It's the first time I use reduce with promise, and it's look perfect for my usage.
However, I'm trying to use reduce to iterate more than the original size of my array (call reduce_array in my example).
In fact, in this example, methodThatReturnsAPromise worth true in certain case, false in other. (in the end it always finish by worth false)
The idea is if results is false then reduce work normaly, and go to the next value (nextId). In the other hand, if results is true,
I have to resolve methodThatReturnsAPromise with the same value again.
I already try differents methods using the index in parameter, or I already try to push again the id in reduce_array but none of that work.
reduce_array.reduce((accumulatorPromise, nextId, index, array) => {
return accumulatorPromise.then((results) => {
//if results === end || result === unknownDomain
//next
//first iteration, results don't exist
if (results) {
if (results === true) {
index++;
return methodThatReturnsAPromise(nextId - 1);
} else {
return methodThatReturnsAPromise(nextId);
}
} else {
return methodThatReturnsAPromise(nextId);
}
})
}, Promise.resolve());
A do/while loop inside a for loop will probably be a lot simpler:
(async () => {
for (const nextId of reduce_array) {
let result;
do {
result = await methodThatReturnsAPromise(nextId);
} while (result !== true);
}
})();
If you had to use reduce, you could put a named function which calls itself recursively inside the reduce callback:
reduce_array.reduce((accumulatorPromise, nextId) => {
return accumulatorPromise.then(() => {
const getThisInfo = () => methodThatReturnsAPromise(nextId)
.then((result) => (
result === true
? getThisInfo()
: null
));
return getThisInfo();
})
}, Promise.resolve());
Which is a bit ugly and not so easy to read. I'd prefer the for loop.
I can't find any code example or docs that answers this:
Achieve almost complete infinite scroll -> unknown # of items, but there is a finite amount that may be infeasible to compute beforehand - e.g. at some point the list needs to stop scrolling
Can I trigger first load of data from within InfiniteScroller/List - it seems you need to pass in a data source that is populated with initial page
I am using this example:
https://github.com/bvaughn/react-virtualized/blob/master/docs/creatingAnInfiniteLoadingList.md
and:
https://github.com/bvaughn/react-virtualized/blob/master/source/InfiniteLoader/InfiniteLoader.example.js
along with CellMeasurer for dynamic height:
https://github.com/bvaughn/react-virtualized/blob/master/source/CellMeasurer/CellMeasurer.DynamicHeightList.example.js
The docs for InfiniteLoader.rowCount say:
"Number of rows in list; can be arbitrary high number if actual number is unknown."
So how do you indicate there are no more rows.
If anyone can post an example using setTimeout() to simulate dynamic loaded data, thanks. I can likely get CellMeasurer working from there.
Edit
This doesn't work the way react-virtualized creator says it should or the infinite loading example implies.
Calls:
render(): rowCount = 1
_rowRenderer(index = 0)
_isRowLoaded(index = 0)
_loadMoreRows(startIndex = 0, stopIndex = 0)
_rowRenderer(index = 0)
end
Do I need to specify a batch size or some other props?
class HistoryBrowser extends React.Component
{
constructor(props,context,updater)
{
super(props,context,updater);
this.eventEmitter = new EventEmitter();
this.eventEmitter.extend(this);
this.state = {
history: []
};
this._cache = new Infinite.CellMeasurerCache({
fixedWidth: true,
minHeight: 50
});
this._timeoutIdMap = {};
_.bindAll(this,'_isRowLoaded','_loadMoreRows','_rowRenderer');
}
render()
{
let rowCount = this.state.history.length ? (this.state.history.length + 1) : 1;
return <Infinite.InfiniteLoader
isRowLoaded={this._isRowLoaded}
loadMoreRows={this._loadMoreRows}
rowCount={rowCount}
>
{({ onRowsRendered, registerChild }) =>
<Infinite.AutoSizer disableHeight>
{({ width }) =>
<Infinite.List
ref={registerChild}
deferredMeasurementCache={this._cache}
height={200}
onRowsRendered={onRowsRendered}
rowCount={rowCount}
rowHeight={this._cache.rowHeight}
rowRenderer={this._rowRenderer}
width={width}
/>}
</Infinite.AutoSizer>}
</Infinite.InfiniteLoader>
}
_isRowLoaded({ index }) {
if (index == 0 && !this.state.history.length)
// No data yet, force load
return false;
}
_loadMoreRows({ startIndex, stopIndex }) {
let self = this;
for (let i = startIndex; i <= stopIndex; i++) {
this.state.history[startIndex] = {loading: true};
}
const timeoutId = setTimeout(() => {
delete this._timeoutIdMap[timeoutId];
for (let i = startIndex; i <= stopIndex; i++) {
self.state.history[i] = {loading: false, text: 'Hi ' + i };
}
promiseResolver();
}, 10000);
this._timeoutIdMap[timeoutId] = true;
let promiseResolver;
return new Promise(resolve => {
promiseResolver = resolve;
});
}
_rowRenderer({ index, key, style }) {
let content;
if (index >= this.state.history.length)
return <div>Placeholder</div>
else if (this.state.history[index].loading) {
content = <div>Loading</div>;
} else {
content = (
<div>Loaded</div>
);
}
return (
<Infinite.CellMeasurer
cache={this._cache}
columnIndex={0}
key={key}
rowIndex={index}
>
<div key={key} style={style}>{content}</div>
</Infinite.CellMeasurer>
);
}
}
The recipe you linked to should be a good starting place. The main thing its missing is an implementation of loadNextPage but that varies from app to app based on how your state/data management code works.
