Struct PoolPrewarmConfig 

pub struct PoolPrewarmConfig {
    pub min_size: usize,
    pub max_size: usize,
    pub timeout_secs: Option<u64>,
    pub search_path: Option<SearchPath>,
    pub tls: PostgresTlsConfig,
    pub max_streaming_reads: Option<usize>,
    pub vector_scan: VectorScanConfig,
    pub read_replicas: Option<ReadReplicaConfig>,
}

Configuration for connection pool construction and pre-warming.

Controls the minimum guaranteed connections (pre-warmed at startup), the maximum pool ceiling, and the wait/create timeout for connection acquisition.

Example

use fraiseql_db::postgres::{PoolPrewarmConfig, PostgresTlsConfig, VectorScanConfig};

let cfg = PoolPrewarmConfig {
    min_size:      5,
    max_size:      20,
    timeout_secs:  Some(30),
    search_path:   None,
    // Mandatory: every pool site must state its transport security (#801/#824).
    tls:           PostgresTlsConfig::default(),
    // Mandatory: every pool site must state its replica topology (#407).
    read_replicas: None,
    // `None` derives a quarter of `max_size` (#958).
    max_streaming_reads: None,
    // Continue a filtered ANN scan until `k` rows survive (#1116).
    vector_scan: VectorScanConfig::default(),
};

Fields

min_size: usize

Number of connections to establish at pool creation time.

After the pool is created, min_size connections are opened eagerly so they are ready when the first request arrives. Set to 0 to disable pre-warming (lazy init — one connection from the startup health check).

max_size: usize

Maximum number of connections the pool may hold.

timeout_secs: Option<u64>

Optional timeout (in seconds) for connection acquisition and creation.

Applied to both the wait (blocked waiting for an idle connection) and create (time to open a new TCP connection to PostgreSQL) deadpool slots. When None, acquisition can block indefinitely on pool exhaustion.

search_path: Option<SearchPath>

Schema search path every connection in this pool must resolve unqualified relations against. None leaves the server default in force.

This is a pool property, not a session one: it is lowered into the PostgreSQL startup options parameter, so the server applies it while establishing each connection — including connections deadpool opens later to grow the pool, and replacements it creates after a backend dies. See SearchPath for why the session-SET alternative is unsound.

tls: PostgresTlsConfig

Transport security for every connection this pool opens.

Mandatory, and deliberately not Option: the pool used to be built with NoTls unconditionally while three separate configuration surfaces claimed to control database TLS, so each caller must now state what it wants and a new pool site cannot compile without deciding (#801, #824). Callers with no opinion pass PostgresTlsConfig::default (libpq’s prefer).

max_streaming_reads: Option<usize>

How many of this pool’s connections may be held by streaming reads at once (#958). None derives a quarter of max_size, at least 1.

A streamed read holds its connection for the whole life of the stream — for an export, that is however long the client takes to consume a table, not however long a query takes to run. Without a bound below max_size, concurrent exports can occupy every connection in the pool and ordinary requests then fail on the acquisition timeout: a feature for large reads would take the server down by being used.

The bound is not a queue-length limit. A streaming read past the bound waits for a slot, exactly as any read waits for a connection.

vector_scan: VectorScanConfig

pgvector scan behaviour for every connection this pool opens (#1116).

Defaults, via VectorScanConfig, to continuing an index scan until k rows survive a filter. pgvector’s own default stops at one bounded candidate list, which makes a filtered similarity search return fewer rows than asked for and report success — the reason this is not left to the server’s setting.

Like search_path it is lowered into the startup packet, so it reaches every connection the pool opens later, and it is inert on a database without pgvector.

read_replicas: Option<ReadReplicaConfig>

Read replicas for this pool set, or None for a single-primary adapter.

Like tls, this is a mandatory decision at every pool site: replica pools are built from this same config — the same search_path, the same tls, the same sizing — so tenant isolation and transport security cannot silently differ between the primary and a replica (#809 generalised: isolation is a property of how every pool’s connections are made). See ReadReplicaConfig for the routing and consistency rules (#407).

Trait Implementations

impl Clone for PoolPrewarmConfig

fn clone(&self) -> PoolPrewarmConfig

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for PoolPrewarmConfig

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.