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Searching: More docs and a bit of simplification.

pull/21833/head
Damir Jelić 2020-06-04 16:57:28 +02:00
parent bf13032d5b
commit 5dfe5ac135
1 changed files with 127 additions and 7 deletions
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134
src/Searching.js
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@ -204,7 +204,9 @@ function compareOldestEvents(firstResults, secondResults) {
}
function combineEventSources(previousSearchResult, response, a, b) {
// Merge event sources and sort the events.
const combinedEvents = a.concat(b).sort(compareEvents);
// Put half of the events in the response, and cache the other half.
response.results = combinedEvents.slice(0, SEARCH_LIMIT);
previousSearchResult.cachedEvents = combinedEvents.slice(SEARCH_LIMIT);
}
@ -212,13 +214,104 @@ function combineEventSources(previousSearchResult, response, a, b) {
/**
* Combine the events from our event sources into a sorted result
*
* This method will first be called from the combinedSearch() method. In this
* case we will fetch SEARCH_LIMIT events from the server and the local index.
*
* The method will put the SEARCH_LIMIT newest events from the server and the
* local index in the results part of the response, the rest will be put in the
* cachedEvents field of the previousSearchResult (in this case an empty search
* result).
*
* Every subsequent call will be made from the combinedPagination() method, in
* this case we will combine the cachedEvents and the next SEARCH_LIMIT events
* from either the server or the local index.
*
* Since we have two event sources and we need to sort the results by date we
* need keep on looking for the oldest event. We are implementing a variation of
* a sliding window.
*
* If we set SEARCH_LIMIT to 3:
*
* Server events [01, 02, 04, 06, 07, 08, 11, 13]
* |01, 02, 04|
* Local events [03, 05, 09, 10, 12, 14, 15, 16]
* |03, 05, 09|
*
* We note that the oldest event is from the local index, and we combine the
* results:
*
* Server window [01, 02, 04]
* Local window [03, 05, 09]
*
* Combined events [01, 02, 03, 04, 05, 09]
*
* We split the combined result in the part that we want to present and a part
* that will be cached.
*
* Presented events [01, 02, 03]
* Cached events [04, 05, 09]
*
* We slide the window for the server since the oldest event is from the local
* index.
*
* Server events [01, 02, 04, 06, 07, 08, 11, 13]
* |06, 07, 08|
* Local events [03, 05, 09, 10, 12, 14, 15, 16]
* |XX, XX, XX|
* Cached events [04, 05, 09]
*
* We note that the oldest event is from the server and we combine the new
* server events with the cached ones.
*
* Cached events [04, 05, 09]
* Server events [06, 07, 08]
*
* Combined events [04, 05, 06, 07, 08, 09]
*
* We split again.
*
* Presented events [04, 05, 06]
* Cached events [07, 08, 09]
*
* We slide the local window, the oldest event is on the server.
*
* Server events [01, 02, 04, 06, 07, 08, 11, 13]
* |XX, XX, XX|
* Local events [03, 05, 09, 10, 12, 14, 15, 16]
* |10, 12, 14|
*
* Cached events [07, 08, 09]
* Local events [10, 12, 14]
* Combined events [07, 08, 09, 10, 12, 14]
*
* Presented events [07, 08, 09]
* Cached events [10, 12, 14]
*
* Next up we slide the server window again.
*
* Server events [01, 02, 04, 06, 07, 08, 11, 13]
* |11, 13|
* Local events [03, 05, 09, 10, 12, 14, 15, 16]
* |XX, XX, XX|
*
* Cached events [10, 12, 14]
* Server events [11, 13]
* Combined events [10, 11, 12, 13, 14]
*
* Presented events [10, 11, 12]
* Cached events [13, 14]
*
* We have one source exhausted, we fetch the rest of our events from the other
* source and combine it with our cached events.
*
*
* @param {object} previousSearchResult A search result from a previous search
* call.
* @param {object} localEvents An unprocessed search result from the event
* index.
* @param {object} serverEvents An unprocessed search result from the server.
*
* @ return {object} A response object that combines the events from the
* @return {object} A response object that combines the events from the
* different event sources.
