Expose builder buffer capacity accessors#10342
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Weijun-H
marked this pull request as ready for review
July 14, 2026 14:30
Jefffrey
approved these changes
Jul 15, 2026
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thanks @Weijun-H, @rluvaton & @Rich-T-kid |
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Which issue does this PR close?
Rationale for this change
Downstream memory accounting sometimes needs to measure the allocated capacity currently retained by Arrow array builders, including allocation slack after buffer growth. Existing slice accessors expose initialized data, but not the underlying values, offsets, or validity-buffer capacity.
What changes are included in this PR?
This adds read-only capacity accessors for existing builder internals:
GenericByteBuilder::{values_capacity, offsets_capacity, validity_capacity}GenericListBuilder::{offsets_capacity, validity_capacity}PrimitiveBuilder::validity_capacityStructBuilder::validity_capacityThe methods only read existing builder state and do not change append, reserve, finish, or resize behavior.
Are these changes tested?
No behavior-specific tests are added because these methods only expose existing capacity fields through read-only forwarding accessors. Existing arrow-array builder tests were run unchanged, and the new public API is compile-checked by the crate.
Validated with:
cargo fmt --all -- --checkcargo test -p arrow-array builder --libcargo test -p arrow-array --libcargo +1.96.0 clippy -p arrow-array --all-targets --no-deps -- -D warningsAre there any user-facing changes?
Yes. This adds public read-only capacity accessors on Arrow array builders.