dy-sql 1.0.2

Dynamically runs SQL queries and executions.

This project consists of a set of python decorators that eases integration with SQL databases. These decorators may trigger queries, inserts, updates, and deletes.

The decorators are a way to help us map our data in python to SQL queries and vice versa. When we select, insert, update, or delete the queries, we pass the data we want to insert along with a well defined query.

This is designed to be done with minimal setup and coding. You need to specify the database connection parameters and annotate any SQL queries/updates you have with the decorator that fits your needs.

Component Breakdown

• set_database_parameters - this function needs to be used to set the database parameters so when a decorator function is called, it can initialize a connection pool to a correct database.

• DbMapResult - this is a base class that can be used when selecting out data that helps to map the results of a query to an object in python

• @sqlquery - this is a decorator for select queries that can return a sql result in a DbMapResult

• @sqlinsert - this is a decorator for any queries that can change data in the database. This can take a set of values and yield multiple operations back for insertions inside of a transaction.

• @sqlexists - this is a decorator that does a select query but wraps it and handles the return values giving back a True or False

Database Preperation

In order to initialize a connection pool when you first call a function with a sql decorator, the database needs to be set up. this is an init function to help with this. in your initialization code for your app, call the init function like in the following example.

from dysql import set_database_parameters


def set_database_from_config():
    maria_db_config = {...}
    set_database_parameters(
        maria_db_host,
        maria_db_user,
        maria_db_password,
        maria_db_databas,
        port=maria_db_port,
    )

Note: the keyword arguments are not required and have standard default values, the port for example defaults to 3306

Decorators

Decorators are an easy way for us to tell a function to be a ‘query’ and return

a result without having to have a big chunk of boiler plate code. once the database has been prepared, calling a sql decorated function will initialize the database, parse the value returned in your function, make a corresponding parameterized query and return the results.

The basic structure is to decorate a method that returns a query string and its

parameters should it have any parameters. There are multiple options for returning a query. below is a summary of some of the possibilities:

• return a QueryData object that possibly contains queryparams and or templateparams

• yield one or more QueryData object that possibly contains queryparams and or templateparams

DbMapResult

This wraps and returns the results of a query making it easier to access the data you put into it for example if you make the query “SELECT id, name FROM table”, it would return a list of DbMapResult objects that contain fields for each of those properties. You could then easily loop through and access the properties like in the following example

@sqlquery()
def get_items_from_sql_query():
    return QueryData("SELECT id, name FROM table")

def get_and_process_items():
    for item in get_items_from_sql_query():
        # we are able to access properties on the object
        print('{name} goes with {id}'.format(item.name, item.id))

We can inherit from DbMapResult and override the way our data maps into the object. This is primarily helpful in cases where we end up with multiple rows because a query has a 1 to many relationship

class ExampleMap(DbMapResult):
    def map_result(self, result):
        # we know we are mapping multiple rows to a single result
        if self.id is None:
            #in our case we know the id is the same so we only set it the first time
            self.id = result['id']
            #initialize our array
            self.item_names = []

    #we know that every result for a given id has a unique item_name
    self.item_names.append(result['item_name'])

@sqlquery(mapping=ExampleMap)
def get_table_items()
    return QueryData("""
        SELECT id, name, item_name FROM table
        JOIN table_item ON table.id = table_item.table_id
        JOIN item ON item.id = table_item.item_id""")

def print_item_names()
    for table_item in get_table_items():
        for item_name in table_item.item_names:
            print('table name {} has item {}'.format(table_item.name, item_name))

@sqlquery

This is for making sql select calls. An optional mapper may be specified to change the behavior of what is returned from a decorated method. The default mapper can combine multiple records into a single result if there is an id field present in each record. Mappers available:

• RecordCombiningMapper (default) - returns a list of results, with multiple records with the same id value being combined into a single result. An optional record_mapper value may be passed to the constructor to change how records are mapped to result.

• SingleRowMapper - returns an object for the first record from the database (even if multiple records are returned). An optional record_mapper value may be passed to the construct to change how this first record is mapped to the result.

