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https://issues.apache.org/jira/browse/ARROW-8065?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Francois Saint-Jacques updated ARROW-8065:
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Description:
Currently: a fragment is a product of a scan; it is a lazy collection of scan
tasks corresponding to a data source which is logically singular (like a single
file, a single row group, ...). It would be more useful if instead a fragment
were the direct object of a scan; one scans a fragment (or a collection of
fragments):
# Remove {{ScanOptions}} from Fragment's properties and move it into
{{Fragment::Scan}} parameters.
# Remove {{ScanOptions}} from {{Dataset::GetFragments}}. We can provide an
overload to support predicate pushdown in FileSystemDataset and UnionDataset
{{Dataset::GetFragments(std::shared_ptr<Expression> predicate)}}.
# Expose lazy accessor to Fragment::physical_schema()
# Consolidate ScanOptions and ScanContext
This will lessen the cognitive dissonance between fragments and files since
fragments will no longer include references to scan properties.
was:
Currently: a fragment is a product of a scan; it is a lazy collection of scan
tasks corresponding to a data source which is logically singular (like a single
file, a single row group, ...). It would be more useful if instead a fragment
were the direct object of a scan; one scans a fragment (or a collection of
fragments):
# Remove {{ScanOptions}} from Fragment's properties and move it into
{{Fragment::Scan}} parameters.
# Remove {{ScanOptions}} from {{Dataset::GetFragments}}. We can provide an
overload to support predicate pushdown in FileSystemDataset and UnionDataset
{{Dataset::GetFragments(std::shared_ptr<Expression> predicate)}}.
# Expose lazy accessor to Fragment::physical_schema()
This will lessen the cognitive dissonance between fragments and files since
fragments will no longer include references to scan properties.
> [C++][Dataset] Untangle Dataset, Fragment and ScanOptions
> ---------------------------------------------------------
>
> Key: ARROW-8065
> URL: https://issues.apache.org/jira/browse/ARROW-8065
> Project: Apache Arrow
> Issue Type: Improvement
> Components: C++ - Dataset
> Reporter: Francois Saint-Jacques
> Priority: Major
>
> Currently: a fragment is a product of a scan; it is a lazy collection of scan
> tasks corresponding to a data source which is logically singular (like a
> single file, a single row group, ...). It would be more useful if instead a
> fragment were the direct object of a scan; one scans a fragment (or a
> collection of fragments):
> # Remove {{ScanOptions}} from Fragment's properties and move it into
> {{Fragment::Scan}} parameters.
> # Remove {{ScanOptions}} from {{Dataset::GetFragments}}. We can provide an
> overload to support predicate pushdown in FileSystemDataset and UnionDataset
> {{Dataset::GetFragments(std::shared_ptr<Expression> predicate)}}.
> # Expose lazy accessor to Fragment::physical_schema()
> # Consolidate ScanOptions and ScanContext
> This will lessen the cognitive dissonance between fragments and files since
> fragments will no longer include references to scan properties.
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