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[BUG] Table with nested failing to load #399

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dermasmid opened this issue Jun 3, 2024 · 2 comments · Fixed by #404
Closed

[BUG] Table with nested failing to load #399

dermasmid opened this issue Jun 3, 2024 · 2 comments · Fixed by #404
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@dermasmid
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Describe the bug

im seeing DESCRIBE TABLE is never supposed to return Nested type. It should always yield its Array fields directly.

heres a example table:

chi-sonic-cluster-main-0-2-0.chi-sonic-cluster-main-0-2.clickhouse.svc.cluster.local :) create table default.nested_test (s String, n Nested(x Nullable(String), y String)) engine=MergeTree order by s
CREATE TABLE default.nested_test
(
    `s` String,
    `n` Nested(x Nullable(String), y String)
)
ENGINE = MergeTree
ORDER BY s
Query id: 4966dc7b-a268-44ad-9a03-2b820bc8c579
Ok.
0 rows in set. Elapsed: 0.009 sec. 
chi-sonic-cluster-main-0-2-0.chi-sonic-cluster-main-0-2.clickhouse.svc.cluster.local :) describe table default.nested_test
DESCRIBE TABLE default.nested_test
Query id: b7454634-ae12-4c29-bcb1-0938a49398db
   ┌─name─┬─type─────────────────────────────────┬─default_type─┬─default_expression─┬─comment─┬─codec_expression─┬─ttl_expression─┐
1. │ s    │ String                               │              │                    │         │                  │                │
2. │ n    │ Nested(x Nullable(String), y String) │              │                    │         │                  │                │
   └──────┴──────────────────────────────────────┴──────────────┴────────────────────┴─────────┴──────────────────┴────────────────┘
2 rows in set. Elapsed: 0.001 sec. 
chi-sonic-cluster-main-0-2-0.chi-sonic-cluster-main-0-2.clickhouse.svc.cluster.local :) describe table default.nested_test SETTINGS describe_include_subcolumns=1
DESCRIBE TABLE default.nested_test
SETTINGS describe_include_subcolumns = 1
Query id: 0ad77427-0548-4212-92f1-4bffdd2b7890
   ┌─name─────┬─type─────────────────────────────────┬─default_type─┬─default_expression─┬─comment─┬─codec_expression─┬─ttl_expression─┬─is_subcolumn─┐
1. │ s        │ String                               │              │                    │         │                  │                │            0 │
2. │ n        │ Nested(x Nullable(String), y String) │              │                    │         │                  │                │            0 │
3. │ n.size0  │ UInt64                               │              │                    │         │                  │                │            1 │
4. │ n.x      │ Array(Nullable(String))              │              │                    │         │                  │                │            1 │
5. │ n.x.null │ Array(UInt8)                         │              │                    │         │                  │                │            1 │
6. │ n.y      │ Array(String)                        │              │                    │         │                  │                │            1 │
   └──────────┴──────────────────────────────────────┴──────────────┴────────────────────┴─────────┴──────────────────┴────────────────┴──────────────┘
6 rows in set. Elapsed: 0.001 sec.

as you can see, the nested fields are being returned as well

Steps to reproduce

Expected behaviour

Error log

Configuration

Environment

  • Kafka-Connect version:
  • Kafka Connect configuration:
  • Kafka version:
  • Kafka environment:
  • OS:

ClickHouse server

  • ClickHouse Server version: 24.5
  • ClickHouse Server non-default settings, if any:
  • CREATE TABLE statements for tables involved:
  • Sample data for all these tables, use clickhouse-obfuscator if necessary
@dermasmid dermasmid added the bug Something isn't working label Jun 3, 2024
@dermasmid dermasmid mentioned this issue Jun 3, 2024
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@dermasmid
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turns out its because we have flatten_nested=0
heres a comparison

chi-sonic-cluster-main-0-2-0.chi-sonic-cluster-main-0-2.clickhouse.svc.cluster.local :) describe table default.nested_test_1 SETTINGS describe_include_subcolumns=1
DESCRIBE TABLE default.nested_test_1
SETTINGS describe_include_subcolumns = 1
Query id: b42e99d7-20c6-4546-b13f-6607b044a3e5
   ┌─name──────┬─type────────────────────┬─default_type─┬─default_expression─┬─comment─┬─codec_expression─┬─ttl_expression─┬─is_subcolumn─┐
1. │ s         │ String                  │              │                    │         │                  │                │            0 │
2. │ n.x       │ Array(Nullable(String)) │              │                    │         │                  │                │            0 │
3. │ n.y       │ Array(String)           │              │                    │         │                  │                │            0 │
4. │ n.x.size0 │ UInt64                  │              │                    │         │                  │                │            1 │
5. │ n.x.null  │ Array(UInt8)            │              │                    │         │                  │                │            1 │
6. │ n.y.size0 │ UInt64                  │              │                    │         │                  │                │            1 │
   └───────────┴─────────────────────────┴──────────────┴────────────────────┴─────────┴──────────────────┴────────────────┴──────────────┘
6 rows in set. Elapsed: 0.001 sec. 
chi-sonic-cluster-main-0-2-0.chi-sonic-cluster-main-0-2.clickhouse.svc.cluster.local :) describe table default.nested_test SETTINGS describe_include_subcolumns=1
DESCRIBE TABLE default.nested_test
SETTINGS describe_include_subcolumns = 1
Query id: 91063e89-cb93-402d-bab5-2b77ecb06adc
   ┌─name─────┬─type─────────────────────────────────┬─default_type─┬─default_expression─┬─comment─┬─codec_expression─┬─ttl_expression─┬─is_subcolumn─┐
1. │ s        │ String                               │              │                    │         │                  │                │            0 │
2. │ n        │ Nested(x Nullable(String), y String) │              │                    │         │                  │                │            0 │
3. │ n.size0  │ UInt64                               │              │                    │         │                  │                │            1 │
4. │ n.x      │ Array(Nullable(String))              │              │                    │         │                  │                │            1 │
5. │ n.x.null │ Array(UInt8)                         │              │                    │         │                  │                │            1 │
6. │ n.y      │ Array(String)                        │              │                    │         │                  │                │            1 │
   └──────────┴──────────────────────────────────────┴──────────────┴────────────────────┴─────────┴──────────────────┴────────────────┴──────────────┘
6 rows in set. Elapsed: 0.001 sec.

@Paultagoras
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Hmm, that's fascinating - I'll try playing around with flatten_nested a bit but we may just need to "warn" instead of error

@den-crane den-crane mentioned this issue Jun 4, 2024
Closed
@Paultagoras Paultagoras mentioned this issue Jun 5, 2024
Merged
@Paultagoras Paultagoras linked a pull request Jun 5, 2024 that will close this issue
Tweak to return null instead of throw exception #404
Merged
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Tweak to return null instead of throw exception ClickHouse/clickhouse-kafka-connect
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@Paultagoras @dermasmid