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Use a specialised count query for browsing tables/views

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For queries built from a table and filters, use a specialised count query
that only takes into account the where part of the statement. This will
speed-up the Browse Data tab for big tables.

See issue #1666
This commit is contained in:
mgrojo
2018-12-19 23:58:30 +01:00
committed by Martin Kleusberg
parent b4667b6bac
commit cfdf68d562
6 changed files with 47 additions and 28 deletions
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16
src/RowLoader.cpp
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@@ -26,6 +26,7 @@ RowLoader::RowLoader (
: db_getter(db_getter_), statement_logger(statement_logger_), headers(headers_)
, cache_mutex(cache_mutex_), cache_data(cache_data_)
, query()
, countQuery()
, num_tasks(0)
, pDb(nullptr)
, stop_requested(false)
@@ -34,10 +35,15 @@ RowLoader::RowLoader (
{
}
void RowLoader::setQuery (QString new_query)
void RowLoader::setQuery (QString new_query, QString newCountQuery)
{
std::lock_guard<std::mutex> lk(m);
query = new_query;
if (newCountQuery.isEmpty())
// If it is a normal query - hopefully starting with SELECT - just do a COUNT on it and return the results
countQuery = QString("SELECT COUNT(*) FROM (%1);").arg(rtrimChar(query, ';'));
else
countQuery = newCountQuery;
}
void RowLoader::triggerRowCountDetermination(int token)
@@ -89,10 +95,8 @@ int RowLoader::countRows()
return retval;
}
} else {
// If it is a normal query - hopefully starting with SELECT - just do a COUNT on it and return the results
QString sCountQuery = QString("SELECT COUNT(*) FROM (%1);").arg(rtrimChar(query, ';'));
statement_logger(sCountQuery);
QByteArray utf8Query = sCountQuery.toUtf8();
statement_logger(countQuery);
QByteArray utf8Query = countQuery.toUtf8();
sqlite3_stmt* stmt;
int status = sqlite3_prepare_v2(pDb.get(), utf8Query, utf8Query.size(), &stmt, nullptr);
@@ -106,7 +110,7 @@ int RowLoader::countRows()
}
sqlite3_finalize(stmt);
} else {
qWarning() << "Count query failed: " << sCountQuery;
qWarning() << "Count query failed: " << countQuery;
}
}