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Simplify pagination (#689)

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* initial simplification

* simplify forward pagination

* simplifies the backward pagination part

* removes old paginate proc

* revises comments, cleans up the code

* comments on initial paging query

* defines temporary variable for the paginate output
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Sanaz Taheri Boshrooyeh 2021-08-04 15:24:36 -07:00 committed by GitHub
parent 6b1e0c3079
commit 027cd7f95d
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1 changed files with 76 additions and 42 deletions
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waku/v2/protocol/waku_store/waku_store.nim
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@ -283,60 +283,94 @@ proc paginate*(list: seq[IndexedWakuMessage], pinfo: PagingInfo): (seq[IndexedWa
cursor = pinfo.cursor cursor = pinfo.cursor
pageSize = pinfo.pageSize pageSize = pinfo.pageSize
dir = pinfo.direction dir = pinfo.direction
output: (seq[IndexedWakuMessage], PagingInfo, HistoryResponseError)
if pageSize == uint64(0): # pageSize being zero indicates that no pagination is required if pageSize == uint64(0): # pageSize being zero indicates that no pagination is required
return (list, pinfo, HistoryResponseError.NONE) let output = (list, pinfo, HistoryResponseError.NONE)
return output
if list.len == 0: # no pagination is needed for an empty list if list.len == 0: # no pagination is needed for an empty list
return (list, PagingInfo(pageSize: 0, cursor:pinfo.cursor, direction: pinfo.direction), HistoryResponseError.NONE) output = (list, PagingInfo(pageSize: 0, cursor:pinfo.cursor, direction: pinfo.direction), HistoryResponseError.NONE)
return output
var msgList = list # makes a copy of the list
# sorts msgList based on the custom comparison proc indexedWakuMessageComparison
msgList.sort(indexedWakuMessageComparison)
var initQuery = false # adjust pageSize
if cursor == Index(): if pageSize > MaxPageSize:
initQuery = true # an empty cursor means it is an initial query pageSize = MaxPageSize
# sort the existing messages
var
msgList = list # makes a copy of the list
total = uint64(msgList.len)
# sorts msgList based on the custom comparison proc indexedWakuMessageComparison
msgList.sort(indexedWakuMessageComparison)
# set the cursor of the initial paging request
var isInitialQuery = false
if cursor == Index(): # an empty cursor means it is an initial query
isInitialQuery = true
case dir case dir
of PagingDirection.FORWARD: of PagingDirection.FORWARD:
cursor = msgList[0].index # perform paging from the begining of the list cursor = msgList[0].index # set the cursor to the beginning of the list
of PagingDirection.BACKWARD: of PagingDirection.BACKWARD:
cursor = msgList[list.len - 1].index # perform paging from the end of the list cursor = msgList[list.len - 1].index # set the cursor to the end of the list
var foundIndexOption = msgList.findIndex(cursor)
if foundIndexOption.isNone: # the cursor is not valid var cursorIndexOption = msgList.findIndex(cursor)
return (@[], PagingInfo(pageSize: 0, cursor:pinfo.cursor, direction: pinfo.direction), HistoryResponseError.INVALID_CURSOR) if cursorIndexOption.isNone: # the cursor is not valid
var foundIndex = uint64(foundIndexOption.get()) output = (@[], PagingInfo(pageSize: 0, cursor:pinfo.cursor, direction: pinfo.direction), HistoryResponseError.INVALID_CURSOR)
var retrievedPageSize, s, e: uint64 return output
var newCursor: Index # to be returned as part of the new paging info var cursorIndex = uint64(cursorIndexOption.get())
case dir case dir
of PagingDirection.FORWARD: # forward pagination of PagingDirection.FORWARD: # forward pagination
# the message that is pointed by the cursor is excluded for the retrieved list, this is because this message has already been retrieved by the querier in its prior request # set the index of the first message in the page
var remainingMessages= uint64(msgList.len) - uint64(foundIndex) - 1 # exclude the message pointing by the cursor
if initQuery: remainingMessages = remainingMessages + 1 var startIndex = cursorIndex + 1
# the number of queried messages cannot exceed the MaxPageSize and the total remaining messages i.e., msgList.len-foundIndex # for the initial query, include the message pointing by the cursor
retrievedPageSize = min(uint64(pageSize), MaxPageSize).min(remainingMessages) if isInitialQuery:
if initQuery : foundIndex = foundIndex - 1 startIndex = cursorIndex
s = foundIndex + 1 # non inclusive
e = foundIndex + retrievedPageSize # adjust the pageSize based on the total remaining messages
newCursor = msgList[e].index # the new cursor points to the end of the page pageSize = min(pageSize, total - startIndex)
of PagingDirection.BACKWARD: # backward pagination
var remainingMessages = foundIndex
if initQuery: remainingMessages = remainingMessages + 1
# the number of queried messages cannot exceed the MaxPageSize and the total remaining messages i.e., foundIndex-0
retrievedPageSize = min(uint64(pageSize), MaxPageSize).min(remainingMessages)
if initQuery : foundIndex = foundIndex + 1
s = foundIndex - retrievedPageSize
e = foundIndex - 1
newCursor = msgList[s].index # the new cursor points to the begining of the page
if (retrievedPageSize == 0): if (pageSize == 0):
return (@[], PagingInfo(pageSize: 0, cursor:pinfo.cursor, direction: pinfo.direction), HistoryResponseError.NONE) output = (@[], PagingInfo(pageSize: pageSize, cursor:pinfo.cursor, direction: pinfo.direction), HistoryResponseError.NONE)
return output
# set the index of the last message in the page
var endIndex = startIndex + pageSize - 1
# retrieve the messages
var retMessages: seq[IndexedWakuMessage]
for i in startIndex..endIndex:
retMessages.add(msgList[i])
output = (retMessages, PagingInfo(pageSize : pageSize, cursor : msgList[endIndex].index, direction : pinfo.direction), HistoryResponseError.NONE)
return output
of PagingDirection.BACKWARD:
# set the index of the last message in the page
# exclude the message pointing by the cursor
var endIndex = cursorIndex - 1
# for the initial query, include the message pointing by the cursor
if isInitialQuery:
endIndex = cursorIndex
# adjust the pageSize based on the total remaining messages
pageSize = min(pageSize, endIndex + 1)
if (pageSize == 0):
output = (@[], PagingInfo(pageSize: pageSize, cursor:pinfo.cursor, direction: pinfo.direction), HistoryResponseError.NONE)
return output
# set the index of the first message in the page
var startIndex = endIndex - pageSize + 1
# retrieve the messages
var retMessages: seq[IndexedWakuMessage]
for i in startIndex..endIndex:
retMessages.add(msgList[i])
output = (retMessages, PagingInfo(pageSize : pageSize, cursor : msgList[startIndex].index, direction : pinfo.direction), HistoryResponseError.NONE)
return output
# retrieve the messages
var retMessages: seq[IndexedWakuMessage]= @[]
for i in s..e:
retMessages.add(msgList[i])
return (retMessages, PagingInfo(pageSize : retrievedPageSize, cursor : newCursor, direction : pinfo.direction), HistoryResponseError.NONE)
proc findMessages(w: WakuStore, query: HistoryQuery): HistoryResponse = proc findMessages(w: WakuStore, query: HistoryQuery): HistoryResponse =
var data : seq[IndexedWakuMessage] = w.messages var data : seq[IndexedWakuMessage] = w.messages