postgres_param

Purpose

postgres_param extracts one parameter of a recorded PostgreSQL prepared statement. Pair it with a transform such as rand_string to send a new value on every replay, for example a unique email that would otherwise fail with 23505 duplicate key value violates unique constraint the second time it is inserted.

It applies only to requests, and only to recorded statement executions and the Bind messages they carry. Other RRPairs are left alone.

Usage

"type": "postgres_param",
"config": {
    "index": "3"
}

• index - the placeholder number in the statement, so 3 selects $3.

The extracted value is text, and NULL is an empty value. Parameters your client sent in binary format are decoded for common types such as integers, floats, booleans, dates, timestamps and UUIDs. When a transform writes a new value, the parameter is sent in text format, so PostgreSQL parses it for the parameter's type and converts or rejects it as it would a literal in the statement.

Example

Regenerate the email, $3, of every replayed user insert:

{
    "filters": {"filters": [{"include": true, "detectedLocation": "INSERT INTO users", "operator": "CONTAINS"}]},
    "extractor": {"type": "postgres_param", "config": {"index": "3"}},
    "transforms": [{"type": "rand_string", "config": {"pattern": "[a-z0-9]{12}@load\\.test"}}]
}

See PostgreSQL Load and Regression Testing for the full walkthrough.