big update for the db*.nim modules; uses new db_common.nim

4 files changed, 188 insertions, 143 deletions

diff --git a/lib/impure/db_mysql.nim b/lib/impure/db_mysql.nim
index 7f7511264..ca99636f6 100644
--- a/lib/impure/db_mysql.nim
+++ b/lib/impure/db_mysql.nim
@@ -1,7 +1,7 @@
 #
 #
 #            Nim's Runtime Library
-#        (c) Copyright 2012 Andreas Rumpf
+#        (c) Copyright 2015 Andreas Rumpf
 #
 #    See the file "copying.txt", included in this
 #    distribution, for details about the copyright.
@@ -43,6 +43,9 @@
 
 import strutils, mysql
 
+import db_common
+export db_common
+
 type
   DbConn* = PMySQL    ## encapsulates a database connection
   Row* = seq[string]   ## a row of a dataset. NULL database values will be
@@ -50,38 +53,15 @@ type
   InstantRow* = tuple[row: cstringArray, len: int]  ## a handle that can be
                                                     ## used to get a row's
                                                     ## column text on demand
-  EDb* = object of IOError ## exception that is raised if a database error occurs
-
-  SqlQuery* = distinct string ## an SQL query string
-
-  FDb* = object of IOEffect ## effect that denotes a database operation
-  FReadDb* = object of FDb   ## effect that denotes a read operation
-  FWriteDb* = object of FDb  ## effect that denotes a write operation
-{.deprecated: [TRow: Row, TSqlQuery: SqlQuery, TDbConn: DbConn].}
-
-proc sql*(query: string): SqlQuery {.noSideEffect, inline.} =
-  ## constructs a SqlQuery from the string `query`. This is supposed to be
-  ## used as a raw-string-literal modifier:
-  ## ``sql"update user set counter = counter + 1"``
-  ##
-  ## If assertions are turned off, it does nothing. If assertions are turned
-  ## on, later versions will check the string for valid syntax.
-  result = SqlQuery(query)
+{.deprecated: [TRow: Row, TDbConn: DbConn].}
 
-proc dbError(db: DbConn) {.noreturn.} =
-  ## raises an EDb exception.
-  var e: ref EDb
+proc dbError*(db: DbConn) {.noreturn.} =
+  ## raises a DbError exception.
+  var e: ref DbError
   new(e)
   e.msg = $mysql.error(db)
   raise e
 
-proc dbError*(msg: string) {.noreturn.} =
-  ## raises an EDb exception with message `msg`.
-  var e: ref EDb
-  new(e)
-  e.msg = msg
-  raise e
-
 when false:
   proc dbQueryOpt*(db: DbConn, query: string, args: varargs[string, `$`]) =
     var stmt = mysql_stmt_init(db)
@@ -114,7 +94,7 @@ proc dbFormat(formatstr: SqlQuery, args: varargs[string]): string =
       add(result, c)
 
 proc tryExec*(db: DbConn, query: SqlQuery, args: varargs[string, `$`]): bool {.
-  tags: [FReadDB, FWriteDb].} =
+  tags: [ReadDbEffect, WriteDbEffect].} =
   ## tries to execute the query and returns true if successful, false otherwise.
   var q = dbFormat(query, args)
   return mysql.realQuery(db, q, q.len) == 0'i32
@@ -124,7 +104,7 @@ proc rawExec(db: DbConn, query: SqlQuery, args: varargs[string, `$`]) =
   if mysql.realQuery(db, q, q.len) != 0'i32: dbError(db)
 
 proc exec*(db: DbConn, query: SqlQuery, args: varargs[string, `$`]) {.
-  tags: [FReadDB, FWriteDb].} =
+  tags: [ReadDbEffect, WriteDbEffect].} =
   ## 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)
@@ -139,7 +119,7 @@ proc properFreeResult(sqlres: mysql.PRES, row: cstringArray) =
   mysql.freeResult(sqlres)
 
 iterator fastRows*(db: DbConn, query: SqlQuery,
-                   args: varargs[string, `$`]): Row {.tags: [FReadDB].} =
+                   args: varargs[string, `$`]): Row {.tags: [ReadDbEffect].} =
   ## executes the query and iterates over the result dataset.
   ##
   ## This is very fast, but potentially dangerous.  Use this iterator only
@@ -167,9 +147,9 @@ iterator fastRows*(db: DbConn, query: SqlQuery,
 
