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cache.cpp
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cache.cpp
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#include "cache.h"
#include "common.h"
#include <QDir>
#include <QSqlDatabase>
#include <QSqlError>
#include <QSqlQuery>
#include <QStringLiteral>
#include <QVariant>
#include <QtSql/qsqldatabase.h>
#include <QtSql/qsqlquery.h>
#include <fmt/format.h>
namespace {
constexpr char const *CACHE_DIR = ".local/share/elekter";
constexpr char const *DB_NAME = "nordpool.db";
constexpr char const *CREATE_TABLES[] = {
R"(CREATE TABLE IF NOT EXISTS blocks (
id INTEGER PRIMARY KEY,
region CHAR(2) NOT NULL,
start_h INTEGER NOT NULL,
size INTEGER NOT NULL))",
"CREATE UNIQUE INDEX IF NOT EXISTS idx_blocks ON blocks (region, start_h)",
R"(CREATE TABLE IF NOT EXISTS prices (
block_id INTEGER NOT NULL,
time_h INTEGER NOT NULL,
price DOUBLE NOT NULL))",
"CREATE UNIQUE INDEX IF NOT EXISTS idx_price_blocks ON prices (block_id, time_h)",
nullptr
};
constexpr char const *INSERT_BLOCK = "INSERT INTO blocks (region, start_h, size) VALUES (?,?,?)";
constexpr char const *INSERT_PRICE = "INSERT INTO prices (block_id, time_h, price) VALUES (?,?,?)";
constexpr char const *GET_PRICE_BLOCKS =
R"(SELECT id, start_h, size FROM blocks
WHERE region = :region AND
(start_h >= :start OR (start_h + size) > :start) AND
(start_h <= :end))";
constexpr char const *GET_PRICES =
R"(SELECT time_h, price FROM prices
WHERE block_id=:block_id AND time_h >= :start AND time_h <= :end)";
class Transaction {
public:
inline Transaction(QSqlDatabase &db)
: _db(&db)
{
_db->transaction();
}
inline ~Transaction()
{
if (_db)
_db->rollback();
}
inline bool commit()
{
auto rval = _db->commit();
if (rval)
_db = nullptr;
return rval;
}
private:
QSqlDatabase *_db = nullptr;
};
} // namespace
namespace El {
// -----------------------------------------------------------------------------
Cache::Cache(App const &app, QObject *parent)
: QObject(parent)
, _app(app)
{
// create the cache directory
auto const home = QDir::home();
if (!home.mkpath(CACHE_DIR)) {
fmt::print(stderr, "Vahemälu kausta {} loomine ebaõnnestus\n", CACHE_DIR);
return;
}
// initialize the database
if (!init_database()) {
return;
}
_valid = true;
}
Cache::~Cache() = default;
bool Cache::init_database()
{
auto db = QSqlDatabase::addDatabase("QSQLITE");
// open the database
auto const db_name = QString{"%1/%2/%3"}.arg(QDir::homePath(), CACHE_DIR, DB_NAME);
db.setDatabaseName(db_name);
if (!db.open()) {
fmt::print(stderr, "Vahemälu andmebaasi faili {} avamine ebaõnnestus: {}\n", db_name, db.lastError().text());
return false;
}
// create tables
QSqlQuery q{db};
auto sql = CREATE_TABLES;
for (; *sql; ++sql) {
if (!q.prepare(*sql)) {
fmt::print(stderr, "Päringu {} ettevalmistamine ebaõnnestus: {}\n", q.lastQuery(), q.lastError().text());
return false;
}
if (!q.exec()) {
fmt::print(stderr, "Päringu {} käivitamine ebaõnnestus: {}\n", q.lastQuery(), q.lastError().text());
return false;
}
}
return true;
}
auto Cache::get_prices(QString const ®ion, int start_h, int end_h) const -> PriceBlocks const
{
auto db = QSqlDatabase::database();
if (!db.isOpen()) {
throw Exception{"andmebaas ei ole avatud"};
}
// prepare SQL statements
QSqlQuery q_blocks{db};
if (!q_blocks.prepare(GET_PRICE_BLOCKS)) {
throw Exception{"päringu {} ettevalmistamine ebaõnnestus: {}", q_blocks.lastQuery(), q_blocks.lastError().text()};
}
q_blocks.bindValue(":region", region);
q_blocks.bindValue(":start", QVariant{start_h});
q_blocks.bindValue(":end", QVariant{end_h});
QSqlQuery q_prices{db};
if (!q_prices.prepare(GET_PRICES)) {
throw Exception{"päringu {} ettevalmistamine ebaõnnestus: {}", q_prices.lastQuery(), q_prices.lastError().text()};
}
q_prices.bindValue(":start", QVariant{start_h});
q_prices.bindValue(":end", QVariant{end_h});
if (!q_blocks.exec()) {
throw Exception{"päringu {} käivitamine ebaõnnestus: {}", q_blocks.lastQuery(), q_blocks.lastError().text()};
}
// we now have zero, one or multiple price blocks
PriceBlocks blocks{};
while (q_blocks.next()) {
// load all the prices from this block that are within the request time frame
q_prices.bindValue(":block_id", q_blocks.value(0).toLongLong());
if (!q_prices.exec()) {
throw Exception{"päringu {} käivitamine ebaõnnestus: {}", q_prices.lastQuery(), q_prices.lastError().text()};
}
// now we have price records
PriceBlock block{};
while (q_prices.next()) {
block.append({q_prices.value(0).toInt(), q_prices.value(1).toDouble()});
}
if (!block.empty()) {
blocks.append(std::move(block));
}
}
return blocks;
}
void Cache::store_prices(QString const ®ion, PriceBlocks const &prices)
{
auto db = QSqlDatabase::database();
if (!db.isOpen()) {
throw Exception{"andmebaas ei ole avatud"};
}
// prepare SQL statements
QSqlQuery q_block{db};
if (!q_block.prepare(INSERT_BLOCK)) {
throw Exception{"päringu {} ettevalmistamine ebaõnnestus: {}", q_block.lastQuery(), q_block.lastError().text()};
}
q_block.bindValue(0, region);
QSqlQuery q_price{db};
if (!q_price.prepare(INSERT_PRICE)) {
throw Exception{"päringu {} ettevalmistamine ebaõnnestus: {}", q_price.lastQuery(), q_price.lastError().text()};
}
Transaction tr{db};
// store all the blocks and prices
for (auto const &b : prices.blocks()) {
auto time_h = b.start_time_h;
q_block.bindValue(1, QVariant{b.start_time_h});
q_block.bindValue(2, QVariant{b.size()});
if (!q_block.exec()) {
throw Exception{"päringu {} käivitamine ebaõnnestus: {}", q_block.lastQuery(), q_block.lastError().text()};
}
q_price.bindValue(0, q_block.lastInsertId());
for (auto const price : b.prices) {
q_price.bindValue(1, QVariant{time_h++});
q_price.bindValue(2, QVariant{price});
if (!q_price.exec()) {
throw Exception{"päringu {} käivitamine ebaõnnestus: {}", q_price.lastQuery(), q_price.lastError().text()};
}
}
}
if (!tr.commit()) {
throw Exception{"andmebaasi salvestamine ebaõnnestus: {}", db.lastError().text()};
}
}
} // namespace El