pikaQ 0.0.1

Programmatically generate SQL queries for different database platforms.

pikaQ

This library is heavily inspired by PyPika, so a lot of the syntax is based on how PyPika works. Just like PyPika, PikaQ replaces handwritten SQL queries with programmatic construction of queries. The main difference is that pikaQ is designed solve the problem of writing the same code that can be parsed to different SQL dialects. This is done by using a common syntax that is then translated to the specific dialect.

This library provides the core components and implementation for constructing the Select query and the core mechanism for parsing it into different dialect. It does not offer complete coverage of SQL syntax nor the detailed implementation of all the dialects. However, it should be easy to extend the library to support more SQL syntax and other types of queries you want to construct.

Validation of SQL correctness is not an explicit goal of PikaQ. You are encouraged to check inputs you provide to PyPika or appropriately handle errors raised from your SQL database - just as you would have if you were writing SQL yourself.

Install

pip install pikaQ

How to use

For example, if we want to write the same query in Spark SQL and AWS Athena, we might encounter this problem: we have ADD_MONTHS function in Spark SQL, but in AWS Athena (Presto) we don’t have this function.

We can define an ADD_MONTHS function in the following way:

from pikaQ.terms import custom_func
from pikaQ.queries import Query


@custom_func
def add_months(column, value, dialect='spark'):
    if dialect == 'athena':
        return f"DATE_ADD('month', {value}, {column})"
    elif dialect == 'spark':
        return f'ADD_MONTH({column}, {value})'
    else:
        raise ValueError(f'Unsupported dialect: {dialect}')


q = (Query.from_('table')
        .select('col1', add_months('col2', 3).as_('col2'))
)

Then we can generate the query for Spark SQL and AWS Athena:

print(q.get_sql(dialect='athena'))

select col1, DATE_ADD('month', 3, col2) AS col2
from table

print(q.get_sql(dialect='spark'))

select col1, ADD_MONTH(col2, 3) AS col2
from table

A more complex example to show how the syntax works:

from pikaQ.queries import Query, Table, Field, AliasedQuery
from pikaQ.terms import Case, Preceding, CURRENT_ROW
import pikaQ.functions as fn


a = Table('tbl1').as_('a')
b = Table('tbl2').as_('b')
s = AliasedQuery('s')
m = AliasedQuery('m')
v = AliasedQuery('v')

q0 = (Query
      .from_(a)
      .select(
         a.col1,
         a.col2,
         fn.Sum(a.col3).over(b.col2).rows(Preceding(3), CURRENT_ROW).as_('total'), 
         fn.RowNumber().over(b.col2).orderby(b.col4).as_('row_num')
      ).distinct()
      .where((Field('col2')-100>2) & (Field('col3')/9<=1))
      .orderby(b.col2)
)
q1 = (Query
      .from_(b)
      .select(b.col1, b.col2, fn.Avg(b.col3).as_('avg'))
      .groupby(b.col1, b.col2)
      .having(fn.Count(b.col3)>2)
)

q = (Query
     .with_(q0, 's')
     .with_(Query
         .from_(s)
         .select(s.star())
         .where(s.row_num == 1), 'm')
     .with_(q1, 'v')
     .from_('v')
     .join('m')
        .on(
            (v.col1 == m.col1) &
            (v.col2 == m.col2)
            )
     .select(
         v.col1, v.col2, v.avg,
         Case().when(m.total>100, 1).else_(0).as_('flag')
         )
)

print(q.get_sql())

with s as (
select distinct a.col1, a.col2, SUM(a.col3) OVER (PARTITION BY b.col2 ROWS BETWEEN 3 PRECEDING AND CURRENT_ROW) AS total, ROW_NUMBER() OVER (PARTITION BY b.col2 ORDER BY b.col4) AS row_num
from tbl1 as a
where col2 - 100 > 2 and col3 / 9 <= 1
order by b.col2)

, m as (
select s.*
from s
where s.row_num = 1)

, v as (
select b.col1, b.col2, AVG(b.col3)
from tbl2 as b
group by b.col1, b.col2
having COUNT(b.col3) > 2)

select v.col1, v.col2, v.avg, CASE
WHEN m.total > 100 THEN 1
ELSE 0
END AS flag
from v
join m on v.col1 = m.col1 and v.col2 = m.col2

For more syntax examples, please refer to the docs.

Extension

One can use the core components and logic implemented in this library to extend the functionality to support more SQL syntax and other types of queries. For details of how to extend the SelectQuery to support more clauses, please refer to the Query section of the docs.