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#
#
# Nimrod's Runtime Library
# (c) Copyright 2010 Andreas Rumpf
#
# See the file "copying.txt", included in this
# distribution, for details about the copyright.
#
## A higher level `PostgreSQL`:idx: database wrapper. This interface
## is implemented for other databases too.
import strutils, postgres
type
TDbConn* = PPGconn ## encapsulates a database connection
TRow* = seq[string] ## a row of a dataset
EDb* = object of EIO ## exception that is raised if a database error occurs
TSqlQuery* = distinct string ## an SQL query string
proc sql*(query: string): TSqlQuery {.noSideEffect, inline.} =
## constructs a TSqlQuery 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 = TSqlQuery(query)
proc dbError(db: TDbConn) {.noreturn.} =
## raises an EDb exception.
var e: ref EDb
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 =
result = "'"
for c in items(s):
if c == '\'': add(result, "''")
else: add(result, c)
add(result, '\'')
proc dbFormat(formatstr: TSqlQuery, args: openarray[string]): string =
result = ""
var a = 0
for c in items(string(formatstr)):
if c == '?':
add(result, dbQuote(args[a]))
inc(a)
else:
add(result, c)
proc TryExec*(db: TDbConn, query: TSqlQuery,
args: openarray[string]): bool =
## tries to execute the query and returns true if successful, false otherwise.
var q = dbFormat(query, args)
var res = PQExec(db, q)
result = PQresultStatus(res) == PGRES_COMMAND_OK
PQclear(res)
proc Exec*(db: TDbConn, query: TSqlQuery, args: openarray[string]) =
## executes the query and raises EDB if not successful.
var q = dbFormat(query, args)
var res = PQExec(db, q)
if PQresultStatus(res) != PGRES_COMMAND_OK: dbError(db)
PQclear(res)
proc newRow(L: int): TRow =
newSeq(result, L)
for i in 0..L-1: result[i] = ""
proc setupQuery(db: TDbConn, query: TSqlQuery,
args: openarray[string]): PPGresult =
var q = dbFormat(query, args)
result = PQExec(db, q)
if PQresultStatus(result) != PGRES_TUPLES_OK: dbError(db)
proc setRow(res: PPGresult, r: var TRow, line, cols: int) =
for col in 0..cols-1:
setLen(r[col], 0)
var x = PQgetvalue(res, line, col)
add(r[col], x)
iterator FastRows*(db: TDbConn, query: TSqlQuery,
args: openarray[string]): TRow =
## 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.
var res = setupQuery(db, query, args)
var L = int(PQnfields(res))
var result = newRow(L)
for i in 0..PQntuples(res)-1:
setRow(res, result, i, L)
yield result
PQclear(res)
proc GetAllRows*(db: TDbConn, query: TSqlQuery,
args: openarray[string]): seq[TRow] =
## executes the query and returns the whole result dataset.
result = @[]
for r in FastRows(db, query, args):
result.add(r)
iterator Rows*(db: TDbConn, query: TSqlQuery,
args: openarray[string]): TRow =
## same as `FastRows`, but slower and safe.
for r in items(GetAllRows(db, query, args)): yield r
proc GetValue*(db: TDbConn, query: TSqlQuery,
args: openarray[string]): string =
## executes the query and returns the result dataset's the first column
## of the first row. Returns "" if the dataset contains no rows.
var x = PQgetvalue(setupQuery(db, query, args), 0, 0)
result = if isNil(x): "" else: $x
proc TryInsertID*(db: TDbConn, query: TSqlQuery,
args: openarray[string]): int64 =
## executes the query (typically "INSERT") and returns the
## generated ID for the row or -1 in case of an error. For Postgre this adds
## ``RETURNING id`` to the query, so it only works if your primary key is
## named ``id``.
var val = GetValue(db, TSqlQuery(string(query) & " RETURNING id"), args)
if val.len > 0:
result = ParseBiggestInt(val)
else:
result = -1
proc InsertID*(db: TDbConn, query: TSqlQuery,
args: openArray[string]): int64 =
## executes the query (typically "INSERT") and returns the
## generated ID for the row. For Postgre this adds
## ``RETURNING id`` to the query, so it only works if your primary key is
## named ``id``.
result = TryInsertID(db, query, args)
if result < 0: dbError(db)
proc ExecAffectedRows*(db: TDbConn, query: TSqlQuery,
args: openArray[string]): int64 =
## executes the query (typically "UPDATE") and returns the
## number of affected rows.
var q = dbFormat(query, args)
var res = PQExec(db, q)
if PQresultStatus(res) != PGRES_COMMAND_OK: dbError(db)
result = parseBiggestInt($PQcmdTuples(res))
PQclear(res)
proc Close*(db: TDbConn) =
## closes the database connection.
if db != nil: PQfinish(db)
proc Open*(connection, user, password, database: string): TDbConn =
## opens a database connection. Raises `EDb` if the connection could not
## be established.
result = PQsetdbLogin(nil, nil, nil, nil, database, user, password)
if PQStatus(result) != CONNECTION_OK: dbError(result) # result = nil
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