java
@@ -34,6 +34,8 @@
 import java.sql.Statement;
 import java.sql.Time;
 import java.sql.Timestamp;
+import java.sql.Types;
+import java.time.Instant;
 import java.time.LocalDate;
 import java.time.LocalDateTime;
 import java.time.LocalTime;
@@ -233,6 +235,33 @@ void executeShouldAutomaticallyTranslate() throws SQLException {
 		}
 	}
 
+	// GH-419
+	@Test
+	void resultSetMustNotThrowWhenEmpty() throws SQLException {
+		try (var connection = getConnection();
+				var stmt = connection.prepareStatement("MATCH(p:Person) WHERE p.date >= ? AND p.date  < ? RETURN p")) {
+
+			var ts = Timestamp.from(Instant.now());
+			stmt.setTimestamp(1, ts);
+			stmt.setTimestamp(2, ts);
+			stmt.execute();
+			var resultSet = stmt.getResultSet();
+			var resultSetMetaData = resultSet.getMetaData();
+			int columnCount = resultSetMetaData.getColumnCount();
+			assertThat(columnCount).isOne();
+			for (int c = 1; c < columnCount + 1; c++) {
+				var label = resultSetMetaData.getColumnLabel(c);
+				assertThat(label).isEqualTo("p");
+				var type = resultSetMetaData.getColumnType(c);
+				assertThat(type).isEqualTo(Types.NULL);
+				var typeName = resultSetMetaData.getColumnTypeName(c);
+				assertThat(typeName).isEmpty();
+			}
+			resultSet.close();
+
+		}
+	}
+
 	@Nested
 	class SymmetricTypeConversionInPreparedStatementAndResultSet {
 
diff --git a/neo4j-jdbc/src/main/java/org/neo4j/jdbc/StatementImpl.java b/neo4j-jdbc/src/main/java/org/neo4j/jdbc/StatementImpl.java
index 79b3a71d3..d61aa4211 100644
--- a/neo4j-jdbc/src/main/java/org/neo4j/jdbc/StatementImpl.java
+++ b/neo4j-jdbc/src/main/java/org/neo4j/jdbc/StatementImpl.java
@@ -33,6 +33,7 @@
 import java.util.Map;
 import java.util.Objects;
 import java.util.Optional;
+import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.function.UnaryOperator;
 import java.util.logging.Level;
 import java.util.logging.Logger;
@@ -84,6 +85,8 @@ non-sealed class StatementImpl implements Neo4jStatement {
 
 	private final Warnings warnings;
 
+	private final AtomicBoolean resultSetAcquired = new AtomicBoolean(false);
+
 	StatementImpl(Connection connection, Neo4jTransactionSupplier transactionSupplier,
 			UnaryOperator<String> sqlProcessor, Warnings localWarnings) {
 		this.connection = Objects.requireNonNull(connection);
@@ -121,6 +124,7 @@ protected final ResultSet executeQuery0(String sql, boolean applyProcessor, Map<
 		var runAndPull = transaction.runAndPull(sql, getParameters(parameters), fetchSize, this.queryTimeout);
 		this.resultSet = new ResultSetImpl(this, transaction, runAndPull.runResponse(), runAndPull.pullResponse(),
 				this.fetchSize, this.maxRows, this.maxFieldSize);
+		this.resultSetAcquired.set(false);
 		return this.resultSet;
 	}
 
@@ -287,6 +291,9 @@ else if (entry.getValue() instanceof InputStream inputStream) {
 	@Override
 	public ResultSet getResultSet() throws SQLException {
 		assertIsOpen();
+		if (!this.resultSetAcquired.compareAndSet(false, true)) {
+			throw new SQLException("Result set has already been acquired");
+		}
 		return (this.multipleResultsApi && this.updateCount == -1) ? this.resultSet : null;
 	}
 
@@ -472,6 +479,7 @@ private void closeResultSet() throws SQLException {
 		if (this.resultSet != null) {
 			this.resultSet.close();
 			this.resultSet = null;
+			this.resultSetAcquired.set(false);
 		}
 	}