Does Firebird have an addition assignment (+=) to be used in procedures?
No, Firebird doesn't have compound assignment operators.
Related
I need to write a query that use any of the different tag I define, because the historian database supports only this type of where condition.
{tag="pressure" OR tag="level" OR tag="prometheus"} Is it possible to write logical binary operators?
I don´t know how to resolve this.
Which one is good mongodb aggregate or mongodb functions
what i mean to say : mongodb aggregation or mongodb functional which one is preforable and which one gives good performance.
Mongodb functions
Defines a custom aggregation function or expression in JavaScript.
Whereas aggregation is a prebuilt supported operations.
Executing JavaScript inside an aggregation expression may decrease performance. Only use the $function operator if the provided pipeline operators cannot fulfill your application's needs.
If you have a logic which needs to be customised not supported out of the box, go for functions.
Reference
I'm setting up a python application which uses mongodb (through pymongo).
I need to overwrite the contents of an entire document. This can be done either with update or replace. However, the mongo documentation isn't explicit about the atomicity of these operations - saying only that individual write operations are atomic, without explaining if update or replace use multiple write operations.
Does anyone know for sure if either of these operations is completely atomic?
find_and_modify is deprecated in the pymongo driver. Instead use one of:
find_one_and_delete
find_one_and_replace
find_one_and_update
The original find_and_modify had the potential to modify multiple documents which is probably not what was intended and is also not atomic.
For a truly ACID compiant sequence of modifications in MongoDB please look at MongoDB ACID Transactions. Supported since MongoDB 4.0, released last year.
Mongodb's dot notation feature is quite cool, but I find that it seems not work on referred documents.
So dot notation can only be used in embedded arrays or subdocuments, am I right?
Thank you.
Dot notation may only be used to query within the fields of a single document (or sub-document). It cannot be used to refer/query on other documents.
While there are times where I thought it would be an interesting feature to add, it's generally easy to create an alternative schema design that doesn't require it for "queryability" or performance.
I have a Postgres database that has 2 columns that are not primary keys (nor can be), but are searched on a lot and are compared for equality to 2 columns in other tables.
I believe this is a perfect case for adding an index to my tables. I have never used indexing on a database before so I am trying to learn the proper way of doing this.
I have learned that there are multiple types of indexing I can pick from. How do I determine what method will be the most efficient for my database? Also would the proper method be to create a single index that covers both columns?
Postgres support B-tree, R-tree, Hash, GiST and GIN indexing types. B-tree indexing is the most common and fits most common scenarios. This is the syntax:
CREATE INDEX idex_name ON table_name USING btree(column1, column2);
Here is the createindex documentation and here is more info on different indextypes in postgres.
What type of index you should use depends on what types of operations you want to perform. If you simply want equality checking then hash index is the best. For most common operations(e.g. comparison, pattern matching) B-tree should be used. I have personally never used GiST or GIN indexing. ANY Guru out there?
The documentation describes all these types. They can help you better than me :)
Hope this helps.
Try to understand the queryplanner as well, because this part of PostgreSQL has to work with your indexes. EXPLAIN ANALYZE will be essential to optimise your queries.