Handle Iceberg data file missing null count stats

[alexjo2144]

Description

Null counts is an optional field and may be null. Handle that case appropriately by invalidating stats rather than throwing a NPE.

Is this change a fix, improvement, new feature, refactoring, or other?

Fix

Is this a change to the core query engine, a connector, client library, or the SPI interfaces? (be specific)

Iceberg connector

How would you describe this change to a non-technical end user or system administrator?

Related issues, pull requests, and links

Documentation

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( ) Sufficient documentation is included in this PR.
( ) Documentation PR is available with #prnumber.
( ) Documentation issue #issuenumber is filed, and can be handled later.

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# Iceberg
* Fix NPE when an Iceberg data file is missing null count statistics

[findinpath]

Please add a test to showcase this issue

[findinpath]

Here is a naive test case showcasing the bug you fixed

    @Test
    public void testNoMetrics()
    {
        assertUpdate("create table table_no_metrics_partitioned (name varchar, country varchar) WITH (partitioning = ARRAY['country'])");
        Table table = IcebergUtil.loadIcebergTable(trinoCatalog, tableOperationsProvider, TestingConnectorSession.SESSION,
                new SchemaTableName("tpch", "table_no_metrics_partitioned"));
        // skip metrics
        table.updateProperties()
                .set("write.metadata.metrics.default", "none")
                .commit();
        assertUpdate("INSERT INTO table_no_metrics_partitioned VALUES ('Christoph', 'AT'), (NULL, 'RO')", 2);
        assertEquals(computeActual("SELECT count(*) FROM \"table_no_metrics_partitioned$partitions\" WHERE data IS NOT NULL").getOnlyValue(), 0L);
    }

[findepi]

nice, this probably would exercise missing min/max as well, right? IIRC we didn't add a test then

[alexjo2144]

I tried this out, but I'm getting an empty Map for min/max/null-counts instead of null. I'd have to look at the Iceberg code, but maybe it changed at some point?

[alexjo2144]

We may also want to file an Issue to respect write.metadata.metrics.default and the other stats tuning properties at some point

[findinpath]

I did run the test on your branch @alexjo2144 and I inspected specifically to see whether the nullCounts map is NULL.

BTW I did the test on TestIcebergMergeAppend - it wouldn't fit for this PR, but I had there the trinoCatalog and tableOperationsProvider at hand.
I'm thinking that this is a good reason to handle #11828 in the near future to be covered against regressions that we can't catch when creating content with the latest version of Iceberg.

[findepi]

@alexjo2144 there are test failures

[findepi]

@alexjo2144 do you want RN for this?

[mosabua]

RN entry is in description .. I will use that

[findepi]

RN entry is in description .. I will use that

@mosabua thanks, missed that

* Fix NPE when an Iceberg data file is missing null count statistics

@alexjo2144 this should spell out NPE and should specify what operation could fail (SELECT? INSERT? SELECT from a system table?)