Query Language
This module is capable of working with both SQL and NoSQL databases, through Sequelize and Mongoose respectively.
These ORMs were chosen due to their similar functions and architectures, allowing for the creation of a very consistent API.
In order to maintain a compatibility layer between the two ORMS, certain operations may not be supported.
New features are being added on-demand and when they can be adapted to both systems.
The query language used is BSON, since it is easy to serialize into string and deserialize back into
query objects that can be easily manipulated in JS.
This means that the database module will almost always have better support for Mongo operations than SQL ones,
since the latter need to go through parsers that are otherwise unnecessary for Mongo.
Supported Operators
| Operator | Description |
|---|---|
| in | Matches any of the values specified in an array |
| contains | Checks if a value is contained in an array or not. |
| nin | Selects the documents where the value of a field is not equal any value in the specified array. |
| eq | Matches documents where the value of a field equals the specified value. |
| ne | Selects the documents where the value of the field is not equal to the specified value |
| lt | Selects the documents where the value of the field is less than (i.e. <) the specified value. |
| gt | Selects the documents where the value of the field is greater than (i.e. >) the specified value. |
| lte | Selects the documents where the value of the field is less or equal than (i.e. <=) the specified value. |
| gte | Selects the documents where the value of the field is greater or equal than (i.e. >=) the specified value. |
| or | Performs OR operation on an array of two or more expressions and selects the documents that satisfy at least one |
| and | Performs AND operation on an array of two or more expressions and selects the documents that satisfy at least one |
| not | Performs NOT operation on an array of two or more expressions and selects the documents that do not match the expression |
| regex | Select the documents where the value of the field matches the regex. |
These operators have been tested thoroughly in varying levels of complexity
Populations & Relations
Relations have been implemented with MongoDB in mind.
This means that they do not really exist inside the databases (for now).
Every relation is logical, and relation data is retrieved using Mongoose's population functionality.
The same reasoning has been carried over to Sequelize, but is not currently as efficient.
Getting related fields
Each relation field can be filled (or populated) by supplying a relevant array, creating a join operation that gets all the objects.
Setting related fields
While we advise creating each document seperately and setting the relation inside a model after the "child" document has been created, the database module supports "create with population" operations, where if you supply an entire object instead of an id in the place of the relation field, then the module will automatically create the associated document and add its id in place of the data.
Sequelize Caveats
Currently the Sequelize implementation has the following limitations:
- No index creation
- Update queries only update provided fields without the option to replace entire rows, unless all columns are provided.
- Like operations do not work