indexing

问题 I have a simple table with about 3 million records. I made the neccessary indexes, i also force the index PRIMARY but still doesnt work. It searches for nearly all 3 million rows instead of using the index to execute this one (record_id is INT auto-increment): EXPLAIN SELECT record_id FROM myrecords FORCE INDEX ( PRIMARY ) ORDER BY record_id ASC LIMIT 2955900 , 300 id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE myrecords index NULL PRIMARY 4 NULL 2956200 Using

问题 The problem here I am trying to solve is I have a bunch of documents which context mathematical expressions/formulas. I want to search the documents by the formula or expression. So far based on my research I'm considering to convert the mathematical expression to latex format and store as a string in the database (elastic search). With this approach will be I able to search for documents with the latex string? Example latex conversion of a2 + b2 = c2 is a^{2} + b^{2} = c^{2} . Can this

问题 This question already has answers here : PostgreSQL: Index the day part of a timestamp (2 answers) Closed 4 years ago . I am creating a summary table that sums up all events in a given day. INSERT INTO graph_6( day, event_type, (SELECT COUNT(*) FROM event e WHERE event_type = e.event_type AND creation_time::DATE = sq.day) FROM event_type CROSS JOIN (SELECT generate_series( (SELECT '2014-01-01'::DATE), (SELECT '2014-01-02'::DATE), '1 day') as day) sq; The creation_time column is indexed:

问题 This question already has answers here : Getting the last element of a list (11 answers) Closed 3 years ago . I am able to get the second-to-last element of a list with the following: >>> lst = ['a', 'b', 'c', 'd', 'e', 'f'] >>> print(lst[len(lst)-2]) e Is there a better way than using print(lst[len(lst)-2]) to achieve this same result? 回答1: There is: negative indices: lst[-2] 来源： https://stackoverflow.com/questions/39838900/getting-second-to-last-element-in-list

问题 This question already has answers here : Getting the last element of a list (11 answers) Closed 3 years ago . I am able to get the second-to-last element of a list with the following: >>> lst = ['a', 'b', 'c', 'd', 'e', 'f'] >>> print(lst[len(lst)-2]) e Is there a better way than using print(lst[len(lst)-2]) to achieve this same result? 回答1: There is: negative indices: lst[-2] 来源： https://stackoverflow.com/questions/39838900/getting-second-to-last-element-in-list

问题 Is it possible to update some specific fields value in elasticsearch with out overwriting other fields. ? 回答1: As a codebased contribution to this answer, the following query may be used: POST /index/type/100100471/_update { "doc" : { "yourProperty" : 10000 } } This query updates yourProperty property only . As a result, this response appears: { "_index": "index", "_type": "type", "_id": "100100471", "_version": 1, "_shards": { "total": 0, "successful": 1, "failed": 0 } } 回答2: Yes,

问题 I am making a collection of user's data. This will be pretty basic consisting of user's email, user's password (hashed), and an array of strings. { email: 'user@example.com', password: 'password hash', arr: [] } I want to make sure that there can't be two inserts with the same email . I read that the _id of mongoDB is unique by default, and it uses some special data structure for improved performance. How can I make sure that the email remains unique, and if possible can I leverage the

问题 Say I have a list of object Person { public string Name {get; set;} public string Gender {get; set;} } What I want is to create a List that I can order by using a property called OrderIndex. So I add this property to the Person object: { public string Name {get; set;} public string Gender {get; set;} public int OrderIndex {get; set;} } The purpose of this OrderIndex property is to place the Person object in the list at a specific index for ranking the Person object higher. But I am very

问题 Say I have a list of object Person { public string Name {get; set;} public string Gender {get; set;} } What I want is to create a List that I can order by using a property called OrderIndex. So I add this property to the Person object: { public string Name {get; set;} public string Gender {get; set;} public int OrderIndex {get; set;} } The purpose of this OrderIndex property is to place the Person object in the list at a specific index for ranking the Person object higher. But I am very

问题 Can Apache Solr be used to index all the files of a folder(Parent) and its subfolders, containing files of all types: XML, .json, .pdf,.doc etc..? 回答1: Using post tool can be done java -Dc=test -Drecursive -Dauto -jar post.jar folder -Dauto for all file types that solr can handle -Dc to specify collection name -Drecursive to handle if folder has files inside subfolder. if folder has has subfolder it will index files inside subfolder 回答2: You need to use a Data Import Handler to achieve that .