Examples with LimitClause org.apache.asterix.lang.common.clause.LimitClause used on opensource projects

Example 1 with LimitClause

use of org.apache.asterix.lang.common.clause.LimitClause in project asterixdb by apache.

the class SqlppGroupByVisitor method visit.

@Override
public Expression visit(SelectBlock selectBlock, ILangExpression arg) throws CompilationException {
    // Traverses the select block in the order of "from", "let"s, "where",
    // "group by", "let"s, "having" and "select".
    FromClause fromClause = selectBlock.getFromClause();
    if (selectBlock.hasFromClause()) {
        fromClause.accept(this, arg);
    }
    if (selectBlock.hasLetClauses()) {
        List<LetClause> letList = selectBlock.getLetList();
        for (LetClause letClause : letList) {
            letClause.accept(this, arg);
        }
    }
    if (selectBlock.hasWhereClause()) {
        selectBlock.getWhereClause().accept(this, arg);
    }
    if (selectBlock.hasGroupbyClause()) {
        GroupbyClause groupbyClause = selectBlock.getGroupbyClause();
        groupbyClause.accept(this, fromClause);
        Collection<VariableExpr> visibleVarsInCurrentScope = SqlppVariableUtil.getBindingVariables(groupbyClause);
        VariableExpr groupVar = groupbyClause.getGroupVar();
        Set<VariableExpr> groupFieldVars = getGroupFieldVariables(groupbyClause);
        Collection<VariableExpr> freeVariablesInGbyLets = new HashSet<>();
        if (selectBlock.hasLetClausesAfterGroupby()) {
            List<LetClause> letListAfterGby = selectBlock.getLetListAfterGroupby();
            for (LetClause letClauseAfterGby : letListAfterGby) {
                letClauseAfterGby.accept(this, arg);
                // Rewrites each let clause after the group-by.
                SqlppRewriteUtil.rewriteExpressionUsingGroupVariable(groupVar, groupFieldVars, letClauseAfterGby, context);
                Collection<VariableExpr> freeVariablesInLet = SqlppVariableUtil.getFreeVariables(letClauseAfterGby.getBindingExpr());
                freeVariablesInLet.removeAll(visibleVarsInCurrentScope);
                freeVariablesInGbyLets.addAll(freeVariablesInLet);
                visibleVarsInCurrentScope.add(letClauseAfterGby.getVarExpr());
            }
        }
        Collection<VariableExpr> freeVariables = new HashSet<>();
        if (selectBlock.hasHavingClause()) {
            // Rewrites the having clause.
            HavingClause havingClause = selectBlock.getHavingClause();
            havingClause.accept(this, arg);
            SqlppRewriteUtil.rewriteExpressionUsingGroupVariable(groupVar, groupFieldVars, havingClause, context);
            freeVariables.addAll(SqlppVariableUtil.getFreeVariables(havingClause));
        }
        SelectExpression parentSelectExpression = (SelectExpression) arg;
        // We cannot rewrite ORDER BY and LIMIT if it's a SET operation query.
        if (!parentSelectExpression.getSelectSetOperation().hasRightInputs()) {
            if (parentSelectExpression.hasOrderby()) {
                // Rewrites the ORDER BY clause.
                OrderbyClause orderbyClause = parentSelectExpression.getOrderbyClause();
                orderbyClause.accept(this, arg);
                SqlppRewriteUtil.rewriteExpressionUsingGroupVariable(groupVar, groupFieldVars, orderbyClause, context);
                freeVariables.addAll(SqlppVariableUtil.getFreeVariables(orderbyClause));
            }
            if (parentSelectExpression.hasLimit()) {
                // Rewrites the LIMIT clause.
                LimitClause limitClause = parentSelectExpression.getLimitClause();
                limitClause.accept(this, arg);
                SqlppRewriteUtil.rewriteExpressionUsingGroupVariable(groupVar, groupFieldVars, limitClause, context);
                freeVariables.addAll(SqlppVariableUtil.getFreeVariables(limitClause));
            }
        }
        // Visits the select clause.
        SelectClause selectClause = selectBlock.getSelectClause();
        selectClause.accept(this, arg);
        // Rewrites the select clause.
        SqlppRewriteUtil.rewriteExpressionUsingGroupVariable(groupVar, groupFieldVars, selectClause, context);
        freeVariables.addAll(SqlppVariableUtil.getFreeVariables(selectClause));
        freeVariables.removeAll(visibleVarsInCurrentScope);
        // Gets the final free variables.
        freeVariables.addAll(freeVariablesInGbyLets);
        // Gets outer scope variables.
        Collection<VariableExpr> decorVars = SqlppVariableUtil.getLiveVariables(scopeChecker.getCurrentScope(), true);
        decorVars.removeAll(visibleVarsInCurrentScope);
        // Need path resolution or not?
        boolean needResolution = !decorVars.containsAll(freeVariables);
        // Otherwise, we only need to retain used free variables.
        if (needResolution) {
            // Tracks used variables, including WITH variables.
            decorVars.retainAll(freeVariables);
            // Adds all non-WITH outer scope variables, for path resolution.
            Collection<VariableExpr> visibleOuterScopeNonWithVars = SqlppVariableUtil.getLiveVariables(scopeChecker.getCurrentScope(), false);
            visibleOuterScopeNonWithVars.removeAll(visibleVarsInCurrentScope);
            decorVars.addAll(visibleOuterScopeNonWithVars);
        } else {
            // Only retains used free variables.
            decorVars.retainAll(freeVariables);
        }
        if (!decorVars.isEmpty()) {
            // Adds used WITH variables.
            Collection<VariableExpr> visibleOuterScopeNonWithVars = SqlppVariableUtil.getLiveVariables(scopeChecker.getCurrentScope(), false);
            visibleOuterScopeNonWithVars.retainAll(freeVariables);
            decorVars.addAll(visibleOuterScopeNonWithVars);
            // Adds necessary decoration variables for the GROUP BY.
            // NOTE: we need to include WITH binding variables so as they can be evaluated before
            // the GROUP BY instead of being inlined as part of nested pipepline. The current optimzier
            // is not able to optimize the latter case. The following query is such an example:
            // asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/dapd/q2-11
            List<GbyVariableExpressionPair> decorList = new ArrayList<>();
            for (VariableExpr var : decorVars) {
                decorList.add(new GbyVariableExpressionPair((VariableExpr) SqlppRewriteUtil.deepCopy(var), (Expression) SqlppRewriteUtil.deepCopy(var)));
            }
            groupbyClause.getDecorPairList().addAll(decorList);
        }
    } else {
        selectBlock.getSelectClause().accept(this, arg);
    }
    return null;
}