 iterator instantRows*(db: DbConn, query: SqlQuery,
                       args: varargs[string, `$`]): InstantRow
-                      {.tags: [FReadDb].} =
-  ## same as fastRows but returns a handle that can be used to get column text
-  ## on demand using []. Returned handle is valid only within the interator body.
+                      {.tags: [ReadDbEffect].} =
+  ## Same as fastRows but returns a handle that can be used to get column text
+  ## on demand using []. Returned handle is valid only within the iterator body.
   rawExec(db, query, args)
   var sqlres = mysql.useResult(db)
   if sqlres != nil:
@@ -182,16 +162,16 @@ iterator instantRows*(db: DbConn, query: SqlQuery,
     properFreeResult(sqlres, row)
 
 proc `[]`*(row: InstantRow, col: int): string {.inline.} =
-  ## returns text for given column of the row
+  ## Returns text for given column of the row.
   $row.row[col]
 
 proc len*(row: InstantRow): int {.inline.} =
-  ## returns number of columns in the row
+  ## Returns number of columns in the row.
   row.len
 
 proc getRow*(db: DbConn, query: SqlQuery,
-             args: varargs[string, `$`]): Row {.tags: [FReadDB].} =
-  ## retrieves a single row. If the query doesn't return any rows, this proc
+             args: varargs[string, `$`]): Row {.tags: [ReadDbEffect].} =
+  ## Retrieves a single row. If the query doesn't return any rows, this proc
   ## will return a Row with empty strings for each column.
   rawExec(db, query, args)
   var sqlres = mysql.useResult(db)
@@ -209,7 +189,7 @@ proc getRow*(db: DbConn, query: SqlQuery,
     properFreeResult(sqlres, row)
 
 proc getAllRows*(db: DbConn, query: SqlQuery,
-                 args: varargs[string, `$`]): seq[Row] {.tags: [FReadDB].} =
+                 args: varargs[string, `$`]): seq[Row] {.tags: [ReadDbEffect].} =
   ## executes the query and returns the whole result dataset.
   result = @[]
   rawExec(db, query, args)
@@ -232,19 +212,19 @@ proc getAllRows*(db: DbConn, query: SqlQuery,
     mysql.freeResult(sqlres)
 
 iterator rows*(db: DbConn, query: SqlQuery,
-               args: varargs[string, `$`]): Row {.tags: [FReadDB].} =
+               args: varargs[string, `$`]): Row {.tags: [ReadDbEffect].} =
   ## same as `fastRows`, but slower and safe.
   for r in items(getAllRows(db, query, args)): yield r
 
 proc getValue*(db: DbConn, query: SqlQuery,
-               args: varargs[string, `$`]): string {.tags: [FReadDB].} =
+               args: varargs[string, `$`]): string {.tags: [ReadDbEffect].} =
   ## executes the query and returns the first column of the first row of the
   ## result dataset. Returns "" if the dataset contains no rows or the database
   ## value is NULL.
   result = getRow(db, query, args)[0]
 
 proc tryInsertId*(db: DbConn, query: SqlQuery,
-                  args: varargs[string, `$`]): int64 {.tags: [FWriteDb].} =
+                  args: varargs[string, `$`]): int64 {.tags: [WriteDbEffect].} =
   ## 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)
@@ -254,7 +234,7 @@ proc tryInsertId*(db: DbConn, query: SqlQuery,
     result = mysql.insertId(db)
 
 proc insertId*(db: DbConn, query: SqlQuery,
-               args: varargs[string, `$`]): int64 {.tags: [FWriteDb].} =
+               args: varargs[string, `$`]): int64 {.tags: [WriteDbEffect].} =
   ## executes the query (typically "INSERT") and returns the
   ## generated ID for the row.
   result = tryInsertID(db, query, args)
@@ -262,18 +242,18 @@ proc insertId*(db: DbConn, query: SqlQuery,
 
 proc execAffectedRows*(db: DbConn, query: SqlQuery,
                        args: varargs[string, `$`]): int64 {.
-                       tags: [FReadDB, FWriteDb].} =
+                       tags: [ReadDbEffect, WriteDbEffect].} =
   ## runs the query (typically "UPDATE") and returns the
   ## number of affected rows
   rawExec(db, query, args)
   result = mysql.affectedRows(db)
 
