Java 类com.facebook.presto.sql.tree.SearchedCaseExpression 实例源码

@Override
protected String visitSearchedCaseExpression(SearchedCaseExpression node, Void context)
{
    ImmutableList.Builder<String> parts = ImmutableList.builder();
    parts.add("CASE").add("\n");
    for (WhenClause whenClause : node.getWhenClauses()) {
        parts.add(process(whenClause, context)).add("\n");
    }
    if (node.getDefaultValue() != null) {
        parts.add("ELSE")
                .add(process(node.getDefaultValue(), context)).add("\n");
    }
    parts.add("END").add("\n");

    return "(" + Joiner.on(' ').join(parts.build()) + ")";
}

@Override
protected String visitSearchedCaseExpression(SearchedCaseExpression node, StackableAstVisitorContext<Integer> indent)
{
    ImmutableList.Builder<String> parts = ImmutableList.builder();
    parts.add("CASE");
    for (WhenClause whenClause : node.getWhenClauses()) {
        parts.add(process(whenClause, indent));
    }

    node.getDefaultValue()
            .ifPresent((value) -> parts.add("ELSE").add(process(value, indent)));

    parts.add("END");

    return "(" + Joiner.on(' ').join(parts.build()) + ")";
}

@Override
protected String visitSearchedCaseExpression(SearchedCaseExpression node, Boolean unmangleNames)
{
    ImmutableList.Builder<String> parts = ImmutableList.builder();
    parts.add("CASE");
    for (WhenClause whenClause : node.getWhenClauses()) {
        parts.add(process(whenClause, unmangleNames));
    }

    node.getDefaultValue()
            .ifPresent((value) -> parts.add("ELSE").add(process(value, unmangleNames)));

    parts.add("END");

    return "(" + Joiner.on(' ').join(parts.build()) + ")";
}

@Override
protected String visitSearchedCaseExpression(SearchedCaseExpression node, Boolean unmangleNames)
{
    ImmutableList.Builder<String> parts = ImmutableList.builder();
    parts.add("CASE");
    for (WhenClause whenClause : node.getWhenClauses()) {
        parts.add(process(whenClause, unmangleNames));
    }

    node.getDefaultValue()
            .ifPresent((value) -> parts.add("ELSE").add(process(value, unmangleNames)));

    parts.add("END");

    return "(" + Joiner.on(' ').join(parts.build()) + ")";
}

protected static String processFuncNullifzero(Formatter formatter, FunctionCall node) {
    Expression x = node.getArguments().get(0);

    List<WhenClause> listWhen = new ArrayList<WhenClause>();
    ComparisonExpression ce = new ComparisonExpression(ComparisonExpression.Type.EQUAL, x, new LongLiteral("0"));
    WhenClause wc = new WhenClause(ce, new NullLiteral());
    listWhen.add(wc);
    SearchedCaseExpression sce = new SearchedCaseExpression(listWhen, x);
    return formatter.process(sce, null);
}

@Override
protected RowExpression visitSearchedCaseExpression(SearchedCaseExpression node, Void context)
{
    /*
        Translates an expression like:

            case when cond1 then value1
                 when cond2 then value2
                 when cond3 then value3
                 else value4
            end

        To:

            IF(cond1,
                value1,
                IF(cond2,
                    value2,
                        If(cond3,
                            value3,
                            value4)))

     */
    RowExpression expression = node.getDefaultValue()
            .map((value) -> process(value, context))
            .orElse(constantNull(types.get(node)));

    for (WhenClause clause : Lists.reverse(node.getWhenClauses())) {
        expression = call(
                Signatures.ifSignature(types.get(node)),
                types.get(node),
                process(clause.getOperand(), context),
                process(clause.getResult(), context),
                expression);
    }

    return expression;
}

@Override
protected Object visitSearchedCaseExpression(SearchedCaseExpression node, Object context)
{
    Object defaultResult = processWithExceptionHandling(node.getDefaultValue().orElse(null), context);

