ARROW-5981: [C++] Propagate errors from MemoTable to DictionaryBuilder

[pitrou]

No description provided.

[pitrou]

This incurs a noticeable slowdown in building integer dictionaries (10-20% depending on the benchmark). String dictionaries are not affected.

[github-actions]

https://issues.apache.org/jira/browse/ARROW-5981

[wesm]

Makes me wonder if there should not also be a set of "unsafe" APIs that skip error propagation and instead set a "global" error state in the memo table instance. So after a sequence of multiple operations you can check if any error occurred. (Just thinking out loud)

[pitrou]

Makes me wonder if there should not also be a set of "unsafe" APIs that skip error propagation and instead set a "global" error state in the memo table instance.

i'll try that out.

[pitrou]

Ok, after trying it out, I don't think it's worthwhile. AdaptiveIntBuilder can fail at almost any point (because it can double the stored integer width dynamically). In general, even if we don't check errors when inserting values into the memo table, we'll check errors somewhere else, when growing another buffer somewhere.

[wesm]

OK, I figure if it shows up in a performance critical context in the future this can be analyzed more closely for use-case-specific optimizations