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#
#
# Nim's Runtime Library
# (c) Copyright 2014 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. NULL database values will be
## transformed always to the empty string.
EDb* = object of IOError ## exception that is raised if a database error occurs
TSqlQuery* = distinct string ## an SQL query string
TSqlPrepared* = 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
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 = $pqErrorMessage(db)
raise e
proc dbError*(msg: string) {.noreturn.} =
## raises an EDb exception with message `msg`.
var e: ref EDb
new(e)
e.msg = msg
raise e
proc dbQuote(s: string): string =
result = "'"
for c in items(s):
if c == '\'': add(result, "''")
else: add(result, c)
add(result, '\'')
proc dbFormat(formatstr: TSqlQuery, args: varargs[string]): string =
result = ""
var a = 0
for c in items(string(formatstr)):
if c == '?':
add(result, dbQuote(args[a]))
inc(a)
else:
add(result, c)
proc tryExec*(db: TDbConn, query: TSqlQuery,
args: varargs[string, `$`]): bool {.tags: [FReadDB, FWriteDb].} =
## tries to execute the query and returns true if successful, false otherwise.
var arr = allocCStringArray(args)
var res = pqexecParams(db, query.string, int32(args.len), nil, arr,
nil, nil, 0)
deallocCStringArray(arr)
result = pqresultStatus(res) == PGRES_COMMAND_OK
pqclear(res)
proc exec*(db: TDbConn, query: TSqlQuery, args: varargs[string, `$`]) {.
tags: [FReadDB, FWriteDb].} =
## executes the query and raises EDB if not successful.
var arr = allocCStringArray(args)
var res = pqexecParams(db, query.string, int32(args.len), nil, arr,
nil, nil, 0)
deallocCStringArray(arr)
if pqresultStatus(res) != PGRES_COMMAND_OK: dbError(db)
pqclear(res)
proc exec*(db: TDbConn, stmtName: TSqlPrepared,
args: varargs[string]) {.tags: [FReadDB, FWriteDb].} =
var arr = allocCStringArray(args)
var res = pqexecPrepared(db, stmtName.string, int32(args.len), arr,
nil, nil, 0)
deallocCStringArray(arr)
if pqResultStatus(res) != PGRES_COMMAND_OK: dbError(db)
pqclear(res)
proc newRow(L: int): TRow =
newSeq(result, L)
for i in 0..L-1: result[i] = ""
proc setupQuery(db: TDbConn, query: TSqlQuery,
args: varargs[string]): PPGresult =
var arr = allocCStringArray(args)
result = pqexecParams(db, query.string, int32(args.len), nil, arr,
nil, nil, 0)
deallocCStringArray(arr)
if pqResultStatus(result) != PGRES_TUPLES_OK: dbError(db)
proc setupQuery(db: TDbConn, stmtName: TSqlPrepared,
args: varargs[string]): PPGresult =
var arr = allocCStringArray(args)
result = pqexecPrepared(db, stmtName.string, int32(args.len), arr,
nil, nil, 0)
deallocCStringArray(arr)
if pqResultStatus(result) != PGRES_TUPLES_OK: dbError(db)
proc prepare*(db: TDbConn; stmtName: string, query: TSqlQuery;
nParams: int): TSqlPrepared =
var res = pqprepare(db, stmtName, query.string, int32(nParams), nil)
if pqResultStatus(res) != PGRES_COMMAND_OK: dbError(db)
return TSqlPrepared(stmtName)
proc setRow(res: PPGresult, r: var TRow, line, cols: int32) =
for col in 0..cols-1:
setLen(r[col], 0)
var x = pqgetvalue(res, line, col)
add(r[col], x)
iterator fastRows*(db: TDbConn, query: TSqlQuery,
args: varargs[string, `$`]): 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 Postgres it is safe though.
