Cassandra中的结果分页（CQL）
我想知道如何使用Cassandra实现分页 假设我有一个博客。该博客每页最多列出10篇文章。要访问下一篇文章，用户必须单击分页菜单以访问第2页（文章11-20）、第3页（文章21-30）等 使用MySQL下的SQL，我可以执行以下操作：Cassandra中的结果分页（CQL）,cassandra,cql,cql3,datastax-enterprise,Cassandra,Cql,Cql3,Datastax Enterprise,我想知道如何使用Cassandra实现分页 假设我有一个博客。该博客每页最多列出10篇文章。要访问下一篇文章，用户必须单击分页菜单以访问第2页（文章11-20）、第3页（文章21-30）等 使用MySQL下的SQL，我可以执行以下操作： SELECT * FROM posts LIMIT 20,10; LIMIT的第一个参数是从结果集开始的偏移量，第二个参数是要获取的行数。上面的示例返回从第20行开始的10行 如何在CQL中实现相同的效果 我在谷歌上找到了一些解决方案，但所有的解决方案都需要“
SELECT * FROM posts LIMIT 20,10;
我在谷歌上找到了一些解决方案，但所有的解决方案都需要“上一次查询的最后结果”。“下一步”按钮可以分页到另一个10个结果集，但是如果我想从第1页跳到第5页怎么办？尝试使用CQL中的令牌函数： 另一个建议是，如果您使用DSE，solr支持深度分页：
如果您使用的是Cassandra 2.0+，则不需要使用代币 卡桑德拉2.0具有自动分页功能。 它不再使用令牌函数来创建分页，而是一个内置功能 现在，开发人员可以迭代整个结果集，而不必关心它的大小是否大于内存。当客户机代码迭代结果时，可以提取一些额外的行，而删除旧的行 在Java中，请注意SELECT语句返回所有行，并且检索的行数设置为100 我在这里展示了一个简单的语句，但是同样的代码可以用一个准备好的语句编写，再加上一个绑定语句。如果不需要，可以禁用自动分页。测试各种获取大小设置也很重要，因为您希望保持足够小的内存，但不要太小，以至于需要多次往返数据库。查看博客文章，了解分页如何在服务器端工作 语句stmt=newsimplestatement( “从原始天气数据中选择*” +“其中wsid='725474:99999'” +“年份=2005年，月份=6”）； stmt.setFetchSize（24）； ResultSet rs=session.execute（stmt）； 迭代器iter=rs.Iterator（）； 而（！rs.isFullyFetched（））{ rs.fetchmoresults（）； 行=iter.next（）； 系统输出打印项次（行）； }
手动分页 驱动程序公开PagingState对象，该对象表示获取最后一页时我们在结果集中的位置：
ResultSet resultSet = session.execute("your query");
// iterate the result set...
PagingState pagingState = resultSet.getExecutionInfo().getPagingState();
String string = pagingState.toString();
byte[] bytes = pagingState.toBytes();
PagingState pagingState = PagingState.fromString(string);
Statement st = new SimpleStatement("your query");
st.setPagingState(pagingState);
ResultSet rs = session.execute(st);
<?php
$limit = 10;
$offset = 20;
$cluster = Cassandra::cluster()->withContactPoints('127.0.0.1')->build();
$session = $cluster->connect("simplex");
$statement = new Cassandra\SimpleStatement("SELECT * FROM paging_entries Limit ".($limit+$offset));
$result = $session->execute($statement, new Cassandra\ExecutionOptions(array('page_size' => $offset)));
// Now $result has all rows till "$offset" which we can skip and jump to next page to fetch "$limit" rows.
while ($result->pagingStateToken()) {
$result = $session->execute($statement, new Cassandra\ExecutionOptions($options = array('page_size' => $limit,'paging_state_token' => $result->pagingStateToken())));
foreach ($result as $row) {
printf("key: '%s' value: %d\n", $row['key'], $row['value']);
}
}
?>
- 简单用户列表代码
- 在下一页和上一页状态之间导航
- 易于复制
nextprevious //for the next flow
//if (result.nextPage) {
// Retrieve the following pages:
// the same row handler from above will be used
// result.nextPage();
//}
var userModel = require('/models/users');
public.get('/users', users);
public.post('/users', filterUsers);
var users = function* () {//get request
var data = {};
var pageState = { "next": "", "previous": "" };
try {
var userCount = yield userModel.Count();//count all users with basic count query
var currentPage = 1;
var pager = yield generatePaging(currentPage, userCount, pagingMaxLimit);
var userList = yield userModel.List(pager);
data.pageNumber = currentPage;
data.TotalPages = pager.TotalPages;
console.log('--------------what now--------------');
data.pageState_next = userList.pageStates.next;
data.pageState_previous = userList.pageStates.previous;
console.log("next ", data.pageState_next);
console.log("previous ", data.pageState_previous);
data.previousStates = null;
data.isPrevious = false;
if ((userCount / pagingMaxLimit) > 1) {
data.isNext = true;
}
data.userList = userList;
data.totalRecords = userCount;
console.log('--------------------userList--------------------', data.userList);
//pass to html template
}
catch (e) {
console.log("err ", e);
log.info("userList error : ", e);
}
this.body = this.stream('./views/userList.marko', data);
this.type = 'text/html';
};
//post filter and get list
var filterUsers = function* () {
console.log("<------------------Form Post Started----------------->");
var data = {};
var totalCount;
data.isPrevious = true;
data.isNext = true;
var form = this.request.body;
console.log("----------------formdata--------------------", form);
var currentPage = parseInt(form.hdpagenumber);//page number hidden in html
console.log("-------before current page------", currentPage);
var pageState = null;
try {
var statesArray = [];
if (form.hdallpageStates && form.hdallpageStates !== '') {
statesArray = form.hdallpageStates.split(',');
}
console.log(statesArray);
//develop stack to track paging states
if (form.hdpagestateRequest === 'next') {
console.log('--------------------------next---------------------');
currentPage = currentPage + 1;
statesArray.push(form.hdpageState_next);
pageState = form.hdpageState_next;
}
else if (form.hdpagestateRequest === 'previous') {
console.log('--------------------------pre---------------------');
