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Allow CDF scans with schema evolution #523

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OussamaSaoudi-db opened this issue Nov 22, 2024 · 2 comments · May be fixed by #554
Open

Allow CDF scans with schema evolution #523

OussamaSaoudi-db opened this issue Nov 22, 2024 · 2 comments · May be fixed by #554
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enhancement New feature or request

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@OussamaSaoudi-db
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Please describe why this is necessary.

TableChanges today asserts that the schema for the entire range be the same. This condition can be relaxed to allow new nullable columns to be added to the start schema, or toggling the nullability for an existing field to true.

Describe the functionality you are proposing.

Schema enforcement at TableChanges construction and during log replay must accept data with a schema that is missing a nullable field and must fill that nullable field in when producing rows.

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@OussamaSaoudi-db OussamaSaoudi-db added the enhancement New feature or request label Nov 22, 2024
@OussamaSaoudi-db OussamaSaoudi-db mentioned this issue Nov 22, 2024
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@OussamaSaoudi-db OussamaSaoudi-db linked a pull request Dec 3, 2024 that will close this issue
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@scovich
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scovich commented Dec 5, 2024

We should also ignore changes in schema metadata -- at least, the user-provided ones that Delta spec doesn't have any opinion about. I'm less clear whether we should tolerate changes in column mapping table properties?

@OussamaSaoudi-db OussamaSaoudi-db mentioned this issue Dec 14, 2024
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@OussamaSaoudi-db
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@scovich Sorry for missing this comment! Seems that the only thing delta checks in the schema is the struct type and the partition columns.

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feat: Add check for schema read compatibility OussamaSaoudi-db/delta-kernel-rs
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@scovich @OussamaSaoudi-db