Can I trigger first load of data from within InfiniteScroller/List - it seems you need to pass in a data source that is populated with initial page
This is up to you. IMO it generally makes sense to just fetch the first "page" of records without waiting for InfiniteLoader to ask for them- because you know you'll need them. That being said, if you give InfiniteLoader a rowCount of 1 and then return false from isRowLoaded it should request the first page of records. There are tests confirming this behavior in the react-virtualized GitHub.
The docs for InfiniteLoader.rowCount say: "Number of rows in list; can be arbitrary high number if actual number is unknown."
So how do you indicate there are no more rows.
You stop adding +1 to the rowCount, like the markdown file you linked to mentions:
// If there are more items to be loaded then add an extra row to hold a
loading indicator.
const rowCount = hasNextPage
? list.size + 1
: list.size
I have been stuck with this problem for a month.
I've been trying to use firebase to create a FIFO Inventory. I am using firebase cloud function to update the FIFO inventory. However if I stress test the following code just 10 times with for loop for both insert (push) and remove (pop), it breaks because of the concurrent update.
Does anyone have another solution for this?
Insert FIFO/PUSH:
let fifoRef = admin.database().ref('fifo/' + item.itemId + '/').push();
let fifo = {
price: data.items[uniqueId].price,
in: data.items[uniqueId].quantity,
quantity: data.items[uniqueId].quantity,
}
fifoRef.set(fifo);
Get FIFO Value/POP (Here I simply update the quantity for POP):
// get fifo
let fifoReference = 'fifo/' + item.itemId;
let fifoRef = admin.database().ref(fifoReference);
fifoRef.once('value').then(currentData => {
let fifo = currentData.val();
for (let key in fifo) {
let val = fifo[key];
if (val.quantity > 0) {
// get fifo quantity
let fifoQuantityRef = admin.database().ref(fifoReference + '/' + key + '/quantity/');
// get local cache value
let fifoQuantityListener = fifoQuantityRef.on('value', () => {
// transaction start
fifoQuantityRef.transaction(function (quantity) {
if (quantity) {
if (quantity > 0 && quantitySubtotal > 0) {
if (quantity >= quantitySubtotal) {
// minus inventory amount
let amount = calculator(quantitySubtotal + "*" + val.price);
quantity = calculator(quantity + "-" + quantitySubtotal);
quantitySubtotal = 0;
// update quantity
return quantity;
} else {
let amount = calculator(quantity + "*" + val.price);
quantitySubtotal = calculator(quantitySubtotal + "-" + quantity);
return 0;
}
}
}
return quantity;
}, (error, committed, result) => {
fifoQuantityRef.off('value', fifoQuantityListener);
}, true);
});
Brainstorming:
I just need Insight on how to get the VALUE using FIFO. From my understanding Firebase is best used to insert and remove not with transaction. But if I am using only insert and remove, how to create a FIFO? If I create FIFO with the quantity of 1, the data stored will be too large.
I did try to use Google Datastore, however datastore persistence is extremely slow (over 2 seconds for writing). Which is not possible to be used with firebase which have persistence of less than 1 second. The problem arise when PUSH and POP is done within 1 seconds, datastore insert is not persisted yet.
Any other brainstorming ideas?
i want to get all the records in particular record type , but i got 1000 only.
This is the code I used.
function getRecords() {
return nlapiSearchRecord('contact', null, null, null);
}
I need two codes.
1) Get whole records at a single time
2) Get the records page wise by passing pageindex as an argument to the getRecords [1st =>0-1000 , 2nd =>1000 - 2000 , ...........]
function getRecords(pageIndex) {
.........
