[ARROW-7281] [C++] AdaptiveIntBuilder::length() does not consider pending_pos_.

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.15.1
• Fix Version/s: 0.16.0
• Component/s: C++
• Labels: pull-request-available
• External issue URL: https://github.com/apache/arrow/issues/23570
• Assignee: Antoine Pitrou
• Reporter: Adam Hooper
• Created: 29/Nov/19 22:43
• Updated: 11/Jan/23 07:52
• Resolved: 14/Jan/20 19:20

Description

arrow::AdaptiveIntBuilder builder(arrow::default_memory_pool());
builder.Append(1);
std::cout << builder.length() << std::endl;

Expected output: 1
Actual output: 0

I imagine this regression came with https://github.com/apache/arrow/pull/3040

My use case: I'm building a JSON parser that appends "records" (JSON Objects mapping key=>value) to Arrow columns (each key gets an ArrayBuilder). Not all JSON Objects contain all keys; so builder.Append() isn't always called. So on a subsequent row, I want to add nulls for every append that was skipped: builder.AppendNulls(row - builder.length()); builder.Append(value). This fails because builder.length() is wrong.

Annoying but simple workaround: I maintain a separate length value alongside builder.

Issue Links

• links to: GitHub Pull Request #6174