Allow to insert default instead of Null in insert-select / insert-select-union-all#23524
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KochetovNicolai merged 12 commits intoClickHouse:masterfrom Apr 26, 2021
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As the feature is unrelated to formats, it will be better to make a separate setting. |
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| auto nullable_column = ColumnNullable::create(query_columns[col_idx], ColumnUInt8::create(query_columns[col_idx]->size(), 0)); | ||
| ColumnWithTypeAndName new_column(std::move(nullable_column), std::make_shared<DataTypeNullable>(column.type), column.name); |
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Note: there are functions ColumnPtr makeNullable(const ColumnPtr & column); (in ColumnNullable.h) and DataTypePtr makeNullable(const DataTypePtr & type); (in DataTypeNullable.h)
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Also, could please add comment why do we need to change query_sample_block here?
And why it is safe (because AddingDefaultBlockOutputStream will remove nullable)
| addDefaultRequiredExpressionsRecursively(block, required_column_name, columns, default_expr_list_accum, added_columns); | ||
| if (is_column_in_query && convert_null_to_default) | ||
| { | ||
| auto null_as_default_expr = makeASTFunction("ifNull", std::make_shared<ASTIdentifier>(required_column_name), column_default_expr); |
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I think that we also need to add CAST here for column_default_expr. Similar as in else part
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Suspicious. |
| SELECT * FROM test_null_as_default ORDER BY s; | ||
| SELECT ''; | ||
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| REPLACE TABLE test_null_as_default (s String DEFAULT 'WORLD', ss String DEFAULT 'PEOPLE') ENGINE = Memory; |
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Also it is good to add cases:
- with different types, like
x UInt64, y UInt8 default x - 10 - with recursive defaults, like
x UInt32, y UInt32 default z + 1, z UInt32 default x + 1(and insert into (x, y))
KochetovNicolai
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Apr 23, 2021
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Looks fine in general.
KochetovNicolai
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Apr 23, 2021
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There is still a bug: should be easy to reproduce |
kssenii
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Functional stateful tests - |
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Internal documentation ticket: DOCSUP-8939. |
azat
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Oct 14, 2021
…able column
Required columns of the default expression should not be converted to NULL,
since this map value to default and MATERIALIZED values will not work.
Consider the following structure:
- A Nullable(Int64)
- X Int64 materialized coalesce(A, -1)
With recursive_null_as_default=true you will get:
_CAST(coalesce(A, -1), 'Int64') AS X, NULL AS A
And this will ignore default expression.
Fixes: ClickHouse#23524 (Cc: @kssenii)
Fixes: ClickHouse#29729 (Cc: @tavplubix)
Backport: 21.7+
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Changelog entry (a user-readable short description of the changes that goes to CHANGELOG.md):
If
insert_null_as_default= 1, insert default values instead of NULL inINSERT ... SELECTandINSERT ... SELECT ... UNION ALL ...queries. Closes #22832.