• SingleColumnMapper - returns a list of scalars with the first column from every record, even if multiple columns are returned from the database.

• SingleRowAndColumnMapper - returns a single scalar value even if multiple records and columns are returned from the database.

• CountMapper - alias for SingleRowAndColumnMapper to make it clearer for counting queries.

• Custom mappers may be made by extending the BaseMapper class and implementing the map_records method.

basic query with conditions hardcoded into query and default mapper

def get_items():
    items = select_items_for_joe()
    # ... work on items

@sqlquery()
def select_items_for_joe()
    return QueryData("SELECT * FROM table WHERE name='joe'")

basic query with params passed as a dict

def get_items():
    items = select_items_for_name('joe')
    # ... work on items, which contains all records matching the name

@sqlquery()
def select_items_for_name(name)
    return QueryData("SELECT * FROM table WHERE name=:name", query_params={'name':name})

query that only returns a single result from the first row

def get_joe_id():
    result = get_item_for_name('joe')
    return result.get('id')

# Either an instance or class may be used as the mapper parameter
@sqlquery(mapper=SingleRowMapper())
def get_item_for_name(name)
    return QueryData("SELECT id, name FROM table WHERE name=:name", query_params={'name':name})

alternative to the above query that returns the id directly

def get_joe_id():
    return get_id_for_name('joe')

@sqlquery(mapper=SingleRowAndColumnMapper)
def get_id_for_name(name)
    return QueryData("SELECT id FROM table WHERE name=:name", query_params={'name':name})

query that returns a list of scalar values containing the list of distinct names available

def get_unique_names():
    return get_names_from_items()

@sqlquery(mapper=SingleColumnMapper)
def get_names_from_items()
    return QueryData("SELECT DISTINCT(name) FROM table")

basic count query that only returns the scalar value returned for the count

def get_count_for_joe():
    return get_count_for_name('joe')

@sqlquery(mapper=CountMapper)
def get_count_for_name(name)
    return QueryData("SELECT COUNT(*) FROM table WHERE name=:name", query_params={'name':name})

@sqlupdate

Handles anything that is not a select. this is primarily, but not limited to, for insert, update, and delete.

@sqlquery()
def select_items(item_dict)
    return QueryData("INSERT INTO", template_params={'in__item_id':item_id_list})

@sqlexists

This wraps up a sql query conditionally and ultimately returns a boolean value to the caller. The query you give here can return anything you want but as good practice, try to always select as little as possible. For example, below we are just returning 1 because the value itself isn’t used, we just need to know there are records avaliable

@sqlquery()
def item_exists(item_id)
    return QueryData("SELECT 1 FROM table WHERE id=:id", query_params={'id':item_id})

Ultimately, the above query becomes “SELECT EXISTS (SELECT 1 FROM table WHERE id=:id)”. You’ll notice the inner select value isn’t actually used

Decorator templates

in template - this template will allow you to pass a list as a single parameter and have the IN condition build out for you. This allows you to more dynamically include values in your queries.

@sqlquery()
def select_items(item_id_list)
    return QueryData("SELECT * FROM table WHERE {in__item_id}",
                    template_params={'in__item_id':item_id_list})

not_in template - this template will allow you to pass a list as a single parameter and have the NOT IN condition build out for you. This allows you more dynamically exclude values in your queries.

@sqlquery()
def select_items(item_id_list)
    return QueryData("SELECT * FROM table WHERE {not_in__item_id}",
                    template_params={'not_in__item_id':item_id_list})

values template - when inserting and you have multiple records to insert, this allows you to pass multiple records for insert in a single INSERT statement

@sqlquery()
def insert_items(items)
    return QueryData("INSERT_INTO table(column_a, column_b) {values__items}",
                    template_params={'values__items':item_id_list})

You can write queries that contain templates and query_params used

@sqlquery()
def select_items(item_id_list, name)
    return QueryData("SELECT * FROM table WHERE {in__item_id} and name=:name",
                    template_params={'in__item_id':item_id_list},
                    query_params={'name': name})