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Validation Filter

Validation filters allow you to define validators with SQL Syntax. Every validator has a unique filter named with prefix is_, e.g. integer validator has the is_integer filter. You can chain these filters after the variable you want to validate.

For example, we can ensure the dynamic parameters id is integer type before sending queries to data warehouse.

SELECT * FROM "artists"
WHERE ConstituentID = {{ | is_required | is_integer }}

Besides dynamic parameters, we can also chain these filters after any variables. The example below validates the result of Predefined Queries before sending the second query.

{% req artist %}
SELECT * FROM "artists"
WHERE DisplayName = {{ }} LIMIT 1
{% endreq %}

SELECT * FROM "artworks"
WHERE ConstituentID = {{ artist.value()[0].ConstituentID | is_required | is_integer }}

Set the arguments of validators

We could use Python's keyword-style arguments the configure the arguments of validators. For example, if we want to add integer validator with range [0, 100] on dynamic parameter age:

WHERE age = {{ context.params.age | integer(min=0, max=100) }}

You can use dynamic arguments as well, the following example uses a predefined query to get all the classes, and puts it into the enum validator.

{% req classification %}
SELECT Classification FROM artworks GROUP BY Classification;
{% endreq %}

{# Push the classes into classes array #}
{% set classes = [] %}
{% for c in classification.value() %}
{% set temp = classes.push(c.Classification) %}
{% endfor %}

SELECT * FROM "artworks"
WHERE Classification = {{ context.params.class | is_required | is_enum(items=classes) }}

PreCheck Validation Filters

VulcanSQL optimizes your validation filters, some filters will be upgraded to PreCheck validation filter (PCVF). PCVF provides these benefits:

  1. Validations be done before executing your SQL.
    VulcanSQL evaluates the dynamic parameters before executing SQL, we won't waste any time with invalid requests.

  2. Generate rules for API document and Catalog.
    VulcanSQL extracts the PreCheck validation filters and tells other services the rules.

    SELECT * FROM "customers"
    WHERE age = {{ context.params.age | is_required | is_integer(min=18, max=100) }}

    auto generated rules on API document

Requirements of PreCheck Validation Filters


Validation filters also work well without fitting the following requirements, but VulcanSQL makes the API server better if your validation filters follow those rules.

We will continue to improve our optimizer, but the following are the criteria to be the candidate.

  1. All arguments should be static.

    ✅ | is_number(max=20)
    ❌ | is_number(max=var)
  2. Filters should be chained right after the dynamic parameters or another PCVF.

    ✅ | is_number(max=20)
    ✅ | is_required | is_number(max=20)
    ❌ | upper | is_number(max=20)
    ❌ var | is_number(max=20)
  3. Filters should not be chained on the child of dynamic parameters.

    ✅ | is_number(max=20)
    ❌ | is_number(max=20)