huatw / EMF-SQL

simple compiler to transform ESQL into java file.

EMF-Query

About

ESQL -> JAVA CODE -> Query Result

ESQL

SELECT prod, month, count(z.quant)
FROM sales
GROUP BY prod, month; x, y, z
SUCH THAT x.prod = prod and x.month = x.month-1,
          y.prod = prod and y.month = y.month+1,
          z.prod = prod and z.month = month 
                        and z.sale > avg(x.sale) 
                        and z.sale < avg(y.sale)

QUERY INFORMATION(PHI and more)

• PROJECTIONS: prod, month, count(z.quant)
• GROUPING ATTRIBUTES: prod, month
• GROUPING VARAIBLES:
  1. x.prod = prod and x.month = x.month-1
  2. y.prod = prod and y.month = y.month+1
  3. z.prod = prod and z.month = month and z.sale > avg(x.sale) and z.sale < avg(y.sale)
• HAVING: None
• WHERE: None

CODE GENERATION

parts of generated code:

• static parts:

  1. database setup: connect close queryAll
  2. helper: compare varaible

• dynamically generated:

  1. mf-table: aggregate fns, grouping attributes
  2. main fn: init mf table / update aggregates / output

LIMITATION:

• suchthat having transformation(naive replacement -> parsing)
• ESQL error checking, handling(parsing needed)

USAGE

See QTest.java file for examples.