db_postgres

A higher level PostgreSQL database wrapper. This interface is implemented for other databases also.

See also: db_odbc, db_sqlite, db_mysql.

Parameter substitution

All db_* modules support the same form of parameter substitution. That is, using the ? (question mark) to signify the place where a value should be placed. For example:

sql"INSERT INTO myTable (colA, colB, colC) VALUES (?, ?, ?)"

Note: There are two approaches to parameter substitution support by this module.

1. SqlQuery using ?, ?, ?, ... (same as all the db_* modules)

2. SqlPrepared using $1, $2, $3, ...

prepare(db, "myExampleInsert",
        sql"""INSERT INTO myTable
              (colA, colB, colC)
              VALUES ($1, $2, $3)""",
        3)

Examples

Opening a connection to a database

import db_postgres
let db = open("localhost", "user", "password", "dbname")
db.close()

Creating a table

db.exec(sql"DROP TABLE IF EXISTS myTable")
db.exec(sql("""CREATE TABLE myTable (
                 id integer,
                 name varchar(50) not null)"""))

Inserting data

db.exec(sql"INSERT INTO myTable (id, name) VALUES (0, ?)",
        "Dominik")

Types

DbConn = PPGconn
encapsulates a database connection   Source Edit
Row = seq[string]
a row of a dataset. NULL database values will be converted to nil.   Source Edit
InstantRow = object
  res: PPGresult               ## used to get a row's
  line: int                    ## column text on demand
  
a handle that can be   Source Edit
SqlPrepared = distinct string
a identifier for the prepared queries   Source Edit

Procs

proc dbError(db: DbConn) {...}{.noreturn, raises: [DbError], tags: [].}
raises a DbError exception.   Source Edit
proc dbQuote(s: string): string {...}{.raises: [], tags: [].}
DB quotes the string.   Source Edit
proc tryExec(db: DbConn; query: SqlQuery; args: varargs[string, `$`]): bool {...}{.
    tags: [ReadDbEffect, WriteDbEffect], raises: [DbError].}
tries to execute the query and returns true if successful, false otherwise.   Source Edit
proc tryExec(db: DbConn; stmtName: SqlPrepared; args: varargs[string, `$`]): bool {...}{.
    tags: [ReadDbEffect, WriteDbEffect], raises: [].}
tries to execute the query and returns true if successful, false otherwise.   Source Edit
proc exec(db: DbConn; query: SqlQuery; args: varargs[string, `$`]) {...}{.
    tags: [ReadDbEffect, WriteDbEffect], raises: [DbError].}
executes the query and raises EDB if not successful.   Source Edit
proc exec(db: DbConn; stmtName: SqlPrepared; args: varargs[string]) {...}{.
    tags: [ReadDbEffect, WriteDbEffect], raises: [DbError].}
  Source Edit
proc prepare(db: DbConn; stmtName: string; query: SqlQuery; nParams: int): SqlPrepared {...}{.
    raises: [DbError], tags: [].}
Creates a new SqlPrepared statement. Parameter substitution is done via $1, $2, $3, etc.   Source Edit
proc `[]`(row: InstantRow; col: int): string {...}{.inline, raises: [], tags: [].}
returns text for given column of the row   Source Edit
proc unsafeColumnAt(row: InstantRow; index: int): cstring {...}{.inline, raises: [], tags: [].}
Return cstring of given column of the row   Source Edit
proc len(row: InstantRow): int {...}{.inline, raises: [], tags: [].}
returns number of columns in the row   Source Edit
proc getRow(db: DbConn; query: SqlQuery; args: varargs[string, `$`]): Row {...}{.
    tags: [ReadDbEffect], raises: [DbError].}
retrieves a single row. If the query doesn't return any rows, this proc will return a Row with empty strings for each column.   Source Edit
proc getRow(db: DbConn; stmtName: SqlPrepared; args: varargs[string, `$`]): Row {...}{.
    tags: [ReadDbEffect], raises: [DbError].}
  Source Edit
proc getAllRows(db: DbConn; query: SqlQuery; args: varargs[string, `$`]): seq[Row] {...}{.
    tags: [ReadDbEffect], raises: [DbError].}
executes the query and returns the whole result dataset.   Source Edit
proc getAllRows(db: DbConn; stmtName: SqlPrepared; args: varargs[string, `$`]): seq[Row] {...}{.
    tags: [ReadDbEffect], raises: [DbError].}
executes the prepared query and returns the whole result dataset.   Source Edit
proc getValue(db: DbConn; query: SqlQuery; args: varargs[string, `$`]): string {...}{.
    tags: [ReadDbEffect], raises: [DbError].}
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.   Source Edit
proc getValue(db: DbConn; stmtName: SqlPrepared; args: varargs[string, `$`]): string {...}{.
    tags: [ReadDbEffect], raises: [DbError].}
executes the query and returns the first column of the first row of the result dataset. Returns "" if the dataset contains no rows or the database value is NULL.   Source Edit
proc tryInsertID(db: DbConn; query: SqlQuery; args: varargs[string, `$`]): int64 {...}{.
    tags: [WriteDbEffect], raises: [DbError, ValueError].}
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.   Source Edit
proc insertID(db: DbConn; query: SqlQuery; args: varargs[string, `$`]): int64 {...}{.
    tags: [WriteDbEffect], raises: [DbError, ValueError].}
executes the query (typically "INSERT") and returns the generated ID for the row. For Postgre this adds RETURNING id to the query, so it only works if your primary key is named id.   Source Edit
proc tryInsert(db: DbConn; query: SqlQuery; pkName: string; args: varargs[string, `$`]): int64 {...}{.
    tags: [WriteDbEffect], raises: [DbError, ValueError].}
executes the query (typically "INSERT") and returns the generated ID for the row or -1 in case of an error.   Source Edit
proc insert(db: DbConn; query: SqlQuery; pkName: string; args: varargs[string, `$`]): int64 {...}{.
    tags: [WriteDbEffect], raises: [DbError, ValueError].}
executes the query (typically "INSERT") and returns the generated ID   Source Edit
proc execAffectedRows(db: DbConn; query: SqlQuery; args: varargs[string, `$`]): int64 {...}{.
    tags: [ReadDbEffect, WriteDbEffect], raises: [DbError, ValueError].}
executes the query (typically "UPDATE") and returns the number of affected rows.   Source Edit
proc execAffectedRows(db: DbConn; stmtName: SqlPrepared; args: varargs[string, `$`]): int64 {...}{.
    tags: [ReadDbEffect, WriteDbEffect], raises: [DbError, ValueError].}
executes the query (typically "UPDATE") and returns the number of affected rows.   Source Edit
proc close(db: DbConn) {...}{.tags: [DbEffect], raises: [].}
closes the database connection.   Source Edit
proc open(connection, user, password, database: string): DbConn {...}{.tags: [DbEffect],
    raises: [DbError].}