-proc close*(db: DbConn) {.tags: [FDb].} =
+proc close*(db: DbConn) {.tags: [DbEffect].} =
   ## closes the database connection.
   if db != nil: mysql.close(db)
 
 proc open*(connection, user, password, database: string): DbConn {.
-  tags: [FDb].} =
+  tags: [DbEffect].} =
   ## opens a database connection. Raises `EDb` if the connection could not
   ## be established.
   result = mysql.init(nil)
@@ -291,7 +271,7 @@ proc open*(connection, user, password, database: string): DbConn {.
     dbError(errmsg)
 
 proc setEncoding*(connection: DbConn, encoding: string): bool {.
-  tags: [FDb].} =
+  tags: [DbEffect].} =
   ## sets the encoding of a database connection, returns true for
   ## success, false for failure.
   result = mysql.set_character_set(connection, encoding) == 0
diff --git a/lib/impure/db_postgres.nim b/lib/impure/db_postgres.nim
index 5603d9686..802efb71f 100644
--- a/lib/impure/db_postgres.nim
+++ b/lib/impure/db_postgres.nim
@@ -62,47 +62,28 @@
 ##             "Dominik")
 import strutils, postgres
 
+import db_common
+export db_common
+
 type
   DbConn* = PPGconn   ## encapsulates a database connection
   Row* = seq[string]  ## a row of a dataset. NULL database values will be
-                       ## transformed always to the empty string.
+                      ## transformed always to the empty string.
   InstantRow* = tuple[res: PPGresult, line: int32]  ## a handle that can be
                                                     ## used to get a row's
                                                     ## column text on demand
-  EDb* = object of IOError ## exception that is raised if a database error occurs
-
-  SqlQuery* = distinct string ## an SQL query string
   SqlPrepared* = distinct string ## a identifier for the prepared queries
 
-  FDb* = object of IOEffect ## effect that denotes a database operation
-  FReadDb* = object of FDb   ## effect that denotes a read operation
-  FWriteDb* = object of FDb  ## effect that denotes a write operation
-{.deprecated: [TRow: Row, TSqlQuery: SqlQuery, TDbConn: DbConn,
+{.deprecated: [TRow: Row, TDbConn: DbConn,
               TSqlPrepared: SqlPrepared].}
 
-proc sql*(query: string): SqlQuery {.noSideEffect, inline.} =
-  ## constructs a SqlQuery from the string `query`. This is supposed to be
-  ## used as a raw-string-literal modifier:
-  ## ``sql"update user set counter = counter + 1"``
-  ##
-  ## If assertions are turned off, it does nothing. If assertions are turned
-  ## on, later versions will check the string for valid syntax.
-  result = SqlQuery(query)
-
 proc dbError*(db: DbConn) {.noreturn.} =
-  ## raises an EDb exception.
-  var e: ref EDb
+  ## raises a DbError exception.
+  var e: ref DbError
   new(e)
   e.msg = $pqErrorMessage(db)
   raise e
 
-proc dbError*(msg: string) {.noreturn.} =
-  ## raises an EDb exception with message `msg`.
-  var e: ref EDb
-  new(e)
-  e.msg = msg
-  raise e
-
 proc dbQuote*(s: string): string =
   ## DB quotes the string.
   result = "'"
@@ -127,7 +108,7 @@ proc dbFormat(formatstr: SqlQuery, args: varargs[string]): string =
       add(result, c)
 
 proc tryExec*(db: DbConn, query: SqlQuery,
-              args: varargs[string, `$`]): bool {.tags: [FReadDB, FWriteDb].} =
+              args: varargs[string, `$`]): bool {.tags: [ReadDbEffect, WriteDbEffect].} =
   ## tries to execute the query and returns true if successful, false otherwise.
   var res = pqexecParams(db, dbFormat(query, args), 0, nil, nil,
                         nil, nil, 0)
@@ -135,7 +116,8 @@ proc tryExec*(db: DbConn, query: SqlQuery,
   pqclear(res)
 
 proc tryExec*(db: DbConn, stmtName: SqlPrepared,
-              args: varargs[string, `$`]): bool {.tags: [FReadDB, FWriteDb].} =
+              args: varargs[string, `$`]): bool {.tags: [
+              ReadDbEffect, WriteDbEffect].} =
   ## tries to execute the query and returns true if successful, false otherwise.
   var arr = allocCStringArray(args)
   var res = pqexecPrepared(db, stmtName.string, int32(args.len), arr,
@@ -145,7 +127,7 @@ proc tryExec*(db: DbConn, stmtName: SqlPrepared,
   pqclear(res)
 
 proc exec*(db: DbConn, query: SqlQuery, args: varargs[string, `$`]) {.
-  tags: [FReadDB, FWriteDb].} =
+  tags: [ReadDbEffect, WriteDbEffect].} =
   ## executes the query and raises EDB if not successful.
   var res = pqexecParams(db, dbFormat(query, args), 0, nil, nil,
                         nil, nil, 0)
@@ -153,7 +135,7 @@ proc exec*(db: DbConn, query: SqlQuery, args: varargs[string, `$`]) {.
   pqclear(res)
 
