souffle::ram::transform::IfConversionTransformer Class Reference

Convert IndexScan operations to Filter/Existence Checks. More...

#include <IfConversion.h>

Inheritance diagram for souffle::ram::transform::IfConversionTransformer:

Collaboration diagram for souffle::ram::transform::IfConversionTransformer:

Public Member Functions
bool	convertIndexScans (Program &program)
	Apply if-conversion to the whole program. More...
std::string	getName () const override
	@Brief get name of the transformer More...
Own< Operation >	rewriteIndexScan (const IndexScan *indexScan)
	Rewrite IndexScan operations. More...
Public Member Functions inherited from souffle::ram::transform::Transformer
bool	apply (TranslationUnit &translationUnit)
	@Brief apply the transformer to a translation unit @Param translationUnit that will be transformed. More...
virtual	~Transformer ()=default

Protected Member Functions
bool	transform (TranslationUnit &translationUnit) override
	@Brief transform the translation unit / used by apply @Param translationUnit that will be transformed. More...

Detailed Description

Convert IndexScan operations to Filter/Existence Checks.

If there exists IndexScan operations in the RAM, and their tuples are not further used in subsequent operations, the IndexScan operations will be rewritten to Filter/Existence Checks.

For example,

QUERY
 ...
 FOR t1 IN X ON INDEX t1.x = 10 AND t1.y = 20
   ... // no occurrence of t1

will be rewritten to

QUERY
 ...
  IF (10,20) NOT IN A
    ...

Definition at line 58 of file IfConversion.h.

Member Function Documentation

convertIndexScans()

bool souffle::ram::transform::IfConversionTransformer::convertIndexScans

(

Program &

program

)

Apply if-conversion to the whole program.

Parameters

RAM

program

Returns

A flag indicating whether the RAM program has been changed.

Search for queries and rewrite their IndexScan operations if possible.

Definition at line 80 of file IfConversion.cpp.

                                                                              {
                if (Own<Operation> op = rewriteIndexScan(scan)) {
                    changed = true;
                    node = std::move(op);
                }
            }
            node->apply(makeLambdaRamMapper(scanRewriter));
            return node;
        };
        const_cast<Query*>(&query)->apply(makeLambdaRamMapper(scanRewriter));
    });
    return changed;
}
 
}  // namespace souffle::ram::transform

References rewriteIndexScan().

Here is the call graph for this function:

getName()

std::string souffle::ram::transform::IfConversionTransformer::getName ( ) const

inlineoverridevirtual

@Brief get name of the transformer

Implements souffle::ram::transform::Transformer.

Definition at line 60 of file IfConversion.h.

         :
    bool transform(TranslationUnit& translationUnit) override {

rewriteIndexScan()

Own< Operation > souffle::ram::transform::IfConversionTransformer::rewriteIndexScan

(

const IndexScan *

indexScan

)

Rewrite IndexScan operations.

Parameters

indexScan

An index operation

Returns

The old operation if the if-conversion fails; otherwise the filter/existence check

Rewrites IndexScan operations to a filter/existence check if the IndexScan's tuple is not used in a consecutive RAM operation

Definition at line 37 of file IfConversion.cpp.

                                                             {
            tupleNotUsed = false;
        }
    });
 
    // if not used, transform the IndexScan operation to an existence check
    if (tupleNotUsed) {
        // replace IndexScan with an Filter/Existence check
        VecOwn<Expression> newValues;
 
        size_t arity = indexScan->getRangePattern().first.size();
        for (size_t i = 0; i < arity; ++i) {
            if (*(indexScan->getRangePattern().first[i]) != *(indexScan->getRangePattern().second[i])) {
                return nullptr;
            }
        }
 
        for (auto& cur : indexScan->getRangePattern().second) {
            Expression* val = nullptr;
            if (cur != nullptr) {
                val = cur->clone();
            }
            newValues.emplace_back(val);
        }
 
        // check if there is a break statement nested in the Scan - if so, remove it
        Operation* newOp;
        if (const auto* breakOp = dynamic_cast<const Break*>(&indexScan->getOperation())) {
            newOp = breakOp->getOperation().clone();
        } else {
            newOp = indexScan->getOperation().clone();
        }
 
        return mk<Filter>(mk<ExistenceCheck>(indexScan->getRelation(), std::move(newValues)),
                Own<Operation>(newOp), indexScan->getProfileText());
    }
    return nullptr;
}
 
bool IfConversionTransformer::convertIndexScans(Program& program) {
    bool changed = false;
    visitDepthFirst(program, [&](const Query& query) {

Referenced by convertIndexScans().

transform()

bool souffle::ram::transform::IfConversionTransformer::transform ( TranslationUnit &  translationUnit )

inlineoverrideprotectedvirtual

@Brief transform the translation unit / used by apply @Param translationUnit that will be transformed.

@Return flag reporting whether the RAM program has changed

Implements souffle::ram::transform::Transformer.

Definition at line 84 of file IfConversion.h.

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The documentation for this class was generated from the following files:

• ram/transform/IfConversion.h
• ram/transform/IfConversion.cpp