postgleam/stream

Stream query results in chunks using portal suspension (Execute with a row limit), so large result sets never sit in memory all at once.

Values

fetch_chunk

</>

pub fn fetch_chunk(
  state: connection.ConnectionState,
  prepared: connection.PreparedStatement,
  registry: dict.Dict(Int, codec.Codec),
  max_rows: Int,
  timeout: Int,
) -> Result(
  #(connection.StreamChunk, connection.ConnectionState),
  error.Error,
)

Fetch a single chunk of rows from an already-bound portal.

fold

</>

pub fn fold(
  state: connection.ConnectionState,
  prepared: connection.PreparedStatement,
  params: List(option.Option(value.Value)),
  registry: dict.Dict(Int, codec.Codec),
  max_rows: Int,
  timeout: Int,
  initial: acc,
  f: fn(acc, List(option.Option(value.Value))) -> acc,
) -> Result(
  #(#(acc, String), connection.ConnectionState),
  error.Error,
)

Fold over a query’s rows, fetching max_rows at a time. Only one chunk is held in memory. Returns the final accumulator and the command tag.

stream_query

</>

pub fn stream_query(
  state: connection.ConnectionState,
  prepared: connection.PreparedStatement,
  params: List(option.Option(value.Value)),
  registry: dict.Dict(Int, codec.Codec),
  max_rows: Int,
  timeout: Int,
) -> Result(
  #(connection.ExtendedQueryResult, connection.ConnectionState),
  error.Error,
)

Fetch all rows in chunks of max_rows and return them together. Prefer fold for large results; this collects everything in memory.