    List<WhenClause> whenClauses = new ArrayList<>();
    for (WhenClause whenClause : node.getWhenClauses()) {
        Object whenOperand = processWithExceptionHandling(whenClause.getOperand(), context);
        Object result = processWithExceptionHandling(whenClause.getResult(), context);

        if (whenOperand instanceof Expression) {
            // cannot fully evaluate, add updated whenClause
            whenClauses.add(new WhenClause(
                    toExpression(whenOperand, type(whenClause.getOperand())),
                    toExpression(result, type(whenClause.getResult()))));
        }
        else if (Boolean.TRUE.equals(whenOperand)) {
            // condition is true, use this as defaultResult
            defaultResult = result;
            break;
        }
    }

    if (whenClauses.isEmpty()) {
        return defaultResult;
    }

    Expression resultExpression = (defaultResult == null) ? null : toExpression(defaultResult, type(node));
    return new SearchedCaseExpression(whenClauses, Optional.ofNullable(resultExpression));
}

@Override
public Expression rewriteIfExpression(IfExpression node, Void context, ExpressionTreeRewriter<Void> treeRewriter)
{
    Expression condition = treeRewriter.rewrite(node.getCondition(), context);
    Expression trueValue = treeRewriter.rewrite(node.getTrueValue(), context);

    Optional<Expression> falseValue = node.getFalseValue()
            .map((value) -> treeRewriter.rewrite(value, context));

    return new SearchedCaseExpression(ImmutableList.of(new WhenClause(condition, trueValue)), falseValue);
}

@Override
protected Boolean visitSearchedCaseExpression(SearchedCaseExpression node, Void context)
{
    for (WhenClause whenClause : node.getWhenClauses()) {
        if (!process(whenClause.getOperand(), context) || !process(whenClause.getResult(), context)) {
            return false;
        }
    }

    return !node.getDefaultValue().isPresent() || process(node.getDefaultValue().get(), context);
}

@Override
public Node visitSearchedCase(SqlBaseParser.SearchedCaseContext context)
{
    return new SearchedCaseExpression(
            getLocation(context),
            visit(context.whenClause(), WhenClause.class),
            visitIfPresent(context.elseExpression, Expression.class));
}

@Override
protected OrderBy visitSortItem(SortItem si, QueryState state){
    String orderKey = null;
    if(si.getSortKey() instanceof DereferenceExpression){
        orderKey = SelectParser.visitDereferenceExpression((DereferenceExpression)si.getSortKey());
    }else if (si.getSortKey() instanceof FunctionCall){
        orderKey = si.getSortKey().toString().replaceAll("\"","");
    }else if(si.getSortKey() instanceof SearchedCaseExpression){
        //... order by CASE WHEN field IS NULL THEN 1 ELSE 0 END
        // TODO: improve this quick and dirty implementation
        SearchedCaseExpression sce = (SearchedCaseExpression)si.getSortKey();
        for(WhenClause when : sce.getWhenClauses()){
            orderKey = SelectParser.visitDereferenceExpression(
                    (DereferenceExpression)((IsNullPredicate)when.getOperand()).getValue());
        }
    }else if(si.getSortKey() instanceof QualifiedNameReference){
        orderKey = ((QualifiedNameReference)si.getSortKey()).getName().toString();
    }else {
        state.addException("Order statement with type '"+si.getSortKey().getClass().getName()+"' is not supported");
        return null;
    }
    // fix case
    orderKey = Heading.findOriginal(state.originalSql()+";", orderKey, "order by.+", "\\W");
    // remove any table reference or alias
    if(orderKey.contains(".")){
        String prefix = orderKey.split("\\.")[0];
        for(QuerySource tr : state.getSources()){
            if(tr.getAlias() != null){
                if(prefix.equals(tr.getAlias())) orderKey = orderKey.substring(orderKey.indexOf('.')+1);
            }else if (tr.getSource() != null && prefix.equals(tr.getSource())) orderKey = orderKey.substring(orderKey.indexOf('.')+1);
        }
    }
    // select column to order on
    Column column = state.getHeading().getColumnByLabel(orderKey);
    if(column != null){
        if(si.getOrdering().toString().startsWith("ASC")){
            return new OrderBy(column.getColumn(), SortOrder.ASC, column.getIndex());
        }else{
            return new OrderBy(column.getColumn(), SortOrder.DESC, column.getIndex());
        }
    }else{
        state.addException("Order key '"+orderKey+"' is not specified in SELECT clause");
        return null;
    }
}

public static Expression caseWhen(Expression operand, Expression result)
{
    return new SearchedCaseExpression(ImmutableList.of(new WhenClause(operand, result)), Optional.empty());
}