Example 2 with LimitClause

use of org.apache.asterix.lang.common.clause.LimitClause in project asterixdb by apache.

the class SetOperationVisitor method visit.

@Override
public Expression visit(SelectExpression selectExpression, ILangExpression arg) throws CompilationException {
    // Recursively visit nested select expressions.
    SelectSetOperation selectSetOperation = selectExpression.getSelectSetOperation();
    if (!selectSetOperation.hasRightInputs() || !(selectExpression.hasOrderby() || selectExpression.hasLimit())) {
        return super.visit(selectExpression, arg);
    }
    OrderbyClause orderBy = selectExpression.getOrderbyClause();
    LimitClause limit = selectExpression.getLimitClause();
    // Wraps the set operation part with a subquery.
    SelectExpression nestedSelectExpression = new SelectExpression(null, selectSetOperation, null, null, true);
    // Binding variable for the subquery.
    VariableExpr newBindingVar = new VariableExpr(context.newVariable());
    FromTerm newFromTerm = new FromTerm(nestedSelectExpression, newBindingVar, null, null);
    FromClause newFromClause = new FromClause(new ArrayList<>(Collections.singletonList(newFromTerm)));
    SelectClause selectClause = new SelectClause(new SelectElement(newBindingVar), null, false);
    SelectBlock selectBlock = new SelectBlock(selectClause, newFromClause, null, null, null, null, null);
    SelectSetOperation newSelectSetOperation = new SelectSetOperation(new SetOperationInput(selectBlock, null), null);
    // Puts together the generated select-from-where query and order by/limit.
    SelectExpression newSelectExpression = new SelectExpression(selectExpression.getLetList(), newSelectSetOperation, orderBy, limit, selectExpression.isSubquery());
    return super.visit(newSelectExpression, arg);
}

Example 3 with LimitClause

use of org.apache.asterix.lang.common.clause.LimitClause in project asterixdb by apache.

the class DeepCopyVisitor method visit.

