We use only one global connection to the database

include/cache.h

@@ -1,14 +1,149 @@
 #pragma once
-#include "merrors.h"
+#include "GPL.h"
+#include <functional>
 #include <libpq-fe.h>
 #include <sqlite3.h>
 #include <time.h>
 #include <variant>
 
+using michlib::GPL;
 using michlib::int_cast;
 using michlib::MString;
 using michlib::pointer_cast;
 
+class SQLiteConnection
+{
+ public:
+ using DBType   = sqlite3*;
+ using FuncType = std::function<void(DBType)>;
+
+ private:
+ static DBType                db;
+ static size_t                count;
+ static std::vector<FuncType> destructs;
+
+ public:
+ SQLiteConnection()
+ {
+  count++;
+  if(db == nullptr)
+  {
+   MString oldprefix = GPL.UsePrefix("SQLITE");
+   MString name      = GPL.ParameterSValue("db", "");
+   GPL.UsePrefix(oldprefix);
+
+   auto ret = sqlite3_open(name.Buf(), &db);
+   if(ret != SQLITE_OK)
+   {
+    sqlite3_close(db);
+    db = nullptr;
+   }
+  }
+ }
+
+ SQLiteConnection([[maybe_unused]] const SQLiteConnection& sq): SQLiteConnection() {}
+ SQLiteConnection(SQLiteConnection&&) = default;
+
+ SQLiteConnection& operator=([[maybe_unused]] const SQLiteConnection& sq)
+ {
+  *this = {};
+  return *this;
+ }
+ SQLiteConnection& operator=(SQLiteConnection&&) = default;
+
+ ~SQLiteConnection()
+ {
+  if(count == 0) michlib::errmessage("Destructor of SQLiteConnection called on count==0");
+  if(count > 1)
+   count--;
+  else
+  {
+   count = 0;
+   if(db != nullptr)
+   {
+    for(const auto& f: destructs) f(db);
+    sqlite3_close(db);
+   }
+   db = nullptr;
+  }
+ }
+
+ static void AddDestructor(FuncType&& f) { destructs.emplace_back(std::move(f)); }
+
+ operator DBType() const { return db; }
+
+ static DBType GetDB() { return db; }
+
+ explicit operator bool() const { return db != nullptr; }
+};
+
+class PostgreSQLConnection
+{
+ public:
+ using DBType   = PGconn*;
+ using FuncType = std::function<void(DBType)>;
+
+ private:
+ static DBType                conn;
+ static size_t                count;
+ static std::vector<FuncType> destructs;
+
+ public:
+ PostgreSQLConnection()
+ {
+  count++;
+  if(conn == nullptr)
+  {
+   MString oldprefix = GPL.UsePrefix("POSTGRES");
+   MString name      = GPL.ParameterSValue("connection", "");
+   GPL.UsePrefix(oldprefix);
+
+   conn = PQconnectdb(name.Buf());
+   if(PQstatus(conn) != CONNECTION_OK)
+   {
+    michlib::errmessage(PQerrorMessage(conn));
+    PQfinish(conn);
+    conn = nullptr;
+   }
+  }
+ }
+
+ PostgreSQLConnection([[maybe_unused]] const PostgreSQLConnection& pq): PostgreSQLConnection() {}
+ PostgreSQLConnection(PostgreSQLConnection&&) = default;
+
+ PostgreSQLConnection& operator=([[maybe_unused]] const PostgreSQLConnection& pq)
+ {
+  *this = {};
+  return *this;
+ }
+ PostgreSQLConnection& operator=(PostgreSQLConnection&&) = default;
+
+ ~PostgreSQLConnection()
+ {
+  if(count == 0) michlib::errmessage("Destructor of PostgreSQLConnection called on count==0");
+  if(count > 1)
+   count--;
+  else
+  {
+   count = 0;
+   if(conn != nullptr)
+   {
+    for(const auto& f: destructs) f(conn);
+    PQfinish(conn);
+   }
+   conn = nullptr;
+  }
+ }
+
+ static void AddDestructor(FuncType&& f) { destructs.emplace_back(std::move(f)); }
+
+ operator DBType() const { return conn; }
+
+ static DBType GetDB() { return conn; }
+
+ explicit operator bool() const { return conn != nullptr; }
+};
+
 class GenericCache
 {
  public:
@@ -27,18 +162,17 @@ class FakeCache: public GenericCache
 
 class SQLiteCache: public GenericCache
 {
- sqlite3* db = nullptr;
+ static bool regdest;
+
+ SQLiteConnection db;
 
  public:
- bool Init(const MString& name)
+ bool Init()
  {
-  Close();
-  auto ret = sqlite3_open(name.Buf(), &db);
-  if(ret != SQLITE_OK)
+  if(!db) return false;
+
+  if(!regdest)
   {
-   Close();
-   return false;
-  }
    // Create table
    sqlite3_stmt* sqst;
    int           i;
@@ -51,18 +185,25 @@ class SQLiteCache: public GenericCache
    if(i != SQLITE_DONE)
    {
     sqlite3_finalize(sqst);
-   Close();
     return false;
    }
    sqlite3_finalize(sqst);
    sqlite3_busy_timeout(db, 1000);
-  return true;
- }
 