}
Thanks in advance
you can't get whole records at a time. However, you can sort results by internalid, and remember the last internalId of 1st search result and use an additional filter in your next search result.
var totalResults = [];
var res = nlapiSearchRecord('contact', null, null, new nlobjSearchColumn('internalid').setSort()) || [];
lastId = res[res.length - 1].getId();
copyAndPushToArray(totalResult, res);
while(res.length < 1000)
{
res = nlapiSearchRecord('contact', null, ['internalidnumber', 'greaterthan', lastId], new nlobjSearchColumn('internalid').setSort());
copyAndPushToArray(totalResult, res);
lastId = res[res.length - 1].getId();
}
Beware, if the number of records are high you may overuse governance limit in terms of time and usage points.
If you remember the lastId you can write a logic in RESTlet to take id as param and then use that as additional filter to return nextPage.
You can write a logic to get nth pageresult but, you might have to run search uselessly n-1 times.
Also, I would suggest to use nlapiCreateSearch().runSearch() as it can return up to 4000 records
Here is another way to get more than 1000 results on a search:
function getItems() {
var columns = ['internalid', 'itemid', 'salesdescription', 'baseprice', 'lastpurchaseprice', 'upccode', 'quantityonhand', 'vendorcode'];
var searchcolumns = [];
for(var col in columns) {
searchcolumns.push(new nlobjSearchColumn(columns[col]));
}
var search = nlapiCreateSearch('item', null, searchcolumns);
var results = search.runSearch();
var items = [], slice = [], i = 0;
do {
slice = results.getResults(i, i + 1000);
for (var itm in slice) {
var item = {};
for(var col in columns) { item[columns[col]] = slice[itm].getValue(columns[col]); } // convert nlobjSearchResult into simple js object
items.push(item);
i++;
}
} while (slice.length >= 1000);
return items;
}
I am wondering how can I achieve pagination using Cassandra.
Let us say that I have a blog. The blog lists max 10 posts per page. To access next posts a user must click on pagination menu to access page 2 (posts 11-20), page 3 (posts 21-30), etc.
Using SQL under MySQL, I could do the following:
SELECT * FROM posts LIMIT 20,10;
The first parameter of LIMIT is offset from the beginning of result set and second argument is amount of rows to fetch. The example above returns 10 rows starting from row 20.
How can I achieve the same effect in CQL?
I have found some solutions on Google, but all of them require to have "the last result from previous query". It works for having "next" button to paginate to another 10-results-set, but what if I want to jump from page 1 to page 5?
You don't need to use tokens, if you are using Cassandra 2.0+.
Cassandra 2.0 has auto paging.
Instead of using token function to create paging, it is now a built-in feature.
Now developers can iterate over the entire result set, without having to care that it’s size is larger than the memory. As the client code iterates over the results, some extra rows can be fetched, while old ones are dropped.
Looking at this in Java, note that SELECT statement returns all rows, and the number of rows retrieved is set to 100.
I’ve shown a simple statement here, but the same code can be written with a prepared statement, couple with a bound statement. It is possible to disable automatic paging, if it is not desired. It is also important to test various fetch size settings, since you will want to keep the memorize small enough, but not so small that too many round-trips to the database are taken. Check out this blog post to see how paging works server side.
Statement stmt = new SimpleStatement(
"SELECT * FROM raw_weather_data"
+ " WHERE wsid= '725474:99999'"
+ " AND year = 2005 AND month = 6");
stmt.setFetchSize(24);
ResultSet rs = session.execute(stmt);
Iterator<Row> iter = rs.iterator();
while (!rs.isFullyFetched()) {
rs.fetchMoreResults();
Row row = iter.next();
System.out.println(row);
}
Try using the token function in CQL:
https://docs.datastax.com/en/cql-oss/3.3/cql/cql_using/useToken.html
Another suggestion, if you are using DSE, solr supports deep paging:
https://cwiki.apache.org/confluence/display/solr/Pagination+of+Results
Manual Paging
The driver exposes a PagingState object that represents where we were in the result set when the last page was fetched:
ResultSet resultSet = session.execute("your query");
// iterate the result set...
PagingState pagingState = resultSet.getExecutionInfo().getPagingState();
This object can be serialized to a String or a byte array:
String string = pagingState.toString();
byte[] bytes = pagingState.toBytes();
This serialized form can be saved in some form of persistent storage to be reused later. When that value is retrieved later, we can deserialize it and reinject it in a statement:
PagingState pagingState = PagingState.fromString(string);
Statement st = new SimpleStatement("your query");
st.setPagingState(pagingState);
ResultSet rs = session.execute(st);
Note that the paging state can only be reused with the exact same statement (same query string, same parameters). Also, it is an opaque value that is only meant to be collected, stored an re-used. If you try to modify its contents or reuse it with a different statement, the driver will raise an error.
