Read using IcebergLocal returns Nulls instead of actual rows

[alsugiliazova]

Describe the bug
Introduced in docker://altinity/clickhouse-server:25.8.9.20207.altinityantalya-alpine and has been like that in all new versions.

SELECT *
FROM icebergLocal('/var/lib/clickhouse/user_files/iceberg_local_basic', 'Parquet', SETTINGS iceberg_metadata_table_uuid = 'fbb0a4ea-488e-4387-9cdc-23888ec32fae')
FORMAT TSV

Query id: 53c9aef3-fa0b-43e5-b386-eeb9f8c316a6

\N	\N	\N
\N	\N	\N
\N	\N	\N

3 rows in set. Elapsed: 0.004 sec. 

DESCRIBE TABLE icebergLocal('/var/lib/clickhouse/user_files/iceberg_local_basic', 'Parquet', SETTINGS iceberg_metadata_table_uuid = 'fbb0a4ea-488e-4387-9cdc-23888ec32fae')

Query id: 088a7662-7801-44e3-8b1c-13b818762105

   ┌─name────┬─type──────────────┬─default_type─┬─default_expression─┬─comment─┬─codec_expression─┬─ttl_expression─┐
1. │ name    │ Nullable(String)  │              │                    │         │                  │                │
2. │ double  │ Nullable(Float64) │              │                    │         │                  │                │
3. │ integer │ Nullable(Int64)   │              │                    │         │                  │                │
   └─────────┴───────────────────┴──────────────┴────────────────────┴─────────┴──────────────────┴────────────────┘

3 rows in set. Elapsed: 0.001 sec. 

Expected result

SELECT version()

Query id: d2049702-453b-49fd-b210-26a16e02905c

   ┌─version()────────────────────┐
1. │ 25.6.5.20420.altinityantalya │
   └──────────────────────────────┘

1 row in set. Elapsed: 0.001 sec. 

clickhouse1 :) SELECT *
                                      FROM icebergLocal(
                                          '/var/lib/clickhouse/user_files/iceberg_local_basic',
                                          'Parquet',
                                          SETTINGS iceberg_metadata_table_uuid = 'fbb0a4ea-488e-4387-9cdc-23888ec32fae'
                                      )
                                      ORDER BY name
                                      FORMAT TSV

SELECT *
FROM icebergLocal('/var/lib/clickhouse/user_files/iceberg_local_basic', 'Parquet', SETTINGS iceberg_metadata_table_uuid = 'fbb0a4ea-488e-4387-9cdc-23888ec32fae')
ORDER BY name ASC
FORMAT TSV

Query id: f05099d2-f358-4718-a389-44f866c7a05d

Alice	195.23	20
Bob	123.45	30
Charlie	67.89	40

3 rows in set. Elapsed: 0.006 sec. 

clickhouse1 :) 

Root cause is PR #1069

When allow_experimental_iceberg_read_optimization is turned off, I can see rows again.

SET allow_experimental_iceberg_read_optimization = 0

Query id: 8e051545-d639-4097-8005-606c0ed2875b

Ok.

0 rows in set. Elapsed: 0.001 sec. 

SELECT *
FROM icebergLocal('/var/lib/clickhouse/user_files/iceberg_local_basic', 'Parquet', SETTINGS iceberg_metadata_table_uuid = 'fbb0a4ea-488e-4387-9cdc-23888ec32fae')
ORDER BY name ASC
FORMAT TSV

Query id: ab4c2f6b-7051-4b32-bec0-065828fd8128

Alice	195.23	20
Bob	123.45	30
Charlie	67.89	40

3 rows in set. Elapsed: 0.010 sec.