From 29fe7317286062ed250912172a984abbc1bf081d Mon Sep 17 00:00:00 2001
From: ispyisail <shane.ringrose@gmail.com>
Date: Sun, 27 Sep 2026 14:00:07 +1300
Subject: [PATCH] Fix read-only queries stopping after the first row

Since #1046, QETSql::execReadOnly() runs a query with PRAGMA query_only
set and switches it off before returning. Switching it off aborts a
statement SQLite is still stepping through ("abort due to ROLLBACK"), and
QSQLITE has already stepped to the first row by then. A query that
produces its rows as it goes -- a UNION ALL without ORDER BY -- therefore
came back with its first row only and no error. A sorted query was not
affected, because SQLite has read every row before returning the first.

Every query from the SQL box of a table, a saved <graphics_table> query
and the scripting qet.query() goes through here.

The checked run is now finished before query_only is switched off, and a
query that passed is run again for the caller. SQLite refuses a write at
its first step, so passing that step is what proves a statement reads
only; the second run is of a statement already shown to be read-only.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01G2d2Zi8BfrYRPX88zhaoFG
---
 sources/dataBase/sqlreadonly.cpp |  7 +++++++
 tests/qttest/tst_sqlreadonly.cpp | 17 +++++++++++++++++
 2 files changed, 24 insertions(+)

diff --git a/sources/dataBase/sqlreadonly.cpp b/sources/dataBase/sqlreadonly.cpp
index 95996bde5..f61aabbea 100644
--- a/sources/dataBase/sqlreadonly.cpp
+++ b/sources/dataBase/sqlreadonly.cpp
@@ -86,9 +86,16 @@ QSqlQuery execReadOnly(const QSqlDatabase &db, const QString &query, QString *er
 
 	QSqlQuery result(db);
 	const bool ok = result.exec(query);
+		//Switching query_only off aborts a statement SQLite is still
+		//stepping through -- an unsorted UNION ALL then ends after its
+		//first row. So the checked run is finished first, and a statement
+		//that passed is run again for the caller: SQLite refuses a write
+		//at its first step, so passing that step proves it read-only.
+	result.finish();
 	QSqlQuery(db).exec(QStringLiteral("PRAGMA query_only = OFF"));
 
 	if (ok) {
+		result.exec(query);
 		return result;
 	}
 
diff --git a/tests/qttest/tst_sqlreadonly.cpp b/tests/qttest/tst_sqlreadonly.cpp
index a96735fd9..7159e1c28 100644
--- a/tests/qttest/tst_sqlreadonly.cpp
+++ b/tests/qttest/tst_sqlreadonly.cpp
@@ -40,6 +40,7 @@
 
 #include <QtTest>
 #include <QSqlDatabase>
+#include <QSqlError>
 #include <QSqlQuery>
 
 class TstSqlReadOnly : public QObject
@@ -63,6 +64,7 @@ class TstSqlReadOnly : public QObject
 		void doesNotExecuteWhatItRefuses();
 		void refusedQueryCannotBeRunAgain();
 		void acceptedQueryRunAgainStillReads();
+		void returnsEveryRowOfACompoundSelect();
 		void leavesTheConnectionWritable();
 
 	private:
@@ -242,6 +244,21 @@ void TstSqlReadOnly::acceptedQueryRunAgainStillReads()
 	QCOMPARE(n, 2);
 }
 
+void TstSqlReadOnly::returnsEveryRowOfACompoundSelect()
+{
+	// Switching query_only off aborts a statement SQLite is still
+	// stepping through, and an unsorted UNION ALL is one: it came back
+	// with its first row only.
+	QSqlQuery q = QETSql::execReadOnly(
+				m_db, "SELECT uuid FROM element UNION ALL SELECT uuid FROM element");
+	QStringList uuids;
+	while (q.next()) {
+		uuids << q.value(0).toString();
+	}
+	QVERIFY(!q.lastError().isValid());
+	QCOMPARE(uuids, QStringList({"a", "b", "a", "b"}));
+}
+
 void TstSqlReadOnly::leavesTheConnectionWritable()
 {
 	// query_only must not outlive the call, whatever its outcome: the