Src: https://docs.datastax.com/en/cql-oss/3.3/cql/cql_reference/cqlshPaging.html
If you read this doc "Use paging state token to get next result",
https://datastax.github.io/php-driver/features/result_paging/
We can use "paging state token" to paginate at application level.
So PHP logic should look like,
<?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']);
}
}
?>
Although the count is available in CQL, so far I have not seen a good solution for the offset part...
So... one solution I have been contemplating was to create sets of pages using a background process.
In some table, I would create the blog page A as a set of references to page 1, 2, ... 10. Then another entry for blog page B pointing to pages 11 to 20, etc.
In other words, I would build my own index with a row key set to the page number. You may still make it somewhat flexible since you can offer the user to choose to see 10, 20 or 30 references per page. For example, when set to 30, you display sets 1, 2, and 3 as page A, sets 4, 5, 6 as page B, etc.)
And if you have a backend process to handle all of that, you can update your lists as new pages are added and old pages are deleted from the blog. The process should be really fast (like 1 min. for 1,000,000 rows if even that slow...) and then you can find the pages to display in your list pretty much instantaneously. (Obviously, if you are to have thousands of users each posting hundreds of pages... that number can grow quickly.)
Where it becomes more complicated is if you wanted to offer a complex WHERE clause. By default a blog shows you a list of all the posts from the newest to the oldest. You could also offer lists of posts with tag Cassandra. Maybe you want to inverse the order, etc. That makes it difficult unless you have some form of advanced way to create your index(es). On my end I have a C-like language which goes and peek and poke to the values in a row to (a) select them and if selected (b) to sort them. In other words, on my end I can already have WHERE clauses as complex as what you'd have in SQL. However, I do not yet break up my lists in pages. Next step I suppose...
Using cassandra-node driver for node js (koa js,marko js) : Pagination
Problem
Due to the absence of skip functionality, we need to work around. Below is the implementation of manual paging for node app in case of anyone can get an idea.
code for simple users list
navigate between next and previous page states
easy to replicate
There are two solutions which i am going to state here but only gave the code for solution 1 below,
Solution 1 : Maintain page states for next and previous records (maintain stack or whatever data structure best fit)
Solution 2 : Loop through all records with limit and save all possible page states in variable and generate pages relatively to their pageStates
Using this commented code in model, we can get all states for pages
//for the next flow
//if (result.nextPage) {
// Retrieve the following pages:
// the same row handler from above will be used
// result.nextPage();
//}
Router Functions
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;
};
Model Functions
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;
};
Html side
<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>
I am not very much experienced with node js and cassandra db, this solution can surely be improved. Solution 1 is working example code to start with the paging idea. Cheers
a detailed blog.
Our use case was similar. Pull everything from a Cassandra table (cassandra does it smartly by fetching ~5000 in one go and return a cursor), heavy personalized processing on each row, and keep going. Once our iteration reaches close to 5000, it again fetches the next chunk of 5000 rows internally and adds it to the result cursor. It does it so brilliantly that we don’t even feel this magic happening behind the scene.
but It became a bottleneck for us.As iterating over the chunk took some time and till it reached the end of the chunk, Cassandra thought the connection was not being used and closed the connection automatically yelling, its timeout. So we implemented with page state.
from cassandra.cluster import Cluster
from cassandra.auth import PlainTextAuthProvider
from cassandra.query import SimpleStatement
# connection with cassandra
cluster = Cluster(["127.0.0.1"], auth_provider=PlainTextAuthProvider(username="pankaj", password="pankaj"))
session = cluster.connect()
# setting keyspace
session.set_keyspace("my_keyspace")
# set fetch size
fetch_size = 100
# It will print first 100 records
next_page_available = True
paging_state = None
data_count = 0
while next_page_available is True:
# fetches a new chunk with given page state
result = fetch_a_fresh_chunk(paging_state)
paging_state = results.paging_state
for result in results:
# process payload here.....
# payload processed
data_count += 1
# once we reach fetch size, we stop cassandra to fetch more chunk, internally
if data_count == fetch_size:
i = 0
break
# fetches a fresh chunk with given page state
def fetch_a_fresh_chunk(paging_state = None)
query = "SELECT * FROM my_cute_cassandra_table;"
statement = SimpleStatement(query, fetch_size = fetch_size)
results = session.execute(statement, paging_state=paging_state)