indexing

问题 Hi I'm trying to implement CoreSpotlight in my app. When indexing do I need to run this every time or is it sufficient to run this once when app is installed for the first time? If app is deleted do I need to index again? Here's the code I'm using: - (void)spotLightIndexing { NSString *path = [[NSBundle mainBundle] pathForResource: @"aDetailed" ofType:@"plist"]; NSDictionary *plistDict = [[NSDictionary alloc] initWithContentsOfFile:path]; NSArray *plistArray = [plistDict allKeys]; for (id key

问题 I am trying to index documents to be searchable on their tag array. CREATE INDEX doc_search_idx ON documents USING gin( to_tsvector('english', array_to_string(tags, ' ')) || to_tsvector('english', coalesce(notes, ''))) ) Where tags is a (ci)text[] . However, PG will refuse to index array_to_string because it is not always immutable. PG::InvalidObjectDefinition: ERROR: functions in index expression must be marked IMMUTABLE I've tried creating a homebrew array_to_string immutable function, but

问题 I have a Solr index with many entries, and upon query some subset is returned - each entry having some score, (Obvious). Once the results are returned with scores, I want to be able to only "keep" results that are above some score (i.e. results of a certain quality only). Is it possible to do this when the returned subset could be anything? I ask because it seems like on some queries a score of say 0.008 is resulting in a decent match, whereas other queries a higher score results in a poor

问题 Is there any reason I shouldn't create an index for every one of my database tables, as a means of increasing performance? It would seem there must be some reason(s) else all tables would automatically have one by default. I use MS SQL Server 2016. 回答1: One index on a table is not a big deal. You automatically have an index on columns (or combinations of columns) that are primary keys or declared as unique. There is some overhead to an index. The index itself occupies space on disk and memory

问题 arr = [1,3,2,4] arr.sort #=> [1,2,3,4] I would like an array [0, 2, 1, 3] (original indexes in arr.sort order) Is there a simple way to do that with Ruby 1.9.3? thank you 回答1: xs = [1, 3, 2, 4] original_indexes = xs.map.with_index.sort.map(&:last) #=> [0, 2, 1, 3] 回答2: arr=[1,3,2,4] p arr.map{|e| arr.sort.index(e)} to avoid sorting each time, better is: arr=[1,3,2,4] arr_s = arr.sort p arr.map{|e| arr_s.index(e)} UPDATED arr=[1,3,2,4] start_time = Time.now (1..100000).each do |i| arr.map{|e|

问题 I want to know how I could perform some kind of index on keys from a python dictionary. The dictionary holds approx. 400,000 items, so I am trying to avoid a linear search. Basically, I am trying to find if the userinput is inside any of the dict keys. for keys in dict: if userinput in keys: DoSomething() break That would be an example of what I am trying to do. Is there a way to search in a more direct way, without a loop ? or what would be a more efficient way. Clarification: The userinput

问题 I'm trying to use a localized index for my UITableView same as iPhone's Contacts application . here is how I return an array of characters: - (NSArray *)sectionIndexTitlesForTableView:(UITableView *)tableView { return [[UILocalizedIndexedCollation currentCollation] sectionIndexTitles]; } I changed the language setting to a non-English (Ex: Russian). However, it always returns an array of character in English: |A|B|C|D|E|F|G|H|I|J|K|L|M|N|O|P|Q|R|S|T|U|V|W|X|Y|Z|# It is unlike the iPhone

问题 Is there a way to systematically select the last columns of a data frame? I would like to be able to move the last columns to be the first columns, but maintain the order of the columns when they are moved. I need a way to do this that does not list all the columns using subset(data, select = c(all the columns listed in the new order)) because I will be using many different data frames. Here's an example where I would like to move the last 2 columns to the front of the data frame. It works,

问题 My question is very similar to this one but I can't manage exactly how to apply that answer to my problem. I am looping through a vector with a variable k and want to select the whole vector except the single value at index k . Any idea? for k = 1:length(vector) newVector = vector( exluding index k); <---- what mask should I use? % other operations to do with the newVector end 回答1: vector([1:k-1 k+1:end]) will do. Depending on the other operations, there may be a better way to handle this,

问题 I am curious as to whether CREATE INDEX idx ON tbl (columns); vs. CREATE UNIQUE INDEX idx ON tbl (columns); has a significant algorithmic performance benefit in PostgreSQL or MySQL implementations when scanning the indexed column(s), or whether the UNIQUE keyword simply introduces a unique constraint alongside the index. I imagine it is probably fair to say that there is a marginal benefit insofar as indexes are likely to be internally implemented as some sort of hash 1 -like structure, and