ClickHouse/dbms/src/DataStreams/PushingToViewsBlockOutputStream.cpp

#include <DataStreams/PushingToViewsBlockOutputStream.h>
#include <DataStreams/SquashingBlockInputStream.h>
#include <Interpreters/InterpreterSelectQuery.h>
#include <Storages/MergeTree/ReplicatedMergeTreeBlockOutputStream.h>


namespace DB
{

PushingToViewsBlockOutputStream::PushingToViewsBlockOutputStream(
    const String & database, const String & table, const StoragePtr & storage,
    const Context & context_, const ASTPtr & query_ptr_, bool no_destination)
    : context(context_), query_ptr(query_ptr_)
{
    /** TODO This is a very important line. At any insertion into the table one of streams should own lock.
      * Although now any insertion into the table is done via PushingToViewsBlockOutputStream,
      *  but it's clear that here is not the best place for this functionality.
      */
    addTableLock(storage->lockStructure(true, __PRETTY_FUNCTION__));

    /// If the "root" table deduplactes blocks, there are no need to make deduplication for children
    /// Moreover, deduplication for AggregatingMergeTree children could produce false positives due to low size of inserting blocks
    bool disable_deduplication_for_children = !no_destination && storage->supportsDeduplication();

    if (!table.empty())
    {
        Dependencies dependencies = context.getDependencies(database, table);

        /// We need special context for materialized views insertions
        if (!dependencies.empty())
        {
            views_context = std::make_unique<Context>(context);
            // Do not deduplicate insertions into MV if the main insertion is Ok
            if (disable_deduplication_for_children)
                views_context->getSettingsRef().insert_deduplicate = false;
        }

        for (const auto & database_table : dependencies)
        {
            auto dependent_table = context.getTable(database_table.first, database_table.second);
            auto & materialized_view = dynamic_cast<const StorageMaterializedView &>(*dependent_table);

            auto query = materialized_view.getInnerQuery();
            BlockOutputStreamPtr out = std::make_shared<PushingToViewsBlockOutputStream>(
                database_table.first, database_table.second, dependent_table, *views_context, ASTPtr());
            views.emplace_back(ViewInfo{std::move(query), database_table.first, database_table.second, std::move(out)});
        }
    }

    /* Do not push to destination table if the flag is set */
    if (!no_destination)
    {
        output = storage->write(query_ptr, context.getSettingsRef());
        replicated_output = dynamic_cast<ReplicatedMergeTreeBlockOutputStream *>(output.get());
    }
}


void PushingToViewsBlockOutputStream::write(const Block & block)
{
    if (output)
        output->write(block);

    /// Don't process materialized views if this block is duplicate
    if (replicated_output && replicated_output->lastBlockIsDuplicate())
        return;

    /// Insert data into materialized views only after successful insert into main table
    for (auto & view : views)
    {
        try
        {
            BlockInputStreamPtr from = std::make_shared<OneBlockInputStream>(block);
            InterpreterSelectQuery select(view.query, *views_context, from);
            BlockInputStreamPtr in = std::make_shared<MaterializingBlockInputStream>(select.execute().in);
            /// Squashing is needed here because the materialized view query can generate a lot of blocks
            /// even when only one block is inserted into the parent table (e.g. if the query is a GROUP BY
            /// and two-level aggregation is triggered).
            in = std::make_shared<SquashingBlockInputStream>(
                in, context.getSettingsRef().min_insert_block_size_rows, context.getSettingsRef().min_insert_block_size_bytes);

            in->readPrefix();

            while (Block result_block = in->read())
                view.out->write(result_block);

            in->readSuffix();
        }
        catch (Exception & ex)
        {
            ex.addMessage("while pushing to view " + view.database + "." + view.table);
            throw;
        }
    }
}

void PushingToViewsBlockOutputStream::writePrefix()
{
    if (output)
        output->writePrefix();

    for (auto & view : views)
    {
        try
        {
            view.out->writePrefix();
        }
        catch (Exception & ex)
        {
            ex.addMessage("while write prefix to view " + view.database + "." + view.table);
            throw;
        }
    }
}

void PushingToViewsBlockOutputStream::writeSuffix()
{
    if (output)
        output->writeSuffix();

    for (auto & view : views)
    {
        try
        {
            view.out->writeSuffix();
        }
        catch (Exception & ex)
        {
            ex.addMessage("while write prefix to view " + view.database + "." + view.table);
            throw;
        }
    }
}

void PushingToViewsBlockOutputStream::flush()
{
    if (output)
        output->flush();

    for (auto & view : views)
        view.out->flush();
}

}