indexing

问题 I have structure like this: user_id, a. a is of type jsonb and has the following structure: { b: [ {ids: [1,2,3,4]}, {ids: [2,3,4]}, {ids: [1,2,4]}, ... ] } How would I make an index that enabled me to find all users (user_id) that has a certain id in the ids list? 回答1: Is a GIN index what you want? It seems that you first need to organized the IDs into a form that is more tractable. I'm more familiar with Python than I am with the PostgreSQL ways of manipulating JSON, so I used PL/Python for

问题 So I am using Algolia.com to index users for quick searching. An example object in index: { id: 1, username: "john.doe", name: "John Doe", attributes: { gender: "male", hair_color: "blonde", eye_color: "blue", height: 165 } } I'd like to filter results by a specific attribute (object key) in the attributes object. I thought maybe using facetFilters would do the job, but I am unable to get it working. I have tried many variances of this code: user_index.search('', { facets: '*', facetFilters:

问题 I know Spark Sql is almost same as Hive. Now I have created a table and when I am doing Spark sql query to create the table index, it always gives me this error: Error in SQL statement: AnalysisException: mismatched input '' expecting AS near ')' in create index statement The Spark sql query I am using is: CREATE INDEX word_idx ON TABLE t (id) The data type of id is bigint. Before this, I have also tried to create table index on "word" column of this table, it gave me the same error. So, is

问题 I need to search over a DB table using some kind of fuzzy search like the one from oracle and using indexes since I do not want a table scan(there is a lot of data). I want to ignore case, language special stuff(ñ, ß, ...) and special characters like _, (), -, etc... Search for "maria (cool)" should get "maria- COOL" and "María_Cool" as matches. Is that possible in Oracle in some way? About the case, I think it can be solved created the index directly in lower case and searching always lower

问题 I stumbled upon code containing something like: char c = "abc"[1]; and it compiles and runs fine with gcc! c will be 'b' after this expression. Is this standard to index literal strings or is it mere luck that it works? 回答1: Of course it is, a string literal is of array type. It is converted to a pointer to char in the expression and is like an any pointer to char . char c = "abc"[1]; and char *p = "abc"; char c = p[1]; are equivalent. 回答2: This is entirely standard. A string is actually a

问题 I have a MongoDB-based database with something about 100K to 500K text documents inside and the collection keeps growing. The system should support the queries by different fields of the documents, e.g. title, category, importance etc. The system is a near real-time system, which got new documents every 5-10 minutes. My question: Is it a good idea, in order to boost the queries' performance, to define a separate index for each frequently queried field (field types: small text, numeric, date)

问题 I want to split a list into chunks using values of of another list as the range to split. indices = [3, 5, 9, 13, 18] my_list = ['a', 'b', 'c', ..., 'x', 'y', 'z'] So basically, split my_list from range: my_list[:3], mylist[3:5], my_list[5:9], my_list[9:13], my_list[13:18], my_list[18:] I have tried to indices into chunks of 2 but the result is not what i need. [indices[i:i + 2] for i in range(0, len(indices), 2)] My actual list length is 1000. 回答1: You could also do it using simple python.

问题 According to the documentation on the createIndexes command: If you create an index with one set of options and then issue createIndexes with the same index fields but different options, MongoDB will not change the options nor rebuild the index. The solution is to drop the index and create it from scratch, but that's costly. Is there a way to create an index when there isn't one, do nothing if there is an index with the same options, and replace the index if the options have changed? This

问题 I'm storing a Document which has a URL field: Document doc = new Document(); doc.add(new Field("url", url, Field.Store.YES, Field.Index.NOT_ANALYZED)); doc.add(new Field("text", text, Field.Store.YES, Field.Index.ANALYZED)); doc.add(new Field("html", CompressionTools.compressString(html), Field.Store.YES)); I'd like to be able to find a Document by its URL, but I get 0 results: Analyzer analyzer = new StandardAnalyzer(Version.LUCENE_30) Query query = new QueryParser(LUCENE_VERSION, "url",

问题 Is it possible in Matlab to use only matrix operations in order to create a NxN matrix Mat like the following two foor loops would do? Mat = zeros(N); for row = 1:N for col = 1:N if (row == 1 && (1 <= col && col <= N)) Mat(row,col) = N; end if ((2 <= row && row <= N) && (1 <= col && col <= N)) Mat(row,col) = (2*row+1)*col; end end end I thought indexing the corresponding rows and columns like: Mat(1,1:N) = N; row = 2:N; col = 1:N; Mat(row,col) = (2.*row+1).*col; The first line is working. But