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Add postgresql prepared queries and stop relying on string formatting
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for sql parameter passing
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@idlewan
idlewan committed Aug 29, 2014
1 parent 2525215 commit 08f1c61
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Showing 2 changed files with 86 additions and 28 deletions.
112 changes: 84 additions & 28 deletions lib/impure/db_postgres.nim
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Original file line number Diff line number Diff line change
Expand Up @@ -19,12 +19,13 @@ type
EDb* = object of EIO ## 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 FIO ## 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.} =

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"``
Expand All @@ -33,14 +34,14 @@ proc sql*(query: string): TSqlQuery {.noSideEffect, inline.} =
## on, later versions will check the string for valid syntax.
result = TSqlQuery(query)

proc dbError(db: TDbConn) {.noreturn.} =
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.} =
proc dbError*(msg: string) {.noreturn.} =
## raises an EDb exception with message `msg`.
var e: ref EDb
new(e)
Expand All @@ -61,41 +62,70 @@ proc dbFormat(formatstr: TSqlQuery, args: varargs[string]): string =
if c == '?':
add(result, dbQuote(args[a]))
inc(a)
else:
else:
add(result, c)

proc tryExec*(db: TDbConn, query: TSqlQuery,
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)
var res = PQExec(db, q)
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 q = dbFormat(query, args)
var res = PQExec(db, q)
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 q = dbFormat(query, args)
result = PQExec(db, q)
if PQresultStatus(result) != PGRES_TUPLES_OK: dbError(db)

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
Expand All @@ -109,6 +139,17 @@ iterator fastRows*(db: TDbConn, query: TSqlQuery,
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
Expand All @@ -119,40 +160,55 @@ proc getRow*(db: TDbConn, query: TSqlQuery,
setRow(res, result, 0, L)
PQclear(res)

proc getAllRows*(db: TDbConn, query: TSqlQuery,
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)

iterator rows*(db: TDbConn, query: TSqlQuery,
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, `$`]): string {.tags: [FReadDB].} =
proc getValue*(db: TDbConn, query: TSqlQuery,
args: varargs[string, `$`]): 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,
proc tryInsertID*(db: TDbConn, query: TSqlQuery,
args: varargs[string, `$`]): int64 {.tags: [FWriteDb].}=
## executes the query (typically "INSERT") and returns the
## generated ID for the row or -1 in case of an error. For Postgre this adds
## ``RETURNING id`` to the query, so it only works if your primary key is
## named ``id``.
var x = PQgetvalue(setupQuery(db, TSqlQuery(string(query) & " RETURNING id"),
var x = PQgetvalue(setupQuery(db, TSqlQuery(string(query) & " RETURNING id"),
args), 0, 0)
if not isNil(x):
result = ParseBiggestInt($x)
else:
result = -1

proc insertID*(db: TDbConn, query: TSqlQuery,
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
Expand All @@ -161,9 +217,9 @@ proc insertID*(db: TDbConn, query: TSqlQuery,
result = TryInsertID(db, query, args)
if result < 0: dbError(db)

proc execAffectedRows*(db: TDbConn, query: TSqlQuery,
proc execAffectedRows*(db: TDbConn, query: TSqlQuery,
args: varargs[string, `$`]): int64 {.tags: [
FReadDB, FWriteDb].} =
FReadDB, FWriteDb].} =
## executes the query (typically "UPDATE") and returns the
## number of affected rows.
var q = dbFormat(query, args)
Expand All @@ -172,7 +228,7 @@ proc execAffectedRows*(db: TDbConn, query: TSqlQuery,
result = parseBiggestInt($PQcmdTuples(res))
PQclear(res)

proc close*(db: TDbConn) {.tags: [FDb].} =
proc close*(db: TDbConn) {.tags: [FDb].} =
## closes the database connection.
if db != nil: PQfinish(db)

Expand Down
2 changes: 2 additions & 0 deletions lib/wrappers/postgres.nim
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Original file line number Diff line number Diff line change
Expand Up @@ -213,6 +213,8 @@ proc PQexecParams*(conn: PPGconn, command: cstring, nParams: int32,
paramTypes: POid, paramValues: cstringArray,
paramLengths, paramFormats: ptr int32, resultFormat: int32): PPGresult{.
cdecl, dynlib: dllName, importc: "PQexecParams".}
proc PQprepare*(conn: PPGconn, stmtName, query: cstring, nParams: int32,
paramTypes: POid): PPGresult{.cdecl, dynlib: dllName, importc: "PQprepare".}
proc PQexecPrepared*(conn: PPGconn, stmtName: cstring, nParams: int32,
paramValues: cstringArray,
paramLengths, paramFormats: ptr int32, resultFormat: int32): PPGresult{.
Expand Down

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