@Override
public LimitClause visit(LimitClause limitClause, Void arg) throws CompilationException {
    Expression limitExpr = (Expression) limitClause.getLimitExpr().accept(this, arg);
    Expression offsetExpr = limitClause.hasOffset() ? (Expression) limitClause.getOffset().accept(this, arg) : null;
    return new LimitClause(limitExpr, offsetExpr);
}

Example 4 with LimitClause

use of org.apache.asterix.lang.common.clause.LimitClause in project asterixdb by apache.

the class DeepCopyVisitor method visit.

@Override
public SelectExpression visit(SelectExpression selectExpression, Void arg) throws CompilationException {
    List<LetClause> lets = new ArrayList<>();
    SelectSetOperation select;
    OrderbyClause orderby = null;
    LimitClause limit = null;
    // visit let list
    if (selectExpression.hasLetClauses()) {
        for (LetClause letClause : selectExpression.getLetList()) {
            lets.add((LetClause) letClause.accept(this, arg));
        }
    }
    // visit the main select.
    select = (SelectSetOperation) selectExpression.getSelectSetOperation().accept(this, arg);
    // visit order by
    if (selectExpression.hasOrderby()) {
        List<Expression> orderExprs = new ArrayList<>();
        for (Expression orderExpr : selectExpression.getOrderbyClause().getOrderbyList()) {
            orderExprs.add((Expression) orderExpr.accept(this, arg));
        }
        orderby = new OrderbyClause(orderExprs, selectExpression.getOrderbyClause().getModifierList());
    }
    // visit limit
    if (selectExpression.hasLimit()) {
        limit = (LimitClause) selectExpression.getLimitClause().accept(this, arg);
    }
    return new SelectExpression(lets, select, orderby, limit, selectExpression.isSubquery());
}

Example 5 with LimitClause

use of org.apache.asterix.lang.common.clause.LimitClause in project asterixdb by apache.

the class SqlppCloneAndSubstituteVariablesVisitor method visit.

@Override
public Pair<ILangExpression, VariableSubstitutionEnvironment> visit(SelectExpression selectExpression, VariableSubstitutionEnvironment env) throws CompilationException {
    boolean subquery = selectExpression.isSubquery();
    List<LetClause> newLetList = new ArrayList<>();
    SelectSetOperation newSelectSetOperation;
    OrderbyClause newOrderbyClause = null;
    LimitClause newLimitClause = null;
    VariableSubstitutionEnvironment currentEnv = env;
    Pair<ILangExpression, VariableSubstitutionEnvironment> p;
    if (selectExpression.hasLetClauses()) {
        for (LetClause letClause : selectExpression.getLetList()) {
            p = letClause.accept(this, currentEnv);
            newLetList.add(letClause);
            currentEnv = p.second;
        }
    }
    p = selectExpression.getSelectSetOperation().accept(this, env);
    newSelectSetOperation = (SelectSetOperation) p.first;
    currentEnv = p.second;
    if (selectExpression.hasOrderby()) {
        p = selectExpression.getOrderbyClause().accept(this, currentEnv);
        newOrderbyClause = (OrderbyClause) p.first;
        currentEnv = p.second;
    }
    if (selectExpression.hasLimit()) {
        p = selectExpression.getLimitClause().accept(this, currentEnv);
        newLimitClause = (LimitClause) p.first;
        currentEnv = p.second;
    }
    return new Pair<>(new SelectExpression(newLetList, newSelectSetOperation, newOrderbyClause, newLimitClause, subquery), currentEnv);
}