 proc exec*(db: DbConn, stmtName: SqlPrepared,
-          args: varargs[string]) {.tags: [FReadDB, FWriteDb].} =
+          args: varargs[string]) {.tags: [ReadDbEffect, WriteDbEffect].} =
   var arr = allocCStringArray(args)
   var res = pqexecPrepared(db, stmtName.string, int32(args.len), arr,
                            nil, nil, 0)
@@ -196,7 +178,7 @@ proc setRow(res: PPGresult, r: var Row, line, cols: int32) =
       add(r[col], x)
 
 iterator fastRows*(db: DbConn, query: SqlQuery,
-                   args: varargs[string, `$`]): Row {.tags: [FReadDB].} =
+                   args: varargs[string, `$`]): Row {.tags: [ReadDbEffect].} =
   ## 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 Postgres it is safe though.
@@ -209,7 +191,7 @@ iterator fastRows*(db: DbConn, query: SqlQuery,
   pqclear(res)
 
 iterator fastRows*(db: DbConn, stmtName: SqlPrepared,
-                   args: varargs[string, `$`]): Row {.tags: [FReadDB].} =
+                   args: varargs[string, `$`]): Row {.tags: [ReadDbEffect].} =
   ## executes the prepared query and iterates over the result dataset.
   var res = setupQuery(db, stmtName, args)
   var L = pqNfields(res)
@@ -221,9 +203,9 @@ iterator fastRows*(db: DbConn, stmtName: SqlPrepared,
 
 iterator instantRows*(db: DbConn, query: SqlQuery,
                       args: varargs[string, `$`]): InstantRow
-                      {.tags: [FReadDb].} =
+                      {.tags: [ReadDbEffect].} =
   ## same as fastRows but returns a handle that can be used to get column text
-  ## on demand using []. Returned handle is valid only within interator body.
+  ## on demand using []. Returned handle is valid only within iterator body.
   var res = setupQuery(db, query, args)
   for i in 0..pqNtuples(res)-1:
     yield (res: res, line: i)
@@ -231,9 +213,9 @@ iterator instantRows*(db: DbConn, query: SqlQuery,
 
 iterator instantRows*(db: DbConn, stmtName: SqlPrepared,
                       args: varargs[string, `$`]): InstantRow
-                      {.tags: [FReadDb].} =
+                      {.tags: [ReadDbEffect].} =
   ## same as fastRows but returns a handle that can be used to get column text
-  ## on demand using []. Returned handle is valid only within interator body.
+  ## on demand using []. Returned handle is valid only within iterator body.
   var res = setupQuery(db, stmtName, args)
   for i in 0..pqNtuples(res)-1:
     yield (res: res, line: i)
@@ -248,7 +230,7 @@ proc len*(row: InstantRow): int32 {.inline.} =
   pqNfields(row.res)
 
 proc getRow*(db: DbConn, query: SqlQuery,
-             args: varargs[string, `$`]): Row {.tags: [FReadDB].} =
+             args: varargs[string, `$`]): Row {.tags: [ReadDbEffect].} =
   ## retrieves a single row. If the query doesn't return any rows, this proc
   ## will return a Row with empty strings for each column.
   var res = setupQuery(db, query, args)
@@ -258,7 +240,7 @@ proc getRow*(db: DbConn, query: SqlQuery,
   pqclear(res)
 
 proc getRow*(db: DbConn, stmtName: SqlPrepared,
-             args: varargs[string, `$`]): Row {.tags: [FReadDB].} =
+             args: varargs[string, `$`]): Row {.tags: [ReadDbEffect].} =
   var res = setupQuery(db, stmtName, args)
   var L = pqNfields(res)
   result = newRow(L)
@@ -266,31 +248,34 @@ proc getRow*(db: DbConn, stmtName: SqlPrepared,
   pqClear(res)
 
 proc getAllRows*(db: DbConn, query: SqlQuery,
-                 args: varargs[string, `$`]): seq[Row] {.tags: [FReadDB].} =
+                 args: varargs[string, `$`]): seq[Row] {.
+                 tags: [ReadDbEffect].} =
   ## executes the query and returns the whole result dataset.
   result = @[]
   for r in fastRows(db, query, args):
     result.add(r)
 
 proc getAllRows*(db: DbConn, stmtName: SqlPrepared,
-                 args: varargs[string, `$`]): seq[Row] {.tags: [FReadDB].} =
+                 args: varargs[string, `$`]): seq[Row] {.tags:
+                 [ReadDbEffect].} =
   ## executes the prepared query and returns the whole result dataset.
   result = @[]
   for r in fastRows(db, stmtName, args):
     result.add(r)
 
