Harshavardhana 7e1661f4fa Performance improvements to SELECT API on certain query operations (#6752) ... This improves the performance of certain queries dramatically, such as 'count(*)' etc. Without this PR ``` ~ time mc select --query "select count(*) from S3Object" myminio/sjm-airlines/star2000.csv.gz 2173762 real 0m42.464s user 0m0.071s sys 0m0.010s ``` With this PR ``` ~ time mc select --query "select count(*) from S3Object" myminio/sjm-airlines/star2000.csv.gz 2173762 real 0m17.603s user 0m0.093s sys 0m0.008s ``` Almost a 250% improvement in performance. This PR avoids a lot of type conversions and instead relies on raw sequences of data and interprets them lazily. ``` benchcmp old new benchmark old ns/op new ns/op delta BenchmarkSQLAggregate_100K-4 551213 259782 -52.87% BenchmarkSQLAggregate_1M-4 6981901985 2432413729 -65.16% BenchmarkSQLAggregate_2M-4 13511978488 4536903552 -66.42% BenchmarkSQLAggregate_10M-4 68427084908 23266283336 -66.00% benchmark old allocs new allocs delta BenchmarkSQLAggregate_100K-4 2366 485 -79.50% BenchmarkSQLAggregate_1M-4 47455492 21462860 -54.77% BenchmarkSQLAggregate_2M-4 95163637 43110771 -54.70% BenchmarkSQLAggregate_10M-4 476959550 216906510 -54.52% benchmark old bytes new bytes delta BenchmarkSQLAggregate_100K-4 1233079 1086024 -11.93% BenchmarkSQLAggregate_1M-4 2607984120 557038536 -78.64% BenchmarkSQLAggregate_2M-4 5254103616 1128149168 -78.53% BenchmarkSQLAggregate_10M-4 26443524872 5722715992 -78.36% ```		2018-11-14 15:55:10 -08:00
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csv	Performance improvements to SELECT API on certain query operations (#6752)	2018-11-14 15:55:10 -08:00
json	Performance improvements to SELECT API on certain query operations (#6752)	2018-11-14 15:55:10 -08:00
errors.go	SQL select query for CSV/JSON (#6648)	2018-10-22 12:12:22 -07:00
helpers.go	SQL select query for CSV/JSON (#6648)	2018-10-22 12:12:22 -07:00
select.go	Performance improvements to SELECT API on certain query operations (#6752)	2018-11-14 15:55:10 -08:00