diff --git a/lib/impure/db_mysql.nim b/lib/impure/db_mysql.nim
index 6284b7995..118ed39bb 100755
--- a/lib/impure/db_mysql.nim
+++ b/lib/impure/db_mysql.nim
@@ -18,7 +18,11 @@ type
   EDb* = object of EIO ## exception that is raised if a database error occurs
 
   TSqlQuery* = distinct string ## an SQL query string
- 
+
+  FDb* = object of FIO ## effect that denotes a database operation
+  FReadDb* = object of FReadIO   ## effect that denotes a read operation
+  FWriteDb* = object of FWriteIO ## effect that denotes a write operation
+
 proc dbError(db: TDbConn) {.noreturn.} = 
   ## raises an EDb exception.
   var e: ref EDb
@@ -60,12 +64,18 @@ proc dbFormat(formatstr: TSqlQuery, args: varargs[string]): string =
     else: 
       add(result, c)
   
-proc TryExec*(db: TDbConn, query: TSqlQuery, args: varargs[string, `$`]): bool =
+proc TryExec*(db: TDbConn, query: TSqlQuery, args: varargs[string, `$`]): bool {.
+  tags: [FReadDB, FWriteDb].} =
   ## tries to execute the query and returns true if successful, false otherwise.
   var q = dbFormat(query, args)
   return mysql.RealQuery(db, q, q.len) == 0'i32
 
-proc Exec*(db: TDbConn, query: TSqlQuery, args: varargs[string, `$`]) =
+proc rawExec(db: TDbConn, query: TSqlQuery, args: varargs[string, `$`]) =
+  var q = dbFormat(query, args)
+  if mysql.RealQuery(db, q, q.len) != 0'i32: dbError(db)
+
+proc Exec*(db: TDbConn, query: TSqlQuery, args: varargs[string, `$`]) {.
+  tags: [FReadDB, FWriteDb].} =
   ## executes the query and raises EDB if not successful.
   var q = dbFormat(query, args)
   if mysql.RealQuery(db, q, q.len) != 0'i32: dbError(db)
@@ -80,11 +90,11 @@ proc properFreeResult(sqlres: mysql.PRES, row: cstringArray) =
   mysql.FreeResult(sqlres)
   
 iterator FastRows*(db: TDbConn, query: TSqlQuery,
-                   args: varargs[string, `$`]): TRow =
+                   args: varargs[string, `$`]): TRow {.tags: [FReadDB].} =
   ## executes the query and iterates over the result dataset. This is very 
   ## fast, but potenially dangerous: If the for-loop-body executes another
   ## query, the results can be undefined. For MySQL this is the case!.
-  Exec(db, query, args)
+  rawExec(db, query, args)
   var sqlres = mysql.UseResult(db)
   if sqlres != nil:
     var L = int(mysql.NumFields(sqlres))
@@ -100,9 +110,9 @@ iterator FastRows*(db: TDbConn, query: TSqlQuery,
     properFreeResult(sqlres, row)
 
 proc getRow*(db: TDbConn, query: TSqlQuery,
-             args: varargs[string, `$`]): TRow =
+             args: varargs[string, `$`]): TRow {.tags: [FReadDB].} =
   ## retrieves a single row.
-  Exec(db, query, args)
+  rawExec(db, query, args)
   var sqlres = mysql.UseResult(db)
   if sqlres != nil:
     var L = int(mysql.NumFields(sqlres))
@@ -115,10 +125,10 @@ proc getRow*(db: TDbConn, query: TSqlQuery,
     properFreeResult(sqlres, row)
 
 proc GetAllRows*(db: TDbConn, query: TSqlQuery, 
-                 args: varargs[string, `$`]): seq[TRow] =
+                 args: varargs[string, `$`]): seq[TRow] {.tags: [FReadDB].} =
   ## executes the query and returns the whole result dataset.
   result = @[]
-  Exec(db, query, args)
+  rawExec(db, query, args)
   var sqlres = mysql.UseResult(db)
   if sqlres != nil:
     var L = int(mysql.NumFields(sqlres))
@@ -134,12 +144,12 @@ proc GetAllRows*(db: TDbConn, query: TSqlQuery,
     mysql.FreeResult(sqlres)
 
 iterator Rows*(db: TDbConn, query: TSqlQuery, 
-               args: varargs[string, `$`]): TRow =
+               args: varargs[string, `$`]): TRow {.tags: [FReadDB].} =
   ## same as `FastRows`, but slower and safe.
   for r in items(GetAllRows(db, query, args)): yield r
 
 proc GetValue*(db: TDbConn, query: TSqlQuery, 
-               args: varargs[string, `$`]): string = 
+               args: varargs[string, `$`]): string {.tags: [FReadDB].} = 
   ## executes the query and returns the result dataset's the first column 
   ## of the first row. Returns "" if the dataset contains no rows. This uses
   ## `FastRows`, so it inherits its fragile behaviour.
@@ -149,7 +159,7 @@ proc GetValue*(db: TDbConn, query: TSqlQuery,
     break
 
 proc TryInsertID*(db: TDbConn, query: TSqlQuery, 
-                  args: varargs[string, `$`]): int64 =
+                  args: varargs[string, `$`]): int64 {.tags: [FWriteDb].} =
   ## executes the query (typically "INSERT") and returns the 
   ## generated ID for the row or -1 in case of an error.
   var q = dbFormat(query, args)
@@ -159,24 +169,26 @@ proc TryInsertID*(db: TDbConn, query: TSqlQuery,
     result = mysql.InsertId(db)
   
 proc InsertID*(db: TDbConn, query: TSqlQuery, 
-               args: varargs[string, `$`]): int64 = 
+               args: varargs[string, `$`]): int64 {.tags: [FWriteDb].} = 
   ## executes the query (typically "INSERT") and returns the 
   ## generated ID for the row.
   result = TryInsertID(db, query, args)
   if result < 0: dbError(db)
 
 proc ExecAffectedRows*(db: TDbConn, query: TSqlQuery, 
-                       args: varargs[string, `$`]): int64 = 
+                       args: varargs[string, `$`]): int64 {.
+                       tags: [FReadDB, FWriteDb].} = 
   ## runs the query (typically "UPDATE") and returns the
   ## number of affected rows
-  Exec(db, query, args)
+  rawExec(db, query, args)
   result = mysql.AffectedRows(db)
 
-proc Close*(db: TDbConn) = 
+proc Close*(db: TDbConn) {.tags: [FDb].} = 
   ## closes the database connection.
   if db != nil: mysql.Close(db)
 
-proc Open*(connection, user, password, database: string): TDbConn =
+proc Open*(connection, user, password, database: string): TDbConn {.
+  tags: [FDb].} =
   ## opens a database connection. Raises `EDb` if the connection could not
   ## be established.
   result = mysql.Init(nil)