 iterator rows*(db: DbConn, query: SqlQuery,
-               args: varargs[string, `$`]): Row {.tags: [FReadDB].} =
+               args: varargs[string, `$`]): Row {.tags: [ReadDbEffect].} =
   ## same as `fastRows`, but slower and safe.
   for r in items(getAllRows(db, query, args)): yield r
 
 iterator rows*(db: DbConn, stmtName: SqlPrepared,
-               args: varargs[string, `$`]): Row {.tags: [FReadDB].} =
+               args: varargs[string, `$`]): Row {.tags: [ReadDbEffect].} =
   ## same as `fastRows`, but slower and safe.
   for r in items(getAllRows(db, stmtName, args)): yield r
 
 proc getValue*(db: DbConn, query: SqlQuery,
-               args: varargs[string, `$`]): string {.tags: [FReadDB].} =
+               args: varargs[string, `$`]): string {.
+               tags: [ReadDbEffect].} =
   ## executes the query and returns the first column of the first row of the
   ## result dataset. Returns "" if the dataset contains no rows or the database
   ## value is NULL.
@@ -298,7 +283,8 @@ proc getValue*(db: DbConn, query: SqlQuery,
   result = if isNil(x): "" else: $x
 
 proc tryInsertID*(db: DbConn, query: SqlQuery,
-                  args: varargs[string, `$`]): int64  {.tags: [FWriteDb].}=
+                  args: varargs[string, `$`]): int64 {.
+                  tags: [WriteDbEffect].}=
   ## executes the query (typically "INSERT") and returns the
   ## generated ID for the row or -1 in case of an error. For Postgre this adds
   ## ``RETURNING id`` to the query, so it only works if your primary key is
@@ -311,7 +297,8 @@ proc tryInsertID*(db: DbConn, query: SqlQuery,
     result = -1
 
 proc insertID*(db: DbConn, query: SqlQuery,
-               args: varargs[string, `$`]): int64 {.tags: [FWriteDb].} =
+               args: varargs[string, `$`]): int64 {.
+               tags: [WriteDbEffect].} =
   ## executes the query (typically "INSERT") and returns the
   ## generated ID for the row. For Postgre this adds
   ## ``RETURNING id`` to the query, so it only works if your primary key is
@@ -321,7 +308,7 @@ proc insertID*(db: DbConn, query: SqlQuery,
 
 proc execAffectedRows*(db: DbConn, query: SqlQuery,
                        args: varargs[string, `$`]): int64 {.tags: [
-                       FReadDB, FWriteDb].} =
+                       ReadDbEffect, WriteDbEffect].} =
   ## executes the query (typically "UPDATE") and returns the
   ## number of affected rows.
   var q = dbFormat(query, args)
@@ -332,7 +319,7 @@ proc execAffectedRows*(db: DbConn, query: SqlQuery,
 
 proc execAffectedRows*(db: DbConn, stmtName: SqlPrepared,
                        args: varargs[string, `$`]): int64 {.tags: [
-                       FReadDB, FWriteDb].} =
+                       ReadDbEffect, WriteDbEffect].} =
   ## executes the query (typically "UPDATE") and returns the
   ## number of affected rows.
   var arr = allocCStringArray(args)
@@ -343,12 +330,12 @@ proc execAffectedRows*(db: DbConn, stmtName: SqlPrepared,
   result = parseBiggestInt($pqcmdTuples(res))
   pqclear(res)
 
-proc close*(db: DbConn) {.tags: [FDb].} =
+proc close*(db: DbConn) {.tags: [DbEffect].} =
   ## closes the database connection.
   if db != nil: pqfinish(db)
 
 proc open*(connection, user, password, database: string): DbConn {.
-  tags: [FDb].} =
+  tags: [DbEffect].} =
   ## opens a database connection. Raises `EDb` if the connection could not
   ## be established.
   ##
@@ -370,7 +357,7 @@ proc open*(connection, user, password, database: string): DbConn {.
   if pqStatus(result) != CONNECTION_OK: dbError(result) # result = nil
 
 proc setEncoding*(connection: DbConn, encoding: string): bool {.
-  tags: [FDb].} =
+  tags: [DbEffect].} =
   ## sets the encoding of a database connection, returns true for
   ## success, false for failure.
   return pqsetClientEncoding(connection, encoding) == 0
diff --git a/lib/impure/db_sqlite.nim b/lib/impure/db_sqlite.nim
index 8366fdadc..90a2f8728 100644
--- a/lib/impure/db_sqlite.nim
+++ b/lib/impure/db_sqlite.nim
@@ -1,7 +1,7 @@
 #
 #
 #            Nim's Runtime Library
-#        (c) Copyright 2012 Andreas Rumpf
+#        (c) Copyright 2015 Andreas Rumpf
 #
 #    See the file "copying.txt", included in this
 #    distribution, for details about the copyright.
@@ -42,45 +42,26 @@
 
