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#include <Interpreters/WhereConstraintsOptimizer.h>
#include <Interpreters/TreeCNFConverter.h>
#include <Interpreters/ComparisonGraph.h>
#include <Parsers/IAST_fwd.h>
#include <Parsers/ASTFunction.h>
#include <Storages/StorageInMemoryMetadata.h>
#include <Interpreters/AddIndexConstraintsOptimizer.h>
#include <Parsers/ASTSelectQuery.h>
#include <Poco/Logger.h>
#include <Parsers/queryToString.h>
namespace DB
{
WhereConstraintsOptimizer::WhereConstraintsOptimizer(
ASTSelectQuery * select_query_,
const StorageMetadataPtr & metadata_snapshot_,
bool optimize_append_index_)
: select_query(select_query_)
, metadata_snapshot(metadata_snapshot_)
, optimize_append_index(optimize_append_index_)
{
}
namespace
{
enum class MatchState
{
FULL_MATCH, /// a = b
NOT_MATCH, /// a = not b
NONE, /// other
};
MatchState match(CNFQuery::AtomicFormula a, CNFQuery::AtomicFormula b)
{
bool match_means_ok = (a.negative == b.negative);
if (a.ast->getTreeHash() == b.ast->getTreeHash())
return match_means_ok ? MatchState::FULL_MATCH : MatchState::NOT_MATCH;
return MatchState::NONE;
}
bool checkIfGroupAlwaysTrueFullMatch(const CNFQuery::OrGroup & group, const ConstraintsDescription & constraints_description)
{
/// We have constraints in CNF.
/// CNF is always true => Each OR group in CNF is always true.
/// So, we try to check whether we have al least one OR group from CNF as subset in our group.
/// If we've found one then our group is always true too.
const auto & constraints_data = constraints_description.getConstraintData();
std::vector<size_t> found(constraints_data.size());
for (size_t i = 0; i < constraints_data.size(); ++i)
found[i] = constraints_data[i].size();
for (const auto & atom : group)
{
const auto constraint_atom_ids = constraints_description.getAtomIds(atom.ast);
if (constraint_atom_ids)
{
const auto constraint_atoms = constraints_description.getAtomsById(*constraint_atom_ids);
for (size_t i = 0; i < constraint_atoms.size(); ++i)
{
if (match(constraint_atoms[i], atom) == MatchState::FULL_MATCH)
{
if ((--found[(*constraint_atom_ids)[i].group_id]) == 0)
return true;
}
}
}
}
return false;
}
bool checkIfGroupAlwaysTrueGraph(const CNFQuery::OrGroup & group, const ComparisonGraph<ASTPtr> & graph)
{
/// We try to find at least one atom that is always true by using comparison graph.
for (const auto & atom : group)
{
const auto * func = atom.ast->as<ASTFunction>();
if (func && func->arguments->children.size() == 2)
{
const auto expected = ComparisonGraph<ASTPtr>::atomToCompareResult(atom);
if (graph.isAlwaysCompare(expected, func->arguments->children[0], func->arguments->children[1]))
return true;
}
}
return false;
}
bool checkIfAtomAlwaysFalseFullMatch(const CNFQuery::AtomicFormula & atom, const ConstraintsDescription & constraints_description)
{
const auto constraint_atom_ids = constraints_description.getAtomIds(atom.ast);
if (constraint_atom_ids)
{
for (const auto & constraint_atom : constraints_description.getAtomsById(*constraint_atom_ids))
{
const auto match_result = match(constraint_atom, atom);
if (match_result == MatchState::NOT_MATCH)
return true;
}
}
return false;
}
bool checkIfAtomAlwaysFalseGraph(const CNFQuery::AtomicFormula & atom, const ComparisonGraph<ASTPtr> & graph)
{
const auto * func = atom.ast->as<ASTFunction>();
if (func && func->arguments->children.size() == 2)
{
/// TODO: special support for !=
const auto expected = ComparisonGraph<ASTPtr>::atomToCompareResult(atom);
return !graph.isPossibleCompare(expected, func->arguments->children[0], func->arguments->children[1]);
}
return false;
}
void replaceToConstants(ASTPtr & term, const ComparisonGraph<ASTPtr> & graph)
{
const auto equal_constant = graph.getEqualConst(term);
if (equal_constant)
{
term = (*equal_constant)->clone();
}
else
{
for (auto & child : term->children)
replaceToConstants(child, graph);
}
}
CNFQuery::AtomicFormula replaceTermsToConstants(const CNFQuery::AtomicFormula & atom, const ComparisonGraph<ASTPtr> & graph)
{
CNFQuery::AtomicFormula result;
result.negative = atom.negative;
result.ast = atom.ast->clone();
replaceToConstants(result.ast, graph);
return result;
}
}
void WhereConstraintsOptimizer::perform()
{
if (select_query->where() && metadata_snapshot)
{
const auto & compare_graph = metadata_snapshot->getConstraints().getGraph();
auto cnf = TreeCNFConverter::toCNF(select_query->where());
cnf.pullNotOutFunctions()
.filterAlwaysTrueGroups([&compare_graph, this](const auto & group)
{
/// remove always true groups from CNF
return !checkIfGroupAlwaysTrueFullMatch(group, metadata_snapshot->getConstraints()) && !checkIfGroupAlwaysTrueGraph(group, compare_graph);
})
.filterAlwaysFalseAtoms([&compare_graph, this](const auto & atom)
{
/// remove always false atoms from CNF
return !checkIfAtomAlwaysFalseFullMatch(atom, metadata_snapshot->getConstraints()) && !checkIfAtomAlwaysFalseGraph(atom, compare_graph);
})
.transformAtoms([&compare_graph](const auto & atom)
{
return replaceTermsToConstants(atom, compare_graph);
})
.reduce()
.pushNotInFunctions();
if (optimize_append_index)
AddIndexConstraintsOptimizer(metadata_snapshot).perform(cnf);
select_query->setExpression(ASTSelectQuery::Expression::WHERE, TreeCNFConverter::fromCNF(cnf));
}
}
}
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