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292 lines
10 KiB
Nim
292 lines
10 KiB
Nim
#
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#
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# Nim's Runtime Library
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# (c) Copyright 2015 Andreas Rumpf
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#
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# See the file "copying.txt", included in this
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# distribution, for details about the copyright.
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#
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## A higher level `PostgreSQL`:idx: database wrapper. This interface
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## is implemented for other databases too.
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import strutils, postgres
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type
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DbConn* = PPGconn ## encapsulates a database connection
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Row* = seq[string] ## a row of a dataset. NULL database values will be
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## transformed always to the empty string.
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InstantRow* = tuple[res: PPGresult, line: int32] ## a handle that can be
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## used to get a row's
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## column text on demand
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EDb* = object of IOError ## exception that is raised if a database error occurs
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SqlQuery* = distinct string ## an SQL query string
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SqlPrepared* = distinct string ## a identifier for the prepared queries
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FDb* = object of IOEffect ## effect that denotes a database operation
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FReadDb* = object of FDb ## effect that denotes a read operation
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FWriteDb* = object of FDb ## effect that denotes a write operation
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{.deprecated: [TRow: Row, TSqlQuery: SqlQuery, TDbConn: DbConn,
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TSqlPrepared: SqlPrepared].}
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proc sql*(query: string): SqlQuery {.noSideEffect, inline.} =
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## constructs a SqlQuery from the string `query`. This is supposed to be
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## used as a raw-string-literal modifier:
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## ``sql"update user set counter = counter + 1"``
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##
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## If assertions are turned off, it does nothing. If assertions are turned
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## on, later versions will check the string for valid syntax.
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result = SqlQuery(query)
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proc dbError*(db: DbConn) {.noreturn.} =
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## raises an EDb exception.
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var e: ref EDb
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new(e)
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e.msg = $pqErrorMessage(db)
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raise e
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proc dbError*(msg: string) {.noreturn.} =
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## raises an EDb exception with message `msg`.
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var e: ref EDb
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new(e)
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e.msg = msg
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raise e
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proc dbQuote*(s: string): string =
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## DB quotes the string.
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result = "'"
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for c in items(s):
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if c == '\'': add(result, "''")
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else: add(result, c)
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add(result, '\'')
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proc dbFormat(formatstr: SqlQuery, args: varargs[string]): string =
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result = ""
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var a = 0
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for c in items(string(formatstr)):
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if c == '?':
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if args[a] == nil:
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add(result, "NULL")
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else:
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add(result, dbQuote(args[a]))
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inc(a)
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else:
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add(result, c)
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proc tryExec*(db: DbConn, query: SqlQuery,
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args: varargs[string, `$`]): bool {.tags: [FReadDB, FWriteDb].} =
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## tries to execute the query and returns true if successful, false otherwise.
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var arr = allocCStringArray(args)
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var res = pqexecParams(db, query.string, int32(args.len), nil, arr,
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nil, nil, 0)
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deallocCStringArray(arr)
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result = pqresultStatus(res) == PGRES_COMMAND_OK
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pqclear(res)
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proc exec*(db: DbConn, query: SqlQuery, args: varargs[string, `$`]) {.
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tags: [FReadDB, FWriteDb].} =
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## executes the query and raises EDB if not successful.