 import strutils, sqlite3
 
+import db_common
+export db_common
+
 type
   DbConn* = PSqlite3  ## encapsulates a database connection
   Row* = seq[string]  ## a row of a dataset. NULL database values will be
                        ## transformed always to the empty string.
   InstantRow* = Pstmt  ## a handle that can be used to get a row's column
                        ## text on demand
-  EDb* = object of IOError ## exception that is raised if a database error occurs
-
-  SqlQuery* = distinct string ## an SQL query string
-
-  FDb* = object of IOEffect ## effect that denotes a database operation
-  FReadDb* = object of FDb   ## effect that denotes a read operation
-  FWriteDb* = object of FDb  ## effect that denotes a write operation
-{.deprecated: [TRow: Row, TSqlQuery: SqlQuery, TDbConn: DbConn].}
-
-proc sql*(query: string): SqlQuery {.noSideEffect, inline.} =
-  ## constructs a SqlQuery from the string `query`. This is supposed to be
-  ## used as a raw-string-literal modifier:
-  ## ``sql"update user set counter = counter + 1"``
-  ##
-  ## If assertions are turned off, it does nothing. If assertions are turned
-  ## on, later versions will check the string for valid syntax.
-  result = SqlQuery(query)
+{.deprecated: [TRow: Row, TDbConn: DbConn].}
 
-proc dbError(db: DbConn) {.noreturn.} =
-  ## raises an EDb exception.
-  var e: ref EDb
+proc dbError*(db: DbConn) {.noreturn.} =
+  ## raises a DbError exception.
+  var e: ref DbError
   new(e)
   e.msg = $sqlite3.errmsg(db)
   raise e
 
-proc dbError*(msg: string) {.noreturn.} =
-  ## raises an EDb exception with message `msg`.
-  var e: ref EDb
-  new(e)
-  e.msg = msg
-  raise e
-
-proc dbQuote(s: string): string =
+proc dbQuote*(s: string): string =
+  ## DB quotes the string.
   if s.isNil: return "NULL"
   result = "'"
   for c in items(s):
@@ -99,7 +80,8 @@ proc dbFormat(formatstr: SqlQuery, args: varargs[string]): string =
       add(result, c)
 
 proc tryExec*(db: DbConn, query: SqlQuery,
-              args: varargs[string, `$`]): bool {.tags: [FReadDb, FWriteDb].} =
+              args: varargs[string, `$`]): bool {.
+              tags: [ReadDbEffect, WriteDbEffect].} =
   ## tries to execute the query and returns true if successful, false otherwise.
   var q = dbFormat(query, args)
   var stmt: sqlite3.Pstmt
@@ -108,8 +90,8 @@ proc tryExec*(db: DbConn, query: SqlQuery,
       result = finalize(stmt) == SQLITE_OK
 
 proc exec*(db: DbConn, query: SqlQuery, args: varargs[string, `$`])  {.
-  tags: [FReadDb, FWriteDb].} =
-  ## executes the query and raises EDB if not successful.
+  tags: [ReadDbEffect, WriteDbEffect].} =
+  ## executes the query and raises DbError if not successful.
   if not tryExec(db, query, args): dbError(db)
 
 proc newRow(L: int): Row =
@@ -129,14 +111,14 @@ proc setRow(stmt: Pstmt, r: var Row, cols: cint) =
     if not isNil(x): add(r[col], x)
 
 iterator fastRows*(db: DbConn, query: SqlQuery,
-                   args: varargs[string, `$`]): Row  {.tags: [FReadDb].} =
+                   args: varargs[string, `$`]): Row {.tags: [ReadDbEffect].} =
   ## Executes the query and iterates over the result dataset.
   ##
   ## This is very fast, but potentially dangerous.  Use this iterator only
   ## if you require **ALL** the rows.
   ##
   ## Breaking the fastRows() iterator during a loop will cause the next
-  ## database query to raise an [EDb] exception ``unable to close due to ...``.
+  ## database query to raise a DbError exception ``unable to close due to ...``.
   var stmt = setupQuery(db, query, args)
   var L = (column_count(stmt))
   var result = newRow(L)
@@ -147,9 +129,9 @@ iterator fastRows*(db: DbConn, query: SqlQuery,
 
