Resolve tiny differences between Anserini and Pyserini on MS MARCO: query iteration order

If we look at the Python replications: https://github.com/castorini/pyserini/blob/master/docs/pypi-replication.md Compared against Anserini replications: e.g., https://github.com/castorini/anserini/blob/master/docs/experiments-msmarco-doc-leaderboard.md

We’ll note tiny differences - e.g., for MS MARCO doc, baselines - pyserini:

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MRR @100: 0.2770296928568709
QueriesRanked: 5193
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Compared to anserini:

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MRR @100: 0.2770296928568702
QueriesRanked: 5193
#####################

Previously, we tracked it down issue #257

I’d like to fix it so get identical results moving forward - my proposed fix is a bit janky, but it’ll work: Let’s just store, in Python code, an array of integers corresponding to ids of the queries in the original queries file. When we’re iterating over the dataset in pyserini.search, we just follow the order of the integers.

Slightly better, we introduce a new query iterator abstraction and hide this implementation detail in there. So the query iterator would take in the current dictionary, and an optional array holding the iteration order.

Thoughts @MXueguang? I was thinking you could work on this?

[MXueguang]

i see. so query iterator takes cur_dict and order_array and yield (id, text) pairs

[lintool]

Closed by #309