S3 SQL 限制运算符

SQL 限制运算符用于限制查询处理的行数。

达到用户设置的限制时， Ceph Object Gateway 将停止访存其他块。

以下是 CSV ， Parquet 和 JSON 的 SQL 限制运算符的示例。

CSV

[cephuser@host ~]$ aws s3api --endpoint-url http://extensa027.ceph.ibm.com:80 select-object-content  --bucket bkt1 --key placement_data1 --expression-type 'SQL' --input-serialization '{"CSV": {"FileHeaderInfo": "USE"}, "CompressionType": "NONE"}' --output-serialization '{"CSV": {}}' --expression "select * from s3object limit 10;" 

/dev/stdout
1,M,67.00,Others,91.00,Others,Commerce,58.00,Sci&Tech,No,55,Mkt&HR,58.8,Placed,270000
2,M,79.33,Central,78.33,Others,Science,77.48,Sci&Tech,Yes,86.5,Mkt&Fin,66.28,Placed,200000
3,M,65.00,Central,68.00,Central,Arts,64.00,Comm&Mgmt,No,75,Mkt&Fin,57.8,Placed,250000
4,M,56.00,Central,52.00,Central,Science,52.00,Sci&Tech,No,66,Mkt&HR,59.43,Not Placed,
5,M,85.80,Central,73.60,Central,Commerce,73.30,Comm&Mgmt,No,96.8,Mkt&Fin,55.5,Placed,425000
6,M,55.00,Others,49.80,Others,Science,67.25,Sci&Tech,Yes,55,Mkt&Fin,51.58,Not Placed,
7,F,46.00,Others,49.20,Others,Commerce,79.00,Comm&Mgmt,No,74.28,Mkt&Fin,53.29,Not Placed,
8,M,82.00,Central,64.00,Central,Science,66.00,Sci&Tech,Yes,67,Mkt&Fin,62.14,Placed,252000
9,M,73.00,Central,79.00,Central,Commerce,72.00,Comm&Mgmt,No,91.34,Mkt&Fin,61.29,Placed,231000
10,M,58.00,Central,70.00,Central,Commerce,61.00,Comm&Mgmt,No,54,Mkt&Fin,52.21,Not Placed,

Parquet

[cephuser@extensa022 ~]$ aws s3api --endpoint-url http://extensa027.ceph.ibm.com:80 select-object-content  --bucket parquetbkt2 --key smallfile --expression-type 'SQL' --input-serialization '{"Parquet": {}, "CompressionType": "NONE"}' --output-serialization '{"CSV": {}}'  --expression "select * from s3object limit 5;" 

/dev/stdout
4819,90340852.424672872,exile,0
4638,95603700.561133489,contradiction,1
1667,99440023.596563846,slam,2
7113,33213151.245887276,publisher,3
2872,43556628.954562038,demonstrate,4

JSON

[cephuser@extensa027 ~]$ aws s3api --endpoint-url http://extensa027.ceph.ibm.com:80 select-object-content  --bucket bkt1 --key books_data.json --expression-type 'SQL' --input-serialization '{"JSON": {"Type": "DOCUMENT"}, "CompressionType": "NONE"}' --output-serialization '{"CSV": {}}' --expression "select * from s3object[*];" 

/dev/stdout
id. : 1091
authors.name. : Makoto Satoh
authors.org. : Shinshu University
authors.id. : 2312688602
authors.name. : Ryo Muramatsu
authors.org. : Shinshu University
authors.id. : 2482909946
title. : Preliminary Design of a Network Protocol Learning Tool Based on the Comprehension of High School Students: Design by an Empirical Study Using a Simple Mind Map
year. : 2013
#=== 0 ===#
id. : 1388
authors.name. : Mizue Kayama
authors.org. : Shinshu University
authors.id. : 2128134587
authors.name. : Pranava K. Jha
authors.id. : 2718958994
authors.name. : Kazunori Itoh
authors.org. : Shinshu University
authors.id. : 2101782692
title. : Further Results on Independence in Direct-Product Graphs.
year. : 2000
#=== 1 ===#
id. : 5781
authors.name. : Jovan Dj. Golic
authors.id. : 1237859792
authors.name. : Guglielmo Morgari
authors.id. : 220887178
title. : Vectorial fast correlation attacks.
year. : 2004
#=== 2 ===#
id. : 6522
authors.name. : Güzin Ulutas
authors.org. : Karadeniz Technical Univ.
authors.id. : 2022192081
authors.name. : Mustafa Ulutas
authors.org. : Karadeniz Technical Univ.
authors.id. : 2023460672
authors.name. : Vasif V. Nabiyev
authors.org. : Karadeniz Technical Univ.
authors.id. : 2174205032
title. : Improved Secret Image Sharing Method By Encoding Shared Values With Authentication Bits
year. : 2011
#=== 3 ===#