- void Close()
+   db.AddDestructor(
+       [](SQLiteConnection::DBType db)
        {
-  if(db != nullptr) sqlite3_close(db);
-  db = nullptr;
+        sqlite3_stmt* sqst = nullptr;
+        int           i    = SQLITE_OK;
+
+        if(i == SQLITE_OK) i = sqlite3_prepare_v2(db, "DELETE from `cache` WHERE exptime<?1;", -1, &sqst, 0);
+        if(i == SQLITE_OK) i = sqlite3_bind_int64(sqst, 1, time(nullptr));
+        if(i == SQLITE_OK) i = sqlite3_step(sqst);
+        sqlite3_finalize(sqst);
+       });
+   regdest = true;
+  }
+  return true;
  }
 
  virtual bool Put(const MString& key, const MString& value, size_t ttl) const override
@@ -107,26 +248,16 @@ class SQLiteCache: public GenericCache
   return {"", false};
  }
 
- virtual ~SQLiteCache() override
- {
-  if(!*this) return;
-
-  sqlite3_stmt* sqst = nullptr;
-  int           i    = SQLITE_OK;
-
-  if(i == SQLITE_OK) i = sqlite3_prepare_v2(db, "DELETE from `cache` WHERE exptime<?1;", -1, &sqst, 0);
-  if(i == SQLITE_OK) i = sqlite3_bind_int64(sqst, 1, time(nullptr));
-  if(i == SQLITE_OK) i = sqlite3_step(sqst);
-  sqlite3_finalize(sqst);
-  sqlite3_close_v2(db);
- }
+ virtual ~SQLiteCache() override = default;
 
  explicit operator bool() const { return db != nullptr; }
 };
 
 class PostgreSQLCache: public GenericCache
 {
- PGconn* conn = nullptr;
+ static bool regdest;
+
+ PostgreSQLConnection conn;
 
  bool CheckCon() const
  {
@@ -148,18 +279,12 @@ class PostgreSQLCache: public GenericCache
  }
 
  public:
- bool Init(const MString& name)
+ bool Init()
  {
-  Close();
-  conn = PQconnectdb(name.Buf());
+  if(!conn) return false;
 
-  if(PQstatus(conn) != CONNECTION_OK)
+  if(!regdest)
   {
-   michlib::errmessage(PQerrorMessage(conn));
-   Close();
-   return false;
-  }
-
    // Create table
    if(false)
    {
@@ -169,18 +294,21 @@ class PostgreSQLCache: public GenericCache
      michlib::errmessage(PQresStatus(PQresultStatus(res)));
      michlib::errmessage(PQerrorMessage(conn));
      PQclear(res);
-    Close();
     }
     else
      PQclear(res);
    }
-  return true;
- }
 
- void Close()
+   conn.AddDestructor(
+       [](PostgreSQLConnection::DBType conn)
        {
-  if(conn != nullptr) PQfinish(conn);
-  conn = nullptr;
+        auto* res = PQexec(conn, "DELETE FROM cache WHERE exptime<localtimestamp;");
+        PQclear(res);
+       });
+
+   regdest = true;
+  }
+  return true;
  }
 
  virtual bool Put(const MString& key, const MString& value, size_t ttl) const override
@@ -235,14 +363,7 @@ class PostgreSQLCache: public GenericCache
   return {std::move(val), true};
  }
 
- virtual ~PostgreSQLCache() override
- {
-  if(!CheckCon()) return;
-
-  auto* res = PQexec(conn, "DELETE FROM cache WHERE exptime<localtimestamp;");
-  PQclear(res);
-  Close();
- }
+ virtual ~PostgreSQLCache() override = default;
 
  explicit operator bool() const { return conn != nullptr; }
 };
@@ -262,14 +383,14 @@ inline GenericCache* CreateCache(const MString& cachedesc)
  if(name == "sqlite")
  {
   auto ret = new SQLiteCache;
-  ret->Init(par);
+  ret->Init();
   if(*ret) return ret;
   delete ret;
  }
  if(name == "postgre" || name == "postgres" || name == "postgresql")
  {
   auto ret = new PostgreSQLCache;
-  ret->Init(par);
+  ret->Init();
   if(*ret) return ret;
   delete ret;
  }

src/cache.cpp

@@ -0,0 +1,14 @@
+#define MICHLIB_NOSOURCE
+#include "cache.h"
+
+SQLiteConnection::DBType                SQLiteConnection::db        = nullptr;
+size_t                                  SQLiteConnection::count     = 0;
+std::vector<SQLiteConnection::FuncType> SQLiteConnection::destructs = {};
+
+PostgreSQLConnection::DBType                PostgreSQLConnection::conn      = nullptr;
+size_t                                      PostgreSQLConnection::count     = 0;
+std::vector<PostgreSQLConnection::FuncType> PostgreSQLConnection::destructs = {};
+
+bool SQLiteCache::regdest = false;
+
+bool PostgreSQLCache::regdest = false;