摘要：cassandra的集合类型tourist创建带有复杂cell的user表CREATE TABLE ks.user ( id int PRIMARY KEY, addr map<tcass

cassandra的集合类型tourist创建带有复杂cell的user表CREATE TABLE ks.user ( id int PRIMARY KEY, addr map<t

cassandra的集合类型tourist

创建带有复杂cell的user表

CREATE TABLE ks.user (    id int PRIMARY KEY,    addr map<text, frozen<set<text>>>,    complex map<text, frozen<map<text, text>>>,    listcolumn list<text>,    setcolumn set<text>)

插入一些数据后，查询数据如下

cassandra@cqlsh:ks> select * from user; id | addr                                           | complex                          | listcolumn      | setcolumn----+------------------------------------------------+----------------------------------+-----------------+-----------------  1 | {'bj': {'ba', 'bb'}, 'shanghai': {'sa', 'sb'}} | {'bj': {'ka': 'va', 'kb': 'vb'}} | ['a', 'b', 'c'] | {'a', 'b', 'c'}

执行bin/nodetool flush,生成sst

查看sst，文本输出

tools/bin/sstabledump /data/data2/ks/user-a92ce790a8ff11e99a3d8963a5d3f9b4/md-17-big-Data.db[{  "partition" : {    "key" : [ "1" ],    "position" : 0  },  "rows" : [    {      "type" : "row",      "position" : 233,      "liveness_info" : { "tstamp" : "2019-07-18T02:43:36.011497Z" },      "cells" : [        { "name" : "addr", "deletion_info" : { "marked_deleted" : "2019-07-18T02:43:36.011496Z", "local_delete_time" : "2019-07-18T02:43:36Z" } },        { "name" : "addr", "path" : [ "bj" ], "value" : ["ba", "bb"] },        { "name" : "addr", "path" : [ "shanghai" ], "value" : ["sa", "sb"] },        { "name" : "complex", "deletion_info" : { "marked_deleted" : "2019-07-18T02:47:55.888562Z", "local_delete_time" : "2019-07-18T02:47:55Z" } },        { "name" : "complex", "path" : [ "bj" ], "value" : {"ka": "va", "kb": "vb"}, "tstamp" : "2019-07-18T02:47:55.888563Z" },        { "name" : "listcolumn", "deletion_info" : { "marked_deleted" : "2019-07-18T02:56:09.386468Z", "local_delete_time" : "2019-07-18T02:56:09Z" } },        { "name" : "listcolumn", "path" : [ "982493f0-a907-11e9-9a3d-8963a5d3f9b4" ], "value" : "a", "tstamp" : "2019-07-18T02:56:09.386469Z" },        { "name" : "listcolumn", "path" : [ "982493f1-a907-11e9-9a3d-8963a5d3f9b4" ], "value" : "b", "tstamp" : "2019-07-18T02:56:09.386469Z" },        { "name" : "listcolumn", "path" : [ "982493f2-a907-11e9-9a3d-8963a5d3f9b4" ], "value" : "c", "tstamp" : "2019-07-18T02:56:09.386469Z" },        { "name" : "setcolumn", "deletion_info" : { "marked_deleted" : "2019-07-18T02:55:03.280578Z", "local_delete_time" : "2019-07-18T02:55:03Z" } },        { "name" : "setcolumn", "path" : [ "a" ], "value" : "", "tstamp" : "2019-07-18T02:55:03.280579Z" },        { "name" : "setcolumn", "path" : [ "b" ], "value" : "", "tstamp" : "2019-07-18T02:55:03.280579Z" },        { "name" : "setcolumn", "path" : [ "c" ], "value" : "", "tstamp" : "2019-07-18T02:55:03.280579Z" }      ]    }  ]}

底层的集合是通过cellName+path唯一标记一个元素的。

重点看下addr及complex列， 这两列是嵌套map

{ "name" : "complex", "path" : [ "bj" ], "value" : {"ka": "va", "kb": "vb"}, "tstamp" : "2019-07-18T02:47:55.888563Z" },

但对于子map frozen<map<text, text>> 基本上是当做blob存储的，不能操作map中的子元素，这也是frozen语义。

c*是无主架构，可以多node并发写同一个集合，那如何解决冲突？答案是底层最小存储单元并不是cell，而是cell+path唯一标记的element,依赖于cell&path做单元合并的，以cell timestamp最新作为最终值

删除setcolumn中一个元素

cassandra@cqlsh:ks> update user set setcolumn = setcolumn - {'a'} where id =1;

flush后，查看刚生成的sstable, setcolumn.a写入了一个delete_info

[root@Cassandra8c32GTest005 cassandra]# tools/bin/sstabledump /data/data2/ks/user-a92ce790a8ff11e99a3d8963a5d3f9b4/md-19-big-Data.db[{  "partition" : {    "key" : [ "1" ],    "position" : 0  },  "rows" : [    {      "type" : "row",      "position" : 27,      "cells" : [        { "name" : "setcolumn", "path" : [ "a" ], "deletion_info" : { "local_delete_time" : "2019-07-18T10:03:17Z" },          "tstamp" : "2019-07-18T10:03:17.038519Z"        }      ]    }  ]}]