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:

con = open("", "", "", "host=localhost port=5432 dbname=mydb")

See http://www.postgresql.org/docs/current/static/libpq-connect.html#LIBPQ-CONNSTRING for more information.

  Source Edit
proc setEncoding(connection: DbConn; encoding: string): bool {...}{.tags: [DbEffect],
    raises: [].}
sets the encoding of a database connection, returns true for success, false for failure.   Source Edit

Iterators

iterator fastRows(db: DbConn; query: SqlQuery; args: varargs[string, `$`]): Row {...}{.
    tags: [ReadDbEffect], raises: [DbError].}
executes the query and iterates over the result dataset. This is very fast, but potentially dangerous: If the for-loop-body executes another query, the results can be undefined. For Postgres it is safe though.   Source Edit
iterator fastRows(db: DbConn; stmtName: SqlPrepared; args: varargs[string, `$`]): Row {...}{.
    tags: [ReadDbEffect], raises: [DbError].}
executes the prepared query and iterates over the result dataset.   Source Edit
iterator instantRows(db: DbConn; query: SqlQuery; args: varargs[string, `$`]): InstantRow {...}{.
    tags: [ReadDbEffect], raises: [DbError].}
same as fastRows but returns a handle that can be used to get column text on demand using []. Returned handle is valid only within iterator body.   Source Edit
iterator instantRows(db: DbConn; stmtName: SqlPrepared; args: varargs[string, `$`]): InstantRow {...}{.
    tags: [ReadDbEffect], raises: [DbError].}
same as fastRows but returns a handle that can be used to get column text on demand using []. Returned handle is valid only within iterator body.   Source Edit
iterator instantRows(db: DbConn; columns: var DbColumns; query: SqlQuery;
                    args: varargs[string, `$`]): InstantRow {...}{.tags: [ReadDbEffect],
    raises: [DbError].}
  Source Edit
iterator rows(db: DbConn; query: SqlQuery; args: varargs[string, `$`]): Row {...}{.
    tags: [ReadDbEffect], raises: [DbError].}
same as fastRows, but slower and safe.   Source Edit
iterator rows(db: DbConn; stmtName: SqlPrepared; args: varargs[string, `$`]): Row {...}{.
    tags: [ReadDbEffect], raises: [DbError].}
same as fastRows, but slower and safe.   Source Edit