 iterator instantRows*(db: DbConn, query: SqlQuery,
                       args: varargs[string, `$`]): InstantRow
-                      {.tags: [FReadDb].} =
+                      {.tags: [ReadDbEffect].} =
   ## same as fastRows but returns a handle that can be used to get column text
-  ## on demand using []. Returned handle is valid only within the interator body.
+  ## on demand using []. Returned handle is valid only within the iterator body.
   var stmt = setupQuery(db, query, args)
   while step(stmt) == SQLITE_ROW:
     yield stmt
@@ -164,7 +146,7 @@ proc len*(row: InstantRow): int32 {.inline.} =
   column_count(row)
 
 proc getRow*(db: DbConn, query: SqlQuery,
-             args: varargs[string, `$`]): Row {.tags: [FReadDb].} =
+             args: varargs[string, `$`]): Row {.tags: [ReadDbEffect].} =
   ## retrieves a single row. If the query doesn't return any rows, this proc
   ## will return a Row with empty strings for each column.
   var stmt = setupQuery(db, query, args)
@@ -175,19 +157,19 @@ proc getRow*(db: DbConn, query: SqlQuery,
   if finalize(stmt) != SQLITE_OK: dbError(db)
 
 proc getAllRows*(db: DbConn, query: SqlQuery,
-                 args: varargs[string, `$`]): seq[Row] {.tags: [FReadDb].} =
+                 args: varargs[string, `$`]): seq[Row] {.tags: [ReadDbEffect].} =
   ## executes the query and returns the whole result dataset.
   result = @[]
   for r in fastRows(db, query, args):
     result.add(r)
 
 iterator rows*(db: DbConn, query: SqlQuery,
-               args: varargs[string, `$`]): Row {.tags: [FReadDb].} =
+               args: varargs[string, `$`]): Row {.tags: [ReadDbEffect].} =
   ## same as `FastRows`, but slower and safe.
   for r in fastRows(db, query, args): yield r
 
 proc getValue*(db: DbConn, query: SqlQuery,
-               args: varargs[string, `$`]): string {.tags: [FReadDb].} =
+               args: varargs[string, `$`]): string {.tags: [ReadDbEffect].} =
   ## executes the query and returns the first column of the first row of the
   ## result dataset. Returns "" if the dataset contains no rows or the database
   ## value is NULL.
@@ -205,7 +187,7 @@ proc getValue*(db: DbConn, query: SqlQuery,
 
 proc tryInsertID*(db: DbConn, query: SqlQuery,
                   args: varargs[string, `$`]): int64
-                  {.tags: [FWriteDb], raises: [].} =
+                  {.tags: [WriteDbEffect], raises: [].} =
   ## 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)
@@ -218,7 +200,7 @@ proc tryInsertID*(db: DbConn, query: SqlQuery,
       result = -1
 
 proc insertID*(db: DbConn, query: SqlQuery,
-               args: varargs[string, `$`]): int64 {.tags: [FWriteDb].} =
+               args: varargs[string, `$`]): int64 {.tags: [WriteDbEffect].} =
   ## executes the query (typically "INSERT") and returns the
   ## generated ID for the row. For Postgre this adds
   ## ``RETURNING id`` to the query, so it only works if your primary key is
@@ -228,18 +210,18 @@ proc insertID*(db: DbConn, query: SqlQuery,
 
 proc execAffectedRows*(db: DbConn, query: SqlQuery,
                        args: varargs[string, `$`]): int64 {.
-                       tags: [FReadDb, FWriteDb].} =
+                       tags: [ReadDbEffect, WriteDbEffect].} =
   ## executes the query (typically "UPDATE") and returns the
   ## number of affected rows.
   exec(db, query, args)
   result = changes(db)
 
-proc close*(db: DbConn) {.tags: [FDb].} =
+proc close*(db: DbConn) {.tags: [DbEffect].} =
   ## closes the database connection.
   if sqlite3.close(db) != SQLITE_OK: dbError(db)
 
 proc open*(connection, user, password, database: string): DbConn {.
-  tags: [FDb].} =
+  tags: [DbEffect].} =
   ## opens a database connection. Raises `EDb` if the connection could not
   ## be established. Only the ``connection`` parameter is used for ``sqlite``.
   var db: DbConn
@@ -249,7 +231,7 @@ proc open*(connection, user, password, database: string): DbConn {.
     dbError(db)
 