做下手工merge，可以发现setcolumn.a value没了，写入了delete_info

bin/nodetool compacttools/bin/sstabledump /data/data2/ks/user-a92ce790a8ff11e99a3d8963a5d3f9b4/md-22-big-Data.db[  {    "partition" : {      "key" : [ "1" ],      "position" : 0    },    "rows" : [      {        "type" : "row",        "position" : 236,        "liveness_info" : { "tstamp" : "2019-07-18T02:43:36.011497Z" },        "cells" : [          { "name" : "addr", "deletion_info" : { "marked_deleted" : "2019-07-18T02:43:36.011496Z", "local_delete_time" : "2019-07-18T02:43:36Z" } },          { "name" : "addr", "path" : [ "bj" ], "value" : ["ba", "bb"] },          { "name" : "addr", "path" : [ "shanghai" ], "value" : ["sa", "sb"] },          { "name" : "complex", "deletion_info" : { "marked_deleted" : "2019-07-18T02:47:55.888562Z", "local_delete_time" : "2019-07-18T02:47:55Z" } },          { "name" : "complex", "path" : [ "bj" ], "value" : {"ka": "va", "kb": "vb"}, "tstamp" : "2019-07-18T02:47:55.888563Z" },          { "name" : "listcolumn", "deletion_info" : { "marked_deleted" : "2019-07-18T02:56:09.386468Z", "local_delete_time" : "2019-07-18T02:56:09Z" } },          { "name" : "listcolumn", "path" : [ "982493f0-a907-11e9-9a3d-8963a5d3f9b4" ], "value" : "a", "tstamp" : "2019-07-18T02:56:09.386469Z" },          { "name" : "listcolumn", "path" : [ "982493f1-a907-11e9-9a3d-8963a5d3f9b4" ], "value" : "b", "tstamp" : "2019-07-18T02:56:09.386469Z" },          { "name" : "listcolumn", "path" : [ "982493f2-a907-11e9-9a3d-8963a5d3f9b4" ], "value" : "c", "tstamp" : "2019-07-18T02:56:09.386469Z" },          { "name" : "setcolumn", "deletion_info" : { "marked_deleted" : "2019-07-18T02:55:03.280578Z", "local_delete_time" : "2019-07-18T02:55:03Z" } },          { "name" : "setcolumn", "path" : [ "a" ], "deletion_info" : { "local_delete_time" : "2019-07-18T10:03:17Z" },            "tstamp" : "2019-07-18T10:03:17.038519Z"          },          { "name" : "setcolumn", "path" : [ "b" ], "value" : "", "tstamp" : "2019-07-18T02:55:03.280579Z" },          { "name" : "setcolumn", "path" : [ "c" ], "value" : "", "tstamp" : "2019-07-18T02:55:03.280579Z" }        ]      }    ]  }

试试删除setcolumn整列

update user set setcolumn = null where id =1;

刷sst，执行nodetool compact， 使用dump工具查看，setcolumn之前的子元素全部消失了。

tools/bin/sstabledump  /data/data2/ks/user-a92ce790a8ff11e99a3d8963a5d3f9b4/md-27-big-Data.db[  {    "partition" : {      "key" : [ "1" ],      "position" : 0    },    "rows" : [      {        "type" : "row",        "position" : 210,        "liveness_info" : { "tstamp" : "2019-07-18T02:43:36.011497Z" },        "cells" : [          { "name" : "addr", "deletion_info" : { "marked_deleted" : "2019-07-18T02:43:36.011496Z", "local_delete_time" : "2019-07-18T02:43:36Z" } },          { "name" : "addr", "path" : [ "bj" ], "value" : ["ba", "bb"] },          { "name" : "addr", "path" : [ "shanghai" ], "value" : ["sa", "sb"] },          { "name" : "complex", "deletion_info" : { "marked_deleted" : "2019-07-18T02:47:55.888562Z", "local_delete_time" : "2019-07-18T02:47:55Z" } },          { "name" : "complex", "path" : [ "bj" ], "value" : {"ka": "va", "kb": "vb"}, "tstamp" : "2019-07-18T02:47:55.888563Z" },          { "name" : "listcolumn", "deletion_info" : { "marked_deleted" : "2019-07-18T02:56:09.386468Z", "local_delete_time" : "2019-07-18T02:56:09Z" } },          { "name" : "listcolumn", "path" : [ "982493f0-a907-11e9-9a3d-8963a5d3f9b4" ], "value" : "a", "tstamp" : "2019-07-18T02:56:09.386469Z" },          { "name" : "listcolumn", "path" : [ "982493f1-a907-11e9-9a3d-8963a5d3f9b4" ], "value" : "b", "tstamp" : "2019-07-18T02:56:09.386469Z" },          { "name" : "listcolumn", "path" : [ "982493f2-a907-11e9-9a3d-8963a5d3f9b4" ], "value" : "c", "tstamp" : "2019-07-18T02:56:09.386469Z" },          { "name" : "setcolumn", "deletion_info" : { "marked_deleted" : "2019-07-18T10:11:06.966534Z", "local_delete_time" : "2019-07-18T10:11:06Z" } }        ]      }    ]  }

总结

cassandra 宽表模型是将列打平存储成一个个cell，对于集合类型，相当于把cell再打平成path存储，整个表格相当于是一个双层结构。同时集合cell有自己的deleteTime，下层的path也有自己的deleteTime， ts等。

原文链接：https://yq.aliyun.com/articles/715496?utm_content=g_1000073204

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