The pg.Result shape is returned for every successful query.
properties
result.rows: Array<any>
Every result will have a rows array. If no rows are returned the array will be empty. Otherwise the array will contain one item for each row returned from the query. By default node-postgres creates a map from the name to value of each column, giving you a json-like object back for each row.
result.fields: Array<FieldInfo>
Every result will have a fields array. This array contains the name and dataTypeID of each field in the result. These fields are ordered in the same order as the columns if you are using arrayMode for the query:
import pg from 'pg'
const { Pool } = pg
const pool = new Pool()
const client = await pool.connect()
const result = await client.query({
rowMode: 'array',
text: 'SELECT 1 as one, 2 as two;',
})
console.log(result.fields[0].name) // one
console.log(result.fields[1].name) // two
console.log(result.rows) // [ [ 1, 2 ] ]
await client.end()result.command: string
The command type last executed: INSERT UPDATE CREATE SELECT etc.
result.rowCount: int | null
The number of rows processed by the last command. Can be null for commands that never affect rows, such as the LOCK-command. More specifically, some commands, including LOCK, only return a command tag of the form COMMAND, without any [ROWS]-field to parse. For such commands rowCount will be null.
note: this does not reflect the number of rows returned from a query. e.g. an update statement could update many rows (so high result.rowCount value) but result.rows.length would be zero. To check for an empty query response on a SELECT query use result.rows.length === 0.
@sehrope has a good explanation:
The rowCount is populated from the command tag supplied by the PostgreSQL server. It's generally of the form: COMMAND [OID] [ROWS]
For DML commands (INSERT, UPDATE, etc), it reflects how many rows the server modified to process the command. For SELECT or COPY commands it reflects how many rows were retrieved or copied. More info on the specifics here: https://www.postgresql.org/docs/current/protocol-message-formats.html (search for CommandComplete for the message type)
The note in the docs about the difference is because that value is controlled by the server. It's possible for a non-standard server (ex: PostgreSQL fork) or a server version in the future to provide different information in some situations so it'd be best not to rely on it to assume that the rows array length matches the rowCount. It's fine to use it for DML counts though.