I found the reason. The subquery was not cached, even so it is not marked
as lazy. I attached the patch which solves this particular problem.
On Wednesday, April 11, 2018 at 6:36:42 PM UTC-4, Pavel wrote:
>
> The example below runs less than a second. If I change connection parameter
> to LAZY_QUERY_EXECUTION=1 then it takes forever.
>
>
> I tested with both 1.4.196 and 1.4.197. The same result.
>
>
> @Test
> public void subquery() throws Exception {
> Class.forName("org.h2.Driver");
> try (Connection conn =
> DriverManager.getConnection("jdbc:h2:mem:;LAZY_QUERY_EXECUTION=0")) {
> try (Statement stat = conn.createStatement()) {
> final int ROWS = 100000;
> stat.execute("CREATE TABLE ONE(X INTEGER , Y INTEGER )");
> try (PreparedStatement prep = conn.prepareStatement("insert into
> one values(?,?)")) {
> for (int row = 0; row < ROWS; row++) {
> prep.setInt(1, row / 100);
> prep.setInt(2, row);
> prep.execute();
> }
> }
> String s1 = "SELECT COUNT (*) from one where x in ( select y from
> one where y < 100)";
> try (ResultSet rs = stat.executeQuery(s1)) {
> rs.next();
> Assert.assertEquals(rs.getInt(1), 10000);
> }
> }
> }
> }
>
>
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Index: h2/src/main/org/h2/command/dml/Query.java
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- h2/src/main/org/h2/command/dml/Query.java (revision 8311:7310cac7dbeb4abef922b9b5c8f35a0b98f1f9ff)
+++ h2/src/main/org/h2/command/dml/Query.java (revision 8311+:7310cac7dbeb+)
@@ -68,6 +68,8 @@
private boolean cacheableChecked;
private boolean neverLazy;
+ protected boolean lazy;
+
Query(Session session) {
super(session);
}
@@ -348,7 +350,7 @@
}
fireBeforeSelectTriggers();
if (noCache || !session.getDatabase().getOptimizeReuseResults() ||
- session.isLazyQueryExecution()) {
+ lazy) {
return queryWithoutCacheLazyCheck(limit, target);
}
Value[] params = getParameterValues();
Index: h2/src/main/org/h2/command/dml/Select.java
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- h2/src/main/org/h2/command/dml/Select.java (revision 8311:7310cac7dbeb4abef922b9b5c8f35a0b98f1f9ff)
+++ h2/src/main/org/h2/command/dml/Select.java (revision 8311+:7310cac7dbeb+)
@@ -569,7 +569,7 @@
limitRows = Math.min(l, limitRows);
}
}
- boolean lazy = session.isLazyQueryExecution() &&
+ lazy = session.isLazyQueryExecution() &&
target == null && !isForUpdate && !isQuickAggregateQuery &&
limitRows != 0 && offsetExpr == null && isReadOnly();
int columnCount = expressions.size();
