indexing

问题 The latest version of MongoDB (v3.2) adds support for partial (filtered) indexes. You supply a filter when you create the index and that filter determines which documents will be referenced in the index and which will not. Can I use any filter expression (as long as it's a valid filter)? Or are there limitations to the filter being used? If so, what are those limitations? 回答1: Can I use any filter expression? No, partial indexes support only a subset of the operators in the filter used. The

问题 The latest version of MongoDB (v3.2) adds support for partial (filtered) indexes. You supply a filter when you create the index and that filter determines which documents will be referenced in the index and which will not. Can I use any filter expression (as long as it's a valid filter)? Or are there limitations to the filter being used? If so, what are those limitations? 回答1: Can I use any filter expression? No, partial indexes support only a subset of the operators in the filter used. The

问题 The latest version of MongoDB (v3.2) adds support for partial (filtered) indexes. You supply a filter when you create the index and that filter determines which documents will be referenced in the index and which will not. Can I use any filter expression (as long as it's a valid filter)? Or are there limitations to the filter being used? If so, what are those limitations? 回答1: Can I use any filter expression? No, partial indexes support only a subset of the operators in the filter used. The

问题 I have a pandas dataFrame called 'df' as follows value 2015-09-27 03:58:30 1.0 2015-09-27 03:59:30 1.0 2015-09-27 04:00:30 1.0 2015-09-27 04:01:30 1.0 I just want to strip out the seconds to get this value 2015-09-27 03:58:00 1.0 2015-09-27 03:59:00 1.0 2015-09-27 04:00:00 1.0 2015-09-27 04:01:00 1.0 How can i do this? ive tried things like df.index.to_series().apply(datetime.replace(second=0, microsecond=0)) but i always get errors TypeError: descriptor 'replace' of 'datetime.datetime'

问题 I have always tried to have an integer primary key on a table no matter what. But now I am questioning if this is always necessary. Let's say I have a product table and each product has a globally unique SKU number - that would be a string of say 8-16 characters. Why not make this the PK? Typically I would make this field a unique index but then have an auto incrementing int field as the PK, as I assumed it would be faster, easier to maintain, and would allow me to do things like get the last

问题 I have always tried to have an integer primary key on a table no matter what. But now I am questioning if this is always necessary. Let's say I have a product table and each product has a globally unique SKU number - that would be a string of say 8-16 characters. Why not make this the PK? Typically I would make this field a unique index but then have an auto incrementing int field as the PK, as I assumed it would be faster, easier to maintain, and would allow me to do things like get the last

问题 I wanted to ask if there is some kind of utility function which offers array joining while providing an index. Maybe Prototype of jQuery provides this, if not, I will write it on my own :) What I expect is something like var array= ["a", "b", "c", "d"]; function Array.prototype.join(seperator [, startIndex, endIndex]){ // code } so that array.join("-", 1, 2) would return "b-c" Is there this kind of utility function in an pretty common Javascript Library? Regards Wormi 回答1: It works native ["a

问题 This question already has answers here : Index of max and min value in an array (3 answers) Closed 5 years ago . I'm trying to find the maximum value of a certain column in a matrix. I want to find both the maximum value and the index of the row in which it is. How can I do this? 回答1: max command can find both the maximal value and its index. Here's an example: >> A = randn(10,3) A = 0.8884 -0.10224 -0.86365 -1.1471 -0.24145 0.077359 -1.0689 0.31921 -1.2141 -0.8095 0.31286 -1.1135 -2.9443 -0

问题 For instance, my query is like the following using SQL Server 2005: SELECT * FROM Table WHERE FREETEXT(SearchField, 'c#') I have a full text index defined to use the column SearchField which returns results when using: SELECT * FROM Table WHERE SearchField LIKE '%c#%' I believe # is a special letter, so how do I allow FREETEXT to work correctly for the query above? 回答1: The # char is indexed as punctuation and therefore ignored, so it looks like we'll remove the letter C from our word

问题 I am working on a custom data structure and I am currently in the beta testing process: The data will be stored within an array and this array can be represented as a 4D, 2D & 1D array. These three arrays are declared within a union since it represents the same memory addressing. Here is the declaration to my class: SomeClass.h #ifndef SomeClass_H #define SomeClass_H class SomeClass { public: static const unsigned V1D_SIZE; // Single Or Linear Array Representation : Size 256 - 256 Elements