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Parameters

prestd uses query string to apply filtering, sorting, paginating, and etc to api queries.

Filters

HTTP method GET

query string
Description

_page={set page number}

the api return is paged, this parameter sets which page you want

_page_size={number to return by pages}

delimits the number of records per page, default 10. Every time you specify a page size, you must include the page you are accessing.

?_select={field name 1},{field name 2}

Limit fields list on result. Comma-separated field names are whitespace-trimmed (id, name is equivalent to id,name). Values are validated — see _select field validation.

?_count={field name}

Count per field - * representation all fields

?_count_first=true

Query string _count returns a list, passing this parameter will return the first record as a non-list object, by default this parameter is set to false (return list non-object)

?_renderer=xml

Set API render syntax, supported: json (by default), xml

?_distinct=true

DISTINCT clause with SELECT

?_order={FIELD}

ORDER BY in sql query. For DESC order, use the prefix -. For multiple orders, the fields are separated by comma fieldname01,-fieldname02,fieldname03

?_groupby={FIELD}

GROUP BY in sql query, The grouper is more complicated, a topic has been created to describe how to use

?{FIELD NAME}={VALUE}

Filter by field, you can set as many query parameters as needed

?_or={CONDITION}||{CONDITION}

OR clause filtering — combine alternatives with ||. See OR clause filtering below.

Functions support

Used to perform data aggregation(grouping and selection)

name
Use in request

SUM

sum:field

AVG

avg:field

MAX

max:field

MIN

min:field

STDDEV

stddev:field

VARIANCE

variance:field

SELECT with function:

GROUP BY with function:

_select field validation (v2.3.0)

Since v2.3.0 (#1002, GHSA-qvx3-q8vx-9q3c), _select and _count values pass through a single validation gate that closes an unauthenticated SQL-injection. Each comma-separated field must be one of:

Form
Example

Wildcard

*

Identifier, optionally dotted

id, public.users.name

Colon-syntax aggregate

sum:salary, avg:rating

Pre-quoted aggregate

SUM("salary") AS "total"

Aggregates are limited to SUM, AVG, MAX, MIN, STDDEV, VARIANCE. Anything else — subselects, pg_* probing, or extra parentheses — returns 400 ErrInvalidIdentifier. _count field names are quoted in the generated SQL (, celphone → , "celphone").

For projections that need arbitrary SQL expressions, use a custom query instead.

pgvector KNN ordering and distance filtering (v2.4.0)

Since v2.4.0 (#1011), two query-parameter forms are available for vector-typed columns (requires the pgvector extension on the target database):

Parameter
Form
Example
Effect

_korder

<column>:<metric>:<vector>

_korder=embedding:l2:[1,0,0]

Orders by nearest-neighbor distance (KNN); composes with _order as an additional sort term

<column>:vecdist

<metric>:<comparison>:<vector>:<threshold>

embedding:vecdist=l2:lt:[1,0,0]:0.5

Filters rows by distance threshold

Metrics are restricted to a fixed whitelist: l2/euclidean, cosine/cos, ip/inner/dot, l1/manhattan. :vecdist comparisons are restricted to =, !=, <, <=, >, >= (non-scalar comparisons like like are rejected). The column goes through identifier validation, the vector literal round-trips through ParseFloat/FormatFloat, and the threshold is passed as a bound parameter — malformed metrics, non-numeric vector elements, oversized vectors (>16000 dims, pgvector's own limit), and dimension mismatches all return 400 rather than reaching the database unsafely.

Operators Reference Guide

The following operators are used for filtering data in queries. Each operator defines a specific matching condition that determines which records are included in the result set.

Operator
Description
Example Usage

$eq

Matches values that are equal to a specified value.

status=$eq.active

$gt

Matches values greater than a specified value.

age=$gt.25

$gte

Matches values greater than or equal to a specified value.

salary=$gte.50000

$lt

Matches values less than a specified value.

experience=$lt.5

$lte

Matches values less than or equal to a specified value.

rating=$lte.4.5

$ne

Matches values that are not equal to a specified value.

status=$ne.closed

$in

Matches any of the values specified in an array.

role=$in.admin,editor,viewer

$nin

Matches none of the values specified in an array.

department=$nin.hr,finance

$null

Matches if the field value is null.

remarks=$null

$notnull

Matches if the field value is not null.

remarks=$notnull

$true

Matches if the field value is true.

is_verified=$true

$nottrue

Matches if the field value is not true.

is_verified=$nottrue

$false

Matches if the field value is false.

is_active=$false

$notfalse

Matches if the field value is not false.

is_active=$notfalse

$like

Matches the entire string (case-sensitive).

name=$like.John%

$ilike

Matches the entire string, case-insensitive.

city=$ilike.mumbai%

$nlike

Excludes matches that cover the entire string.

email=$nlike.%@test.com

$nilike

Excludes matches, case-insensitive.

email=$nilike.%@gmail.com

$ltreelanc

Checks if left argument is an ancestor of right (or equal).

category_path=$ltreelanc.electronics

$ltreerdesc

Checks if left argument is a descendant of right (or equal).

category_path=$ltreerdesc.electronics.mobiles

$ltreematch

Checks if ltree matches lquery.

tags=$ltreematch.tech.*

$ltreematchtxt

Checks if ltree matches ltxtquery.

tags=$ltreematchtxt.smartphone & android

OR clause filtering

Use _or to combine filter conditions with OR logic without writing a custom SQL query. Available since v2.0.0-rc6, included in v2.0.0.

Each alternative is field=$operator.value using the same operators as the table above. Separate alternatives with || (double pipe). The OR group is parenthesized and AND-combined with other query parameters.

The second example matches rows where (status = 'active' OR status = 'pending') AND category = 'tech'.

Notes:

  • Empty or malformed _or values are ignored.

  • Use || to separate alternatives — not a literal OR inside values.

  • Comma-separated values within a single alternative (e.g. $in) are preserved.

Notes

  • Comma (,) is used to separate multiple values in $in and $nin operators.

  • Pattern matching operators like $like and $ilike support SQL wildcards (%, _).

  • LTree operators ($ltreelanc, $ltreerdesc, etc.) are useful for hierarchical data filtering.

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