reshuffle-pgsql-connector
v0.0.2
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Reshuffle connectors to PostgreSQL
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reshuffle-pgsql-connector
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npm install reshuffle-pgsql-connector
Reshuffle Postgres SQL Connector
This package contains a Reshuffle connector to Postgres SQL databases.
The following example lists all information from the "users" table:
const { Reshuffle } = require('reshuffle')
const { PgsqlConnector } = require('reshuffle-pgsql-connector')
;(async () => {
const app = new Reshuffle()
const pg = new PgsqlConnector(app, { url: process.env.POSTGRES_URL })
const res = await pg.query(`SELECT * FROM users`)
console.log(res)
await pg.close()
})().catch(console.error)
Table of Contents
Configuration Configuration options
Connector actions:
close Close all active connections
query Run a single query on the database
sequence Run a series of queries on the databse
transaction Run a transaction on the databae
Configuration options
const app = new Reshuffle();
const pg = new PgsqlConnector(app, {
url: "postgres://user[:password]@hostname[:port]/database",
//Only include ssl option when connecting to a database protected by ssl
ssl: {
rejectUnauthorized: false,
// Configure any of the relevant options below to your own ssl details
ca: fs.readFileSync("/path/to/server-certificates/root.crt").toString(),
key: fs.readFileSync("/path/to/client-key/postgresql.key").toString(),
cert: fs
.readFileSync("/path/to/client-certificates/postgresql.crt")
.toString(),
},
});
If connecting to a local database, ssl
option is not needed and can be left blank.
For more information check the ssl and TLSSocket documentation.
Connector actions
Close action
Definition:
() => void
Usage:
await pg.close()
Close all connections to the database. If an application terminates without calling close, it might hang for a few seconds until active connections time out.
Query action
Definition:
(
sql: string,
params?: any[],
) => {
fields: { name: string }[],
rows: any[],
rowCount: number,
}
Usage:
await pg.query("INSERT INTO users VALUES ('John', 'Coltrane', 42)")
const family = await pg.query(
"SELECT firstName, lastName, age FROM users WHERE lastName='Coltrane'"
)
// {
// rowCount: 2,
// fields: [{ name: 'firstName' }, { name: 'lastName' }, { name: 'age' }],
// rows: [
// { firstName: 'Alice', lastName: 'Coltrane', age: 31 },
// { firstName: 'John', lastName: 'Coltrane', age: 42 },
// ],
// }
const avgResponse = await pg.query(
"SELECT average(age) AS avg FROM users WHERE lastName='Coltrane'"
)
const averageAge = avgResponse.rows[0].avg
// 36.5
The query
action can be used to run any SQL command on the connected
database (not just SELECT
). The query is defined in the sql
string. The
optional params
can be used to generate parameterized queries, as shown in
the following example:
const age = await pg.query(
"SELECT age FROM users WHERE firstName=$1 and lastName=$2",
['John', 'Smith']
)
This action returns an object with the results of the query, where
fields
is an array of all field names, as returned by the query.
Field names in a SELECT
query are column names, or are specified
with an AS
clause. Every element of rows
is uses the names in
fields
as its object keys.
Note that every call to query
may use a different database connection.
You can use the sequence or transaction actions
if such a guarantee is required.
Sequence action
Definition:
(
seq: (query) => any,
) => any
Usage:
const res = await pg.sequence(async (query) => {
await query("INSERT INTO users VALUES ('Miles', 'Davis', 43)")
return query("SELECT COUNT(*) FROM users")
})
const userCount = res.rows[0].count
// 3
Use sequence
to perform multiple queries on the same database connection.
This action receives a seq
function that may issue queries to the database,
all of which are guaranteed to run through the same connection. seq
gets
one argument, which is a query
function that can be used the same way as
the query action. seq
may, of course, use any JavaScript code to
implement its logic, log to the console etc.
Note that while sequence
uses the same connection to run all queries, it
does not offer the transactional guarantees offered by
transaction. You can use it for weak isolation models, or
construct transactions directly without using transaction
.
Transaction action
Definition:
(
seq: (query) => any,
) => any
Usage:
await pg.transaction(async (query) => {
const res = await query("SELECT COUNT(*) FROM users")
const userCount = res.rows[0].count
if (100 <= userCount) {
throw new Error('Too many users:', userCount)
}
return query("INSERT INTO users VALUES ('Charlie', 'Parker', 49)")
})
Use transaction
to run multiple queries as an atomic SQL transaction.
The interface is identical to the sequence action, but all
the queries issued seq
either success or fail together. If any of the
queries fail, all queries are rolled back and an error is thrown.
Consider, for example, the following code for updating a bank account balance:
const accountId = 289
const change = +1000
pg.transaction(async (query) => {
await query(`
UPDATE accounts
SET balance = balance + $1
WHERE account_id = $2
`,
[change, accountId],
)
await query(`
INSERT INTO accounts_log(account_id, change, time)
VALUES ($1, $2, current_timestamp)
`,
[change, accountId],
)
})
In the example above, accounts
holds current balances of accounts,
while accounts_log
holds a history of all changes made. Using transaction
ensures that both tables are always updated together.