Writing with large arrow types in MERGE #1753
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enhancement
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Blajda
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Nov 19, 2023
# Description This refactors the merge operation to use DataFusion's DataFrame and LogicalPlan APIs The NLJ is eliminated and the query planner can pick the optimal join operator. This also enables the operation to use multiple threads and should result in significant speed up. Merge is still limited to using a single thread in some area. When collecting benchmarks, I encountered multiple OoM issues with Datafusion's hash join implementation. There are multiple tickets upstream open regarding this. For now, I've limited the number of partitions to just 1 to prevent this. Predicates passed as SQL are also easier to use now. Manual casting was required to ensure data types were aligned. Now the logical plan will perform type coercion when optimizing the plan. # Related Issues - enhances #850 - closes #1790 - closes #1753
ion-elgreco
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Nov 20, 2023
# Description This refactors the merge operation to use DataFusion's DataFrame and LogicalPlan APIs The NLJ is eliminated and the query planner can pick the optimal join operator. This also enables the operation to use multiple threads and should result in significant speed up. Merge is still limited to using a single thread in some area. When collecting benchmarks, I encountered multiple OoM issues with Datafusion's hash join implementation. There are multiple tickets upstream open regarding this. For now, I've limited the number of partitions to just 1 to prevent this. Predicates passed as SQL are also easier to use now. Manual casting was required to ensure data types were aligned. Now the logical plan will perform type coercion when optimizing the plan. # Related Issues - enhances delta-io#850 - closes delta-io#1790 - closes delta-io#1753
ion-elgreco
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Nov 20, 2023
# Description This refactors the merge operation to use DataFusion's DataFrame and LogicalPlan APIs The NLJ is eliminated and the query planner can pick the optimal join operator. This also enables the operation to use multiple threads and should result in significant speed up. Merge is still limited to using a single thread in some area. When collecting benchmarks, I encountered multiple OoM issues with Datafusion's hash join implementation. There are multiple tickets upstream open regarding this. For now, I've limited the number of partitions to just 1 to prevent this. Predicates passed as SQL are also easier to use now. Manual casting was required to ensure data types were aligned. Now the logical plan will perform type coercion when optimizing the plan. # Related Issues - enhances delta-io#850 - closes delta-io#1790 - closes delta-io#1753
ion-elgreco
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Nov 20, 2023
# Description This refactors the merge operation to use DataFusion's DataFrame and LogicalPlan APIs The NLJ is eliminated and the query planner can pick the optimal join operator. This also enables the operation to use multiple threads and should result in significant speed up. Merge is still limited to using a single thread in some area. When collecting benchmarks, I encountered multiple OoM issues with Datafusion's hash join implementation. There are multiple tickets upstream open regarding this. For now, I've limited the number of partitions to just 1 to prevent this. Predicates passed as SQL are also easier to use now. Manual casting was required to ensure data types were aligned. Now the logical plan will perform type coercion when optimizing the plan. # Related Issues - enhances delta-io#850 - closes delta-io#1790 - closes delta-io#1753
ion-elgreco
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Nov 24, 2023
…iter/merge (#1820) # Description This ports some functionality that @stinodego and I had worked on in Polars. Where we converted a pyarrow schema to a compatible delta schema. It converts the following: - uint -> int - timestamp(any timeunit) -> timestamp(us) I adjusted the functionality to do schema conversion from large to normal when necessary, which is still needed in MERGE as workaround #1753. Additional things I've added: - Schema conversion for every input in write_deltalake/merge - Add Pandas dataframe conversion - Add Pandas dataframe as input in merge # Related Issue(s) - closes #686 - closes #1467 --------- Co-authored-by: Will Jones <[email protected]>
ion-elgreco
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Nov 25, 2023
…iter/merge (delta-io#1820) This ports some functionality that @stinodego and I had worked on in Polars. Where we converted a pyarrow schema to a compatible delta schema. It converts the following: - uint -> int - timestamp(any timeunit) -> timestamp(us) I adjusted the functionality to do schema conversion from large to normal when necessary, which is still needed in MERGE as workaround delta-io#1753. Additional things I've added: - Schema conversion for every input in write_deltalake/merge - Add Pandas dataframe conversion - Add Pandas dataframe as input in merge - closes delta-io#686 - closes delta-io#1467 --------- Co-authored-by: Will Jones <[email protected]>
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Description
It seems it's not possible to write with large arrow types in
.merge()yet, however there is write support withwrite_deltalake(large_types=True), we should add this also in merge.Use Case
Converting Polars dataframes to arrow and then merging immediately instead of casting to normal arrow types which may not fit if the arrays are too large.
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