currentPage = currentPage - 1;
var p_st = statesArray.length - 2;//second last index
console.log('this index of array to be removed ', p_st);
pageState = statesArray[p_st];
statesArray.splice(p_st, 1);
//pageState = statesArray.pop();
}
else if (form.hdispaging === 'false') {
currentPage = 1;
pageState = null;
statesArray = [];
}
data.previousStates = statesArray;
console.log("paging true");
totalCount = yield userModel.Count();
var pager = yield generatePaging(form.hdpagenumber, totalCount, pagingMaxLimit);
data.pageNumber = currentPage;
data.TotalPages = pager.TotalPages;
//filter function - not yet constructed
var searchUsers = yield userModel.searchList(pager, pageState);
data.usersList = searchUsers;
if (searchUsers.pageStates) {
data.pageStates = searchUsers.pageStates;
data.next = searchUsers.nextPage;
data.pageState_next = searchUsers.pageStates.next;
data.pageState_previous = searchUsers.pageStates.previous;
//show previous and next buttons accordingly
if (currentPage == 1 && pager.TotalPages > 1) {
data.isPrevious = false;
data.isNext = true;
}
else if (currentPage == 1 && pager.TotalPages <= 1) {
data.isPrevious = false;
data.isNext = false;
}
else if (currentPage >= pager.TotalPages) {
data.isPrevious = true;
data.isNext = false;
}
else {
data.isPrevious = true;
data.isNext = true;
}
}
else {
data.isPrevious = false;
data.isNext = false;
}
console.log("response ", searchUsers);
data.totalRecords = totalCount;
//pass to html template
}
catch (e) {
console.log("err ", e);
log.info("user list error : ", e);
}
console.log("<------------------Form Post Ended----------------->");
this.body = this.stream('./views/userList.marko', data);
this.type = 'text/html';
};
//Paging function
var generatePaging = function* (currentpage, count, pageSizeTemp) {
var paging = new Object();
var pagesize = pageSizeTemp;
var totalPages = 0;
var pageNo = currentpage == null ? null : currentpage;
var skip = pageNo == null ? 0 : parseInt(pageNo - 1) * pagesize;
var pageNumber = pageNo != null ? pageNo : 1;
totalPages = pagesize == null ? 0 : Math.ceil(count / pagesize);
paging.skip = skip;
paging.limit = pagesize;
paging.pageNumber = pageNumber;
paging.TotalPages = totalPages;
return paging;
};
var clientdb = require('../utils/cassandradb')();
var Users = function (options) {
//this.init();
_.assign(this, options);
};
Users.List = function* (limit) {//first time
var myresult; var res = [];
res.pageStates = { "next": "", "previous": "" };
const options = { prepare: true, fetchSize: limit };
console.log('----------did i appeared first?-----------');
yield new Promise(function (resolve, reject) {
clientdb.eachRow('SELECT * FROM users_lookup_history', [], options, function (n, row) {
console.log('----paging----rows');
res.push(row);
}, function (err, result) {
if (err) {
console.log("error ", err);
}
else {
res.pageStates.next = result.pageState;
res.nextPage = result.nextPage;//next page function
}
resolve(result);
});
}).catch(function (e) {
console.log("error ", e);
}); //promise ends
console.log('page state ', res.pageStates);
return res;
};
Users.searchList = function* (pager, pageState) {//paging filtering
console.log("|------------Query Started-------------|");
console.log("pageState if any ", pageState);
var res = [], myresult;
res.pageStates = { "next": "" };
var query = "SELECT * FROM users_lookup_history ";
var params = [];
console.log('current pageState ', pageState);
const options = { pageState: pageState, prepare: true, fetchSize: pager.limit };
console.log('----------------did i appeared first?------------------');
yield new Promise(function (resolve, reject) {
clientdb.eachRow(query, [], options, function (n, row) {
console.log('----Users paging----rows');
res.push(row);
}, function (err, result) {
if (err) {
console.log("error ", err);
}
else {
res.pageStates.next = result.pageState;
res.nextPage = result.nextPage;
}
//for the next flow
//if (result.nextPage) {
// Retrieve the following pages:
// the same row handler from above will be used
// result.nextPage();
//}
resolve(result);
});
}).catch(function (e) {
console.log("error ", e);
info.log('something');
}); //promise ends
console.log('page state ', pageState);
console.log("|------------Query Ended-------------|");
return res;
};
<div class="box-footer clearfix">
<ul class="pagination pagination-sm no-margin pull-left">
<if test="data.isPrevious == true">
<li><a class='submitform_previous' href="">Previous</a></li>
</if>
<if test="data.isNext == true">
<li><a class="submitform_next" href="">Next</a></li>
</if>
</ul>
<ul class="pagination pagination-sm no-margin pull-right">
<li>Total Records : $data.totalRecords</li>
<li> | Total Pages : $data.TotalPages</li>
<li> | Current Page : $data.pageNumber</li>
</ul>
</div>