[PIG-1399] Logical Optimizer: Expression optimizor rule

• Type: Sub-task
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.7.0
• Fix Version/s: 0.8.0
• Component/s: impl

Release Note

This logical simplification contains the following types of simplifications:

1) Constant pre-calculation
Example:
B = filter A by a0 > 5+7;

is simplified to

B = filter A by a0 > 12;


2) Elimination of negations
Example:
B = filter A by not (not(a0>5) or a>10);

is simplified to

B = filter A by a0>5 and a<=10;


3) Elimination of logical implied expression in AND
Example:
B = filter A by (a0 > 5 and a0 > 7);


is simplified to

B = filter A by a0 > 7;


4) Elimination of logical implied expression in OR
Example:
B = filter A by ((a0 > 5) or (a0 > 6 and a1 > 15);

is simplified to
B = filter C by a0 > 5;


5) Equivalence elimination
Example:
B = filter A by (a0 > 5 and a0 > 5);

is simplified to

B = filter A by a0 > 5;


6) Elimination of complementary expressions in OR
Example:
B = filter A by (a0 > 5 OR a0 <= 5);

is simplified to non-filtering


7) Elimination of naive TRUE expression
Example:

B = filter A by 1==1;

is simplified to non-filtering

• Assignee: Yan Zhou
• Reporter: Daniel Dai
• Created: 30/Apr/10 18:05
• Updated: 17/Dec/10 22:44
• Resolved: 01/Sep/10 20:36

Description

We can optimize expression in several ways:

1. Constant pre-calculation
Example:
B = filter A by a0 > 5+7;
=> B = filter A by a0 > 12;

2. Boolean expression optimization
Example:
B = filter A by not (not(a0>5) or a>10);
=> B = filter A by a0>5 and a<=10;