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var arr = allocCStringArray(args)
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var res = pqexecParams(db, query.string, int32(args.len), nil, arr,
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nil, nil, 0)
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deallocCStringArray(arr)
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if pqresultStatus(res) != PGRES_COMMAND_OK: dbError(db)
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pqclear(res)
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proc exec*(db: DbConn, stmtName: SqlPrepared,
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args: varargs[string]) {.tags: [FReadDB, FWriteDb].} =
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var arr = allocCStringArray(args)
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var res = pqexecPrepared(db, stmtName.string, int32(args.len), arr,
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nil, nil, 0)
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deallocCStringArray(arr)
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if pqResultStatus(res) != PGRES_COMMAND_OK: dbError(db)
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pqclear(res)
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proc newRow(L: int): Row =
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newSeq(result, L)
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for i in 0..L-1: result[i] = ""
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proc setupQuery(db: DbConn, query: SqlQuery,
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args: varargs[string]): PPGresult =
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var arr = allocCStringArray(args)
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result = pqexecParams(db, query.string, int32(args.len), nil, arr,
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nil, nil, 0)
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deallocCStringArray(arr)
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if pqResultStatus(result) != PGRES_TUPLES_OK: dbError(db)
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proc setupQuery(db: DbConn, stmtName: SqlPrepared,
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args: varargs[string]): PPGresult =
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var arr = allocCStringArray(args)
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result = pqexecPrepared(db, stmtName.string, int32(args.len), arr,
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nil, nil, 0)
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deallocCStringArray(arr)
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if pqResultStatus(result) != PGRES_TUPLES_OK: dbError(db)
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proc prepare*(db: DbConn; stmtName: string, query: SqlQuery;
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nParams: int): SqlPrepared =
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var res = pqprepare(db, stmtName, query.string, int32(nParams), nil)
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if pqResultStatus(res) != PGRES_COMMAND_OK: dbError(db)
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return SqlPrepared(stmtName)
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proc setRow(res: PPGresult, r: var Row, line, cols: int32) =
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for col in 0..cols-1:
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setLen(r[col], 0)
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let x = pqgetvalue(res, line, col)
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if x.isNil:
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r[col] = nil
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else:
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add(r[col], x)
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iterator fastRows*(db: DbConn, query: SqlQuery,
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args: varargs[string, `$`]): Row {.tags: [FReadDB].} =
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## executes the query and iterates over the result dataset. This is very
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## fast, but potenially dangerous: If the for-loop-body executes another
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## query, the results can be undefined. For Postgres it is safe though.
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var res = setupQuery(db, query, args)
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var L = pqnfields(res)
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var result = newRow(L)
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for i in 0..pqntuples(res)-1:
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setRow(res, result, i, L)
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yield result
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pqclear(res)
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iterator fastRows*(db: DbConn, stmtName: SqlPrepared,
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args: varargs[string, `$`]): Row {.tags: [FReadDB].} =
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## executes the prepared query and iterates over the result dataset.
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var res = setupQuery(db, stmtName, args)
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var L = pqNfields(res)
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var result = newRow(L)
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for i in 0..pqNtuples(res)-1:
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setRow(res, result, i, L)
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yield result
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pqClear(res)
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iterator instantRows*(db: DbConn, query: SqlQuery,
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args: varargs[string, `$`]): InstantRow
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{.tags: [FReadDb].} =
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## same as fastRows but returns a handle that can be used to get column text
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## on demand using []. Returned handle is valid only within interator body.
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var res = setupQuery(db, query, args)
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for i in 0..pqNtuples(res)-1:
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yield (res: res, line: i)
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pqClear(res)
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proc `[]`*(row: InstantRow, col: int32): string {.inline.} =
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## returns text for given column of the row
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$pqgetvalue(row.res, row.line, col)
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proc len*(row: InstantRow): int32 {.inline.} =
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## returns number of columns in the row
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pqNfields(row.res)
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proc getRow*(db: DbConn, query: SqlQuery,
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args: varargs[string, `$`]): Row {.tags: [FReadDB].} =
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## retrieves a single row. If the query doesn't return any rows, this proc
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## will return a Row with empty strings for each column.
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var res = setupQuery(db, query, args)
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var L = pqnfields(res)
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result = newRow(L)
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setRow(res, result, 0, L)
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pqclear(res)
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proc getRow*(db: DbConn, stmtName: SqlPrepared,
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args: varargs[string, `$`]): Row {.tags: [FReadDB].} =
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var res = setupQuery(db, stmtName, args)
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var L = pqNfields(res)
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result = newRow(L)
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setRow(res, result, 0, L)
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pqClear(res)
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proc getAllRows*(db: DbConn, query: SqlQuery,
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args: varargs[string, `$`]): seq[Row] {.tags: [FReadDB].} =
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## executes the query and returns the whole result dataset.