var res = setupQuery(db, query, args)
var L = pqnfields(res)
var result = newRow(L)
for i in 0..pqntuples(res)-1:
setRow(res, result, i, L)
yield result
pqclear(res)
iterator fastRows*(db: TDbConn, stmtName: TSqlPrepared,
args: varargs[string, `$`]): TRow {.tags: [FReadDB].} =
## executes the prepared query and iterates over the result dataset.
var res = setupQuery(db, stmtName, args)
var L = PQnfields(res)
var result = newRow(L)
for i in 0..PQntuples(res)-1:
setRow(res, result, i, L)
yield result
PQclear(res)
proc getRow*(db: TDbConn, query: TSqlQuery,
args: varargs[string, `$`]): TRow {.tags: [FReadDB].} =
## retrieves a single row. If the query doesn't return any rows, this proc
## will return a TRow with empty strings for each column.
var res = setupQuery(db, query, args)
var L = pqnfields(res)
result = newRow(L)
setRow(res, result, 0, L)
pqclear(res)
proc getRow*(db: TDbConn, stmtName: TSqlPrepared,
args: varargs[string, `$`]): TRow {.tags: [FReadDB].} =
var res = setupQuery(db, stmtName, args)
var L = PQnfields(res)
result = newRow(L)
setRow(res, result, 0, L)
PQclear(res)
proc getAllRows*(db: TDbConn, query: TSqlQuery,
args: varargs[string, `$`]): seq[TRow] {.tags: [FReadDB].} =
## executes the query and returns the whole result dataset.
result = @[]
for r in fastRows(db, query, args):
result.add(r)
proc getAllRows*(db: TDbConn, stmtName: TSqlPrepared,
args: varargs[string, `$`]): seq[TRow] {.tags: [FReadDB].} =
## executes the prepared query and returns the whole result dataset.
result = @[]
for r in FastRows(db, stmtName, args):
result.add(r)
iterator rows*(db: TDbConn, query: TSqlQuery,
args: varargs[string, `$`]): 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 {.tags: [FReadDB].} =
## 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.
var x = pqgetvalue(setupQuery(db, query, args), 0, 0)
result = if isNil(x): "" else: $x
proc tryInsertID*(db: TDbConn, query: TSqlQuery,
args: varargs[string, `$`]): int64 {.tags: [FWriteDb].}=
## executes the query (typically "INSERT") and returns the
## generated ID for the row or -1 in case of an error. For Postgre this adds
## ``RETURNING id`` to the query, so it only works if your primary key is
## named ``id``.
var x = pqgetvalue(setupQuery(db, TSqlQuery(string(query) & " RETURNING id"),
args), 0, 0)
if not isNil(x):
result = parseBiggestInt($x)
else:
result = -1
proc insertID*(db: TDbConn, query: TSqlQuery,
args: varargs[string, `$`]): int64 {.tags: [FWriteDb].} =
## 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: varargs[string, `$`]): int64 {.tags: [
FReadDB, FWriteDb].} =
## executes the query (typically "UPDATE") and returns the
## number of affected rows.
var q = dbFormat(query, args)
var res = pqExec(db, q)
if pqresultStatus(res) != PGRES_COMMAND_OK: dbError(db)
result = parseBiggestInt($pqcmdTuples(res))
pqclear(res)
proc close*(db: TDbConn) {.tags: [FDb].} =
## closes the database connection.
if db != nil: pqfinish(db)
proc open*(connection, user, password, database: string): TDbConn {.
tags: [FDb].} =
## opens a database connection. Raises `EDb` if the connection could not
## be established.
##
## Clients can also use Postgres keyword/value connection strings to
## connect.
##
## Example:
##
## .. code-block:: nim
##
## con = open("", "", "", "host=localhost port=5432 dbname=mydb")
##
## See http://www.postgresql.org/docs/current/static/libpq-connect.html#LIBPQ-CONNSTRING
## for more information.
##
## Note that the connection parameter is not used but exists to maintain
## the nim db api.
result = pqsetdbLogin(nil, nil, nil, nil, database, user, password)
if pqStatus(result) != CONNECTION_OK: dbError(result) # result = nil
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