*
*/
@ -230,6 +323,9 @@ function combineEvents(previousSearchResult, localEvents = undefined, serverEven
response.highlights = previousSearchResult.highlights;
if (localEvents && serverEvents) {
// This is a first search call, combine the events from the server and
// the local index. Note where our oldest event came from, we shall
// fetch the next batch of events from the other source.
if (compareOldestEvents(localEvents, serverEvents) < 0) {
oldestEventFrom = "local";
}
@ -237,18 +333,28 @@ function combineEvents(previousSearchResult, localEvents = undefined, serverEven
combineEventSources(previousSearchResult, response, localEvents.results, serverEvents.results);
response.highlights = localEvents.highlights.concat(serverEvents.highlights);
} else if (localEvents) {
// This is a pagination call fetching more events from the local index,
// meaning that our oldest event was on the server.
// Change the source of the oldest event if our local event is older
// than the cached one.
if (compareOldestEvents(localEvents, cachedEvents) < 0) {
oldestEventFrom = "local";
}
combineEventSources(previousSearchResult, response, localEvents.results, cachedEvents);
} else if (serverEvents) {
// This is a pagination call fetching more events from the server,
// meaning that our oldest event was in the local index.
// Change the source of the oldest event if our server event is older
// than the cached one.
if (compareOldestEvents(serverEvents, cachedEvents) < 0) {
oldestEventFrom = "server";
}
combineEventSources(previousSearchResult, response, serverEvents.results, cachedEvents);
} else {
// This is a pagination call where we exhausted both of our event
// sources, let's push the remaining cached events.
response.results = cachedEvents;
delete previousSearchResult.cachedEvents;
previousSearchResult.cachedEvents = [];
}
previousSearchResult.oldestEventFrom = oldestEventFrom;
@ -258,8 +364,18 @@ function combineEvents(previousSearchResult, localEvents = undefined, serverEven
/**
* Combine the local and server search responses
*
* @param {object} previousSearchResult A search result from a previous search
* call.
* @param {object} localEvents An unprocessed search result from the event
* index.
* @param {object} serverEvents An unprocessed search result from the server.
*
* @return {object} A response object that combines the events from the
* different event sources.
*/
function combineResponses(previousSearchResult, localEvents = undefined, serverEvents = undefined) {
// Combine our events first.
const response = combineEvents(previousSearchResult, localEvents, serverEvents);
// Our first search will contain counts from both sources, subsequent
@ -293,7 +409,7 @@ function combineResponses(previousSearchResult, localEvents = undefined, serverE
// pagination request.
//
// Provide a fake next batch token for that case.
if (!response.next_batch && previousSearchResult.cachedEvents && previousSearchResult.cachedEvents.length > 0) {
if (!response.next_batch && previousSearchResult.cachedEvents.length > 0) {
response.next_batch = "cached";
}
@ -310,13 +426,15 @@ async function combinedPagination(searchResult) {
let localResult;
let serverSideResult;
if ((searchArgs.next_batch && oldestEventFrom === "server") ||
(!searchResult.serverSideNextBatch && searchArgs.next_batch)) {
// Fetch events from the local index if we have a token for itand if it's
// the local indexes turn or the server has exhausted its results.
if (searchArgs.next_batch && (!searchResult.serverSideNextBatch || oldestEventFrom === "server")) {
localResult = await eventIndex.search(searchArgs);
}
if ((searchResult.serverSideNextBatch && oldestEventFrom === "local") ||
(!searchArgs.next_batch && searchResult.serverSideNextBatch)) {
// Fetch events from the server if we have a token for it and if it's the
// local indexes turn or the local index has exhausted its results.
if (searchResult.serverSideNextBatch && (oldestEventFrom === "local" || !searchArgs.next_batch)) {
const body = {body: searchResult._query, next_batch: searchResult.serverSideNextBatch};
serverSideResult = await client.search(body);
}
@ -327,6 +445,7 @@ async function combinedPagination(searchResult) {
serverEvents = serverSideResult.search_categories.room_events;
}
// Combine our events.
const combinedResult = combineResponses(searchResult, localResult, serverEvents);
const response = {
@ -335,6 +454,7 @@ async function combinedPagination(searchResult) {
},
};
// Let the client process the combined result.
const result = client._processRoomEventsSearch(searchResult, response);
searchResult.pendingRequest = null;