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result = @[]
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for r in fastRows(db, query, args):
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result.add(r)
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proc getAllRows*(db: DbConn, stmtName: SqlPrepared,
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args: varargs[string, `$`]): seq[Row] {.tags: [FReadDB].} =
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## executes the prepared query and returns the whole result dataset.
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result = @[]
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for r in fastRows(db, stmtName, args):
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result.add(r)
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iterator rows*(db: DbConn, query: SqlQuery,
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args: varargs[string, `$`]): Row {.tags: [FReadDB].} =
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## same as `fastRows`, but slower and safe.
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for r in items(getAllRows(db, query, args)): yield r
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proc getValue*(db: DbConn, query: SqlQuery,
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args: varargs[string, `$`]): string {.tags: [FReadDB].} =
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## executes the query and returns the first column of the first row of the
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## result dataset. Returns "" if the dataset contains no rows or the database
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## value is NULL.
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var x = pqgetvalue(setupQuery(db, query, args), 0, 0)
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result = if isNil(x): "" else: $x
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proc tryInsertID*(db: DbConn, query: SqlQuery,
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args: varargs[string, `$`]): int64 {.tags: [FWriteDb].}=
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## executes the query (typically "INSERT") and returns the
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## generated ID for the row or -1 in case of an error. For Postgre this adds
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## ``RETURNING id`` to the query, so it only works if your primary key is
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## named ``id``.
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var x = pqgetvalue(setupQuery(db, SqlQuery(string(query) & " RETURNING id"),
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args), 0, 0)
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if not isNil(x):
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result = parseBiggestInt($x)
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else:
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result = -1
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proc insertID*(db: DbConn, query: SqlQuery,
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args: varargs[string, `$`]): int64 {.tags: [FWriteDb].} =
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## executes the query (typically "INSERT") and returns the
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## generated ID for the row. For Postgre this adds
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## ``RETURNING id`` to the query, so it only works if your primary key is
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## named ``id``.
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result = tryInsertID(db, query, args)
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if result < 0: dbError(db)
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proc execAffectedRows*(db: DbConn, query: SqlQuery,
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args: varargs[string, `$`]): int64 {.tags: [
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FReadDB, FWriteDb].} =
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## executes the query (typically "UPDATE") and returns the
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## number of affected rows.
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var q = dbFormat(query, args)
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var res = pqExec(db, q)
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if pqresultStatus(res) != PGRES_COMMAND_OK: dbError(db)
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result = parseBiggestInt($pqcmdTuples(res))
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pqclear(res)
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proc close*(db: DbConn) {.tags: [FDb].} =
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## closes the database connection.
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if db != nil: pqfinish(db)
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proc open*(connection, user, password, database: string): DbConn {.
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tags: [FDb].} =
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## opens a database connection. Raises `EDb` if the connection could not
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## be established.
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##
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## Clients can also use Postgres keyword/value connection strings to
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## connect.
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##
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## Example:
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##
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## .. code-block:: nim
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##
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## con = open("", "", "", "host=localhost port=5432 dbname=mydb")
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##
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## See http://www.postgresql.org/docs/current/static/libpq-connect.html#LIBPQ-CONNSTRING
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## for more information.
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##
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## Note that the connection parameter is not used but exists to maintain
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## the nim db api.
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result = pqsetdbLogin(nil, nil, nil, nil, database, user, password)
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if pqStatus(result) != CONNECTION_OK: dbError(result) # result = nil
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proc setEncoding*(connection: DbConn, encoding: string): bool {.
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tags: [FDb].} =
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## sets the encoding of a database connection, returns true for
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## success, false for failure.
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return pqsetClientEncoding(connection, encoding) == 0
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