ClickHouse/dbms/include/DB/Dictionaries/MySQLDictionarySource.h

162 lines
4.1 KiB
C++

#pragma once
#include <DB/Dictionaries/IDictionarySource.h>
#include <DB/Dictionaries/MySQLBlockInputStream.h>
#include <statdaemons/ext/range.hpp>
#include <mysqlxx/Pool.h>
#include <Poco/Util/AbstractConfiguration.h>
#include <strconvert/escape.h>
namespace DB
{
/// Allows loading dictionaries from a MySQL database
class MySQLDictionarySource final : public IDictionarySource
{
static const auto max_block_size = 8192;
public:
MySQLDictionarySource(const Poco::Util::AbstractConfiguration & config, const std::string & config_prefix,
Block & sample_block)
: table{config.getString(config_prefix + ".table")},
sample_block{sample_block},
pool{config, config_prefix},
load_all_query{composeLoadAllQuery(sample_block, table)},
last_modification{getLastModification()}
{}
/// copy-constructor is provided in order to support cloneability
MySQLDictionarySource(const MySQLDictionarySource & other)
: table{other.table},
sample_block{other.sample_block},
pool{other.pool},
load_all_query{other.load_all_query}, last_modification{other.last_modification}
{}
BlockInputStreamPtr loadAll() override
{
last_modification = getLastModification();
return new MySQLBlockInputStream{pool.Get(), load_all_query, sample_block, max_block_size};
}
BlockInputStreamPtr loadIds(const std::vector<std::uint64_t> ids) override
{
last_modification = getLastModification();
const auto query = composeLoadIdsQuery(ids);
return new MySQLBlockInputStream{pool.Get(), query, sample_block, max_block_size};
}
bool isModified() const override { return getLastModification() > last_modification; }
bool supportsSelectiveLoad() const override { return true; }
DictionarySourcePtr clone() const override { return std::make_unique<MySQLDictionarySource>(*this); }
private:
mysqlxx::DateTime getLastModification() const
{
const auto Update_time_idx = 12;
mysqlxx::DateTime update_time{std::time(nullptr)};
try
{
auto connection = pool.Get();
auto query = connection->query("SHOW TABLE STATUS LIKE '%" + strconvert::escaped_for_like(table) + "%';");
auto result = query.use();
if (auto row = result.fetch())
{
const auto & update_time_value = row[Update_time_idx];
if (!update_time_value.isNull())
update_time = update_time_value.getDateTime();
/// fetch remaining rows to avoid "commands out of sync" error
while (auto row = result.fetch());
}
}
catch (...)
{
tryLogCurrentException("MySQLDictionarySource");
}
/// we suppose failure to get modification time is not an error, therefore return current time
return update_time;
}
static std::string composeLoadAllQuery(const Block & block, const std::string & table)
{
std::string query;
{
WriteBufferFromString out{query};
writeString("SELECT ", out);
auto first = true;
for (const auto idx : ext::range(0, block.columns()))
{
if (!first)
writeString(", ", out);
writeString(block.getByPosition(idx).name, out);
first = false;
}
writeString(" FROM ", out);
writeProbablyBackQuotedString(table, out);
writeChar(';', out);
}
return query;
}
std::string composeLoadIdsQuery(const std::vector<std::uint64_t> ids)
{
std::string query;
{
WriteBufferFromString out{query};
writeString("SELECT ", out);
auto first = true;
for (const auto idx : ext::range(0, sample_block.columns()))
{
if (!first)
writeString(", ", out);
writeString(sample_block.getByPosition(idx).name, out);
first = false;
}
const auto & id_column_name = sample_block.getByPosition(0).name;
writeString(" FROM ", out);
writeProbablyBackQuotedString(table, out);
writeString(" WHERE ", out);
writeProbablyBackQuotedString(id_column_name, out);
writeString(" IN (", out);
first = true;
for (const auto id : ids)
{
if (!first)
writeString(", ", out);
first = false;
writeString(toString(id), out);
}
writeString(");", out);
}
return query;
}
const std::string table;
Block sample_block;
mutable mysqlxx::PoolWithFailover pool;
const std::string load_all_query;
mysqlxx::DateTime last_modification;
};
}