SELECT

Changes the selected database.

Browse all commands · Upstream source documentation

Reference field	Value
Canonical name	SELECT
Catalog group	Connection commands
Upstream since	1.0.0 — upstream Redis/module version, not an ffkv release
Pinned catalog	Redis 8.10.0

Syntax

SELECT index

ffkv behavior and limits

Connection state, selected database, authentication and protocol negotiation belong to the same persistent connection. RESP2 is the default; HELLO 3 selects RESP3. Streamed/unknown-length RESP3 frames are not supported.

Source: README.md:96–120, 391–395; tests/bdd/features/connections.feature.

All requests share the 8 MiB framing/1,024-argument ingress limit; normal RESP replies have 64 MiB wire/logical budgets with bounded nesting/value counts. Management and Lua origins impose smaller budgets. These are not a process RSS cap. Catalog inclusion is not exhaustive option or wire-format parity. See limits and compatibility.

Upstream metadata

The following fields come from the pinned Redis metadata, not measured ffkv performance or an assertion that ffkv enforces every upstream flag. Running COMMAND INFO/COMMAND DOCS describe the current engine.

Upstream Redis complexity: O(1)

Upstream arity: 2 (includes the command name; a negative number is a minimum).

Command flags: LOADING, STALE, FAST.

ACL categories: CONNECTION.

Argument structure

Argument	Type	Constraints / metadata
index	integer	Required

Additional pinned upstream metadata

{
  "group": "connection",
  "since": "1.0.0"
}

Metadata source · Local snapshot: src/command_metadata.json, key select.

BDD coverage and source examples

These are source observations, not a test run performed by this documentation build. A tag identifies scenario intent; an extracted vector identifies a command invocation, which may intentionally produce an error. Scenarios may require setup, multiple connections, persistence, cluster nodes or native-module fixtures.

• Database-local flush never removes another database — tests/bdd/features/catalog.feature:92; invocation observed.
• Swapping logical databases preserves values TTLs and recovery — tests/bdd/features/catalog.feature:170; invocation observed.
• Disposable debugging restores an absent cross-database destination (Scenario Outline) — tests/bdd/features/client_control_repair.feature:247; invocation observed.
• Client inspection reflects real metadata and the selected database with scoped ID filtering — tests/bdd/features/connections.feature:137; command tag and invocation observed.
• Database selection persists per connection without leaking writes to another database — tests/bdd/features/connections.feature:195; command tag and invocation observed.
• RESET clears subscriptions, database, names, protocol and tracking without closing the connection — tests/bdd/features/connections.feature:686; invocation observed.
• Tracking shares Redis key names across databases and FLUSHDB invalidates cached results — tests/bdd/features/connections.feature:849; command tag and invocation observed.
• Copy across databases replaces only when requested and detaches hash values and field deadlines — tests/bdd/features/generic.feature:5; invocation observed.
• Move respects destination collisions and transfers a hash with its deadline to another database — tests/bdd/features/generic.feature:768; invocation observed.
• Search metadata cannot be created outside database zero — tests/bdd/features/search.feature:1014; invocation observed.
• Swapping database zero reconciles search documents without replacing schemas or aliases — tests/bdd/features/search.feature:1381; invocation observed.
• Memory usage inside EXEC observes the database selected by a preceding queued command — tests/bdd/features/transactions_runtime.feature:169; command tag and invocation observed.
• Memory statistics distinguish allocated bytes from actual live keys across databases — tests/bdd/features/transactions_runtime.feature:211; invocation observed.

Extracted command vectors

The following JSON arrays are the test harness’s argument vectors, not shell commands. Numeric arguments are converted by the harness; objects of the form {"base64":"…"} represent decoded binary bytes, not a literal JSON command argument. Preserve scenario setup and connection ordering. See the CLI guide for shell quoting and binary stdin. No reply is invented or inferred.

Copy across databases replaces only when requested and detaches hash values and field deadlines — tests/bdd/features/generic.feature:19 (I execute:)

[
  "SELECT",
  1
]

Next source assertion: the reply equals:

"OK"

Client inspection reflects real metadata and the selected database with scoped ID filtering — tests/bdd/features/connections.feature:155 (client “named” executes:)

[
  "SELECT",
  "2"
]

Next source assertion: the reply equals:

"OK"

Move respects destination collisions and transfers a hash with its deadline to another database — tests/bdd/features/generic.feature:770 (the following commands succeed:)

[
  "SELECT",
  2
]