 proc setEncoding*(connection: DbConn, encoding: string): bool {.
-  tags: [FDb].} =
+  tags: [DbEffect].} =
   ## sets the encoding of a database connection, returns true for
   ## success, false for failure.
   ##
diff --git a/lib/pure/db_common.nim b/lib/pure/db_common.nim
new file mode 100644
index 000000000..522d13db2
--- /dev/null
+++ b/lib/pure/db_common.nim
@@ -0,0 +1,96 @@
+#
+#
+#            Nim's Runtime Library
+#        (c) Copyright 2015 Andreas Rumpf
+#
+#    See the file "copying.txt", included in this
+#    distribution, for details about the copyright.
+#
+
+## Common datatypes and definitions for all db_*.nim modules.
+
+type
+  DbError* = object of IOError ## exception that is raised if a database error occurs
+
+  SqlQuery* = distinct string ## an SQL query string
+
+
+  DbEffect* = object of IOEffect ## effect that denotes a database operation
+  ReadDbEffect* = object of DbEffect   ## effect that denotes a read operation
+  WriteDbEffect* = object of DbEffect  ## effect that denotes a write operation
+
+  DbTypeKind* = enum  ## a superset of datatypes that might be supported.
+    dbUnknown,        ## unknown datatype
+    dbSerial,         ## datatype used for primary auto-increment keys
+    dbNull,           ## datatype used for the NULL value
+    dbBit,            ## bit datatype
+    dbBool,           ## boolean datatype
+    dbBlob,           ## blob datatype
+    dbFixedChar,      ## string of fixed length
+    dbVarchar,        ## string datatype
+    dbJson,           ## JSON datatype
+    dbXml,            ## XML datatype
+    dbInt,            ## some integer type
+    dbUInt,           ## some unsigned integer type
+    dbDecimal,        ## decimal numbers (fixed-point number)
+    dbFloat,          ## some floating point type
+    dbDate,           ## a year-month-day description
+    dbTime,           ## HH:MM:SS information
+    dbDatetime,       ## year-month-day and HH:MM:SS information
+    dbTimestamp,      ## Timestamp values are stored as the number of seconds
+                      ## since the epoch ('1970-01-01 00:00:00' UTC).
+    dbTimeInterval,   ## an interval [a,b] of times
+    dbEnum,           ## some enum
+    dbSet,            ## set of enum values
+    dbArray,          ## an array of values
+    dbComposite,      ## composite type (record, struct, etc)
+    dbUrl,            ## a URL
+    dbUuid,           ## a UUID
+    dbInet,           ## an IP address
+    dbMacAddress,     ## a MAC address
+    dbPoint,          ## Point on a plane   (x,y)
+    dbLine,           ## Infinite line ((x1,y1),(x2,y2))
+    dbLseg,           ## Finite line segment   ((x1,y1),(x2,y2))
+    dbBox,            ## Rectangular box   ((x1,y1),(x2,y2))
+    dbPath,           ## Closed or open path (similar to polygon) ((x1,y1),...)
+    dbPolygon,        ## Polygon (similar to closed path)   ((x1,y1),...)
+    dbCircle,         ## Circle   <(x,y),r> (center point and radius)
+    dbUser1,          ## user definable datatype 1 (for unknown extensions)
+    dbUser2,          ## user definable datatype 2 (for unknown extensions)
+    dbUser3,          ## user definable datatype 3 (for unknown extensions)
+    dbUser4,          ## user definable datatype 4 (for unknown extensions)
+    dbUser5           ## user definable datatype 5 (for unknown extensions)
+
+  DbType* = object    ## describes a database type
+    kind*: DbTypeKind ## the kind of the described type
+    notNull*: bool    ## does the type contain NULL?
+    name*: string     ## the name of the type
+    size*: Natural    ## the size of the datatype; 0 if of variable size
+    precision*, scale*: Natural ## precision and scale of the number
+    min*, max*: BiggestInt ## the minimum and maximum of allowed values
+    validValues*: seq[string] ## valid values of an enum or a set
+
+  DbColumn* = object   ## information about a database column
+    name*: string      ## name of the column
+    tableName*: string ## name of the table the column belongs to (optional)
+    typ*: DbType       ## type of the column
+  DbColumns* = seq[DbColumn]
+
+{.deprecated: [EDb: DbError, TSqlQuery: SqlQuery, FDb: DbEffect,
+              FReadDb: ReadDbEffect, FWriteDb: WriteDbEffect].}
+
+template sql*(query: string): SqlQuery =
+  ## constructs a SqlQuery from the string `query`. This is supposed to be
+  ## used as a raw-string-literal modifier:
+  ## ``sql"update user set counter = counter + 1"``
+  ##
+  ## If assertions are turned off, it does nothing. If assertions are turned
+  ## on, later versions will check the string for valid syntax.
+  SqlQuery(query)
+
+proc dbError*(msg: string) {.noreturn, noinline.} =
+  ## raises an DbError exception with message `msg`.
+  var e: ref DbError
+  new(e)
+  e.msg = msg
+  raise e