// Copyright 2011 Google Inc.
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above copyright
// notice, this list of conditions and the following disclaimer in the
// documentation and/or other materials provided with the distribution.
// * Neither the name of Google Inc. nor the names of its contributors
// may be used to endorse or promote products derived from this software
// without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
/// Fetches an integer column from a statement of the 'metadata' table.
///
/// \param stmt The statement from which to get the column value.
/// \param column The name of the column to retrieve.
///
/// \return The value of the column.
///
/// \throw store::integrity_error If there is a problem fetching the value
/// caused by an invalid schema or data.
static int64_t
int64_column(sqlite::statement& stmt, const char* column)
{
int index;
try {
index = stmt.column_id(column);
} catch (const sqlite::invalid_column_error& e) {
UNREACHABLE_MSG("Invalid column specification; the SELECT statement "
"should have caught this");
}
if (stmt.column_type(index) != sqlite::type_integer)
throw store::integrity_error(F("The '%s' column in 'metadata' table "
"has an invalid type") % column);
return stmt.column_int64(index);
}
} // anonymous namespace
/// Constructs a new metadata object.
///
/// \param schema_version_ The schema version.
/// \param timestamp_ The time at which this version was created.
store::metadata::metadata(const int schema_version_, const int64_t timestamp_) :
_schema_version(schema_version_),
_timestamp(timestamp_)
{
}
/// Returns the timestamp of this entry.
///
/// \return The timestamp in this metadata entry.
int64_t
store::metadata::timestamp(void) const
{
return _timestamp;
}
/// Returns the schema version.
///
/// \return The schema version in this metadata entry.
int
store::metadata::schema_version(void) const
{
return _schema_version;
}
/// Reads the latest metadata entry from the database.
///
/// \param db The database from which to read the metadata from.
///
/// \return The current metadata of the database. It is not OK for the metadata
/// table to be empty, so this is guaranteed to return a value unless there is
/// an error.
///
/// \throw store::integrity_error If the metadata in the database is empty,
/// has an invalid schema or its contents are bogus.
store::metadata
store::metadata::fetch_latest(sqlite::database& db)
{
try {
sqlite::statement stmt = db.create_statement(
"SELECT schema_version, timestamp FROM metadata "
"ORDER BY schema_version DESC LIMIT 1");
if (!stmt.step())
throw store::integrity_error("The 'metadata' table is empty");
const int schema_version_ =
static_cast< int >(int64_column(stmt, "schema_version"));
const int64_t timestamp_ = int64_column(stmt, "timestamp");
if (stmt.step())
UNREACHABLE_MSG("Got more than one result from a query that "
"does not permit this; any pragmas defined?");
