slonik-interceptor-query-cache


Caches Slonik query results.

Usage

Query cache interceptor is initialized using a custom storage service. The Example Usage documentation shows how to create a compatible storage service using node-cache.

Which queries are cached is controlled using cache attributes. Cache attributes are comments starting with -- @cache- prefix. Only queries with cache attributes are cached (see Cache attributes)

Behavior

* Does not cache queries inside of a transaction.

Cache attributes

#### @cache-ttl

|Required|Format|Default|
|---|---|---|
|Yes|/^d+$/|N/A|

Number (in seconds) to cache the query for.

#### @cache-key

|Required|Format|Default|
|---|---|---|
|No|/^[$A-Za-z0-9\-_:]+$/|$bodyHash:$valueHash|

Cache key that uniquely identifies the query.

If present, $bodyHash is substituted with the hash of the query (comments and white-spaces are stripped before hashing the query).

If present, $valueHash is substituted with the hash of the parameter values.

#### @cache-discard-empty

|Required|Format|Default|
|---|---|---|
|No|/^(false\|true)$/|false|

If set to true, then storage.set is not invoked when query produces no results.

$3

This example shows how to create a compatible storage service using node-cache.

``js
import NodeCache from 'node-cache';
import {
createPool
} from 'slonik';
import {
createQueryCacheInterceptor
} from 'slonik-interceptor-query-cache';

const nodeCache = new NodeCache({
checkperiod: 60,
stdTTL: 60,
useClones: false,
});

const pool = await createPool('postgres://', {
interceptors: [
createQueryCacheInterceptor({
storage: {
get: (query, cacheAttributes) => {
// Returning null results in the query being executed.
return cache.get(cacheAttributes.key) || null;
},
set: (query, cacheAttributes, queryResult) => {
cache.set(cacheAttributes.key, queryResult, cacheAttributes.ttl);
},
},
}),
]
});
`

These are example queries:

`ts
// Caches the query results based on a combination of the query hash and the parameter value hash.
await connection.any(sql
-- @cache-ttl 60
SELECT
id,
code_alpha_2
FROM country
WHERE
code_alpha_2 = ${countryCode}
);

// Does not cache the result when query produces no results.
await connection.any(sql
-- @cache-ttl 60
-- @cache-discard-empty true
SELECT
id,
code_alpha_2
FROM country
WHERE
code_alpha_2 = ${countryCode}
);

// Caches the query results based only on the parameter value hash.
await connection.any(sql
-- @cache-ttl 60
-- @cache-key $bodyHash
SELECT
id,
code_alpha_2
FROM country
WHERE
code_alpha_2 = ${countryCode}
);

// Caches the query results using 'foo' key.
await connection.any(sql
-- @cache-ttl 60
-- @cache-key foo
SELECT
id,
code_alpha_2
FROM country
WHERE
code_alpha_2 = ${countryCode}
);
``