EXPLAIN is broken for some cases #6194
Description
To reproduce
Go to demo and try these three queries:
EXPLAIN CREATE TABLE trades AS
(
SELECT
rnd_symbol('a', 'b') symbol,
rnd_symbol('Buy', 'Sell') side,
rnd_double() price,
rnd_double() amount,
x::timestamp timestamp
FROM long_sequence(10)
) TIMESTAMP(timestamp) PARTITION BY DAY;
EXPLAIN INSERT INTO trades
SELECT
rnd_symbol('a', 'b') symbol,
rnd_symbol('Buy', 'Sell') side,
rnd_double() price,
rnd_double() amount,
x::timestamp timestamp
FROM long_sequence(10);
EXPLAIN UPDATE trades SET amount = 0 WHERE timestamp IN '2022-11-11';
The INSERT and UPDATE versions complain about permissions, but we are just explaining. We should be good.
Now, for a second issue. Run the same queries on your local instance with permissions. The last query breaks with this trace
2025-09-26T10:47:10.924606Z C i.q.c.h.p.JsonQueryProcessorState [1685774664889] internal error [ex=
java.lang.UnsupportedOperationException
at io.questdb.cairo.sql.RecordCursorFactory.getCursor(RecordCursorFactory.java:154)
at io.questdb.griffin.engine.table.FilteredRecordCursorFactory.getCursor(FilteredRecordCursorFactory.java:59)
at io.questdb.griffin.engine.table.VirtualRecordCursorFactory.getCursor(VirtualRecordCursorFactory.java:106)
at io.questdb.griffin.SqlCodeGenerator$RecordCursorFactoryStub.getCursor(SqlCodeGenerator.java:6807)
at io.questdb.griffin.engine.ExplainPlanFactory$ExplainPlanRecordCursor.of(ExplainPlanFactory.java:141)
at io.questdb.griffin.engine.ExplainPlanFactory.getCursor(ExplainPlanFactory.java:60)
at io.questdb.cutlass.http.processors.JsonQueryProcessor.executeSelect0(JsonQueryProcessor.java:686)
at io.questdb.cutlass.http.processors.JsonQueryProcessor.executeExplain(JsonQueryProcessor.java:627)
at io.questdb.cutlass.http.processors.JsonQueryProcessor.compileAndExecuteQuery(JsonQueryProcessor.java:513)
at io.questdb.cutlass.http.processors.JsonQueryProcessor.execute0(JsonQueryProcessor.java:215)
at io.questdb.cutlass.http.processors.JsonQueryProcessor.onRequestComplete(JsonQueryProcessor.java:292)
at io.questdb.cutlass.http.HttpConnectionContext.handleClientRecv(HttpConnectionContext.java:910)
at io.questdb.cutlass.http.HttpConnectionContext.handleClientOperation(HttpConnectionContext.java:307)
at io.questdb.cutlass.http.HttpServer.handleClientOperation(HttpServer.java:343)
at io.questdb.cutlass.http.HttpServer$1.lambda$$0(HttpServer.java:129)
at io.questdb.network.AbstractIODispatcher.processIOQueue(AbstractIODispatcher.java:217)
at io.questdb.cutlass.http.HttpServer$1.run(HttpServer.java:133)
at io.questdb.mp.Worker.run(Worker.java:152)
I checked and this has been broken for a while. Back in QuestDB 7.0.0 it was working. As of QuestDB 8.0.1 it breaks. So it happened somewhere in between.
QuestDB version:
8.0.0 and higher
OS, in case of Docker specify Docker and the Host OS:
ubuntu and mac
File System, in case of Docker specify Host File System:
ext4
Full Name:
javier
Affiliation:
questdb
Have you followed Linux, MacOs kernel configuration steps to increase Maximum open files and Maximum virtual memory areas limit?
- Yes, I have
Additional context
No response