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0.4.0-rc.7 Jun 13, 2024
0.4.0-rc.4 Apr 19, 2024
0.4.0-rc.3 Mar 7, 2024
0.3.4 Nov 10, 2023
0.0.2 Jun 11, 2022

#111 in Data structures

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Used in mock-store




modql is a set of types and utilities designed to structurally express model query filters (e.g., $eq: .. $startsWith: .., $containsIn: [..]) and list options (e.g., offset, limit, order_bys). These can be easily represented in JSON.

In essence, it offers a MongoDB-like filter syntax that is storage-agnostic, has built-in support for sea-query, and can be expressed either in JSON or Rust types.

RECOMMENDATION: It is recommended to use 0.4.0-rc.x at this point as it has significant changes and is relatively stable. We are just waiting for sea-query 0.31 to release to publish modql v0.4.0.

IMPORTANT: v0.4.0, currently in rc, includes significant refactoring (retaining the same functionalities, just with cleaner naming and decoupled from sea-query) to allow derive(Fields) to provide field_names and field_refs without the need for the with-sea-query feature.

For more information, see MIGRATION-v03x-v04x.md.

Quick Overview

/// This is the model entity, annotated with Fields.
#[derive(Debug, Clone, modql::field::Fields, FromRow, Serialize)]
pub struct Task {
    pub id: i64,
    pub project_id: i64,

    pub title: String,
    pub done: bool,

/// This is a Filter, with the modql::filter::OpVals... properties
#[derive(modql::filter::FilterNodes, Deserialize, Default, Debug)]
pub struct TaskFilter {
    project_id: Option<OpValsInt64>,
    title: Option<OpValsString>,
    done: Option<OpValsBool>,

// -- Parsing JSON representation to TaskFilter
// This condition requires all of these rules to match (AND).
let list_filter: TaskFilter = serde_json::from_value(json! ({
    "project_id": 123,
    "title": {"$startsWith": "Hello", "$contains": "World"} ,

// -- modql ListOptions
let list_options: modql::filter::ListOptions =
    serde_json::from_value(json! ({
        "offset": 0,
        "limit": 2,
        "order_bys": "!title" // ! for descending
// -- Building a sea-query select query with those condition
// Convert the TaskFilter into sea-query condition
let cond: sea_query::Condition = filter.try_into()?;
let mut query = sea_query::Query::select();

// Select only the columns corresponding to the task type.
// This is determined by the modql::field::Fields annotation.

// Add the condition from the filter

// Apply the list options
list_options.apply_to_sea_query(&mut query);

// and execute query
let (sql, values) = query.build_sqlx(PostgresQueryBuilder);
let entities = sqlx::query_as_with::<_, E, _>(&sql, values)

This crate is instrumental for JSON-RPC or other types of model APIs (e.g., the joql pattern).

IMPORTANT v0.3.x represents the new version of modql, featuring the with-sea-query feature set. It is utilized in the rust10x web-app production code blueprint Episode 02. This version is somewhat incompatible with v0.2.x, mainly due to module reorganization. If you are using the rust10x/awesomeapp desktop app, please stick with v0.2.x for the time being. I plan to upgrade the codebase to v0.3.x soon.


OpVal[Type] Conditional Operators

OpVal[Type] is a filter unit that allows the expression of an operator on a given value for a specified type.

The corresponding OpVals[Type], with an "s", is typically used in filter properties, as it permits multiple operators for the same field.

The basic JSON representation of an OpVal[Type] follows the {field_name: {$operator1: value1, $operator2: value2}} format. For example:

    "title": {"$startsWith": "Hello", "$contains": "World"} 

This expresses the conditions that both "startsWith" and "contains" must be met.

The following tables show the list of possible operators for each type.

OpValString Operators

Operator Meaning Example
$eq Exact match with one value {name: {"$eq": "Jon Doe"}} same as {name: "Jon Doe"}
$in Exact match with within a list of values (or) {name: {"$in": ["Alice", "Jon Doe"]}}
$not Exclude any exact match {name: {"$not": "Jon Doe"}}
$notIn Exclude any exact withing a list {name: {"$notIn": ["Jon Doe"]}}
$contains For string, does a contains {name: {"$contains": "Doe"}}
$containsAny For string, match if contained in any of items {name: {"$containsAny": ["Doe", "Ali"]}}
$containsAll For string, match if all items are in the src {name: {"$containsAll": ["Hello", "World"]}}
$notContains Does not contain {name: {"$notContains": "Doe"}}
$notContainsAny Does not call any of (none is contained) {name: {"$notContainsAny": ["Doe", "Ali"]}}
$startsWith For string, does a startsWith {name: {"$startsWith": "Jon"}}
$startsWithAny For string, match if startsWith in any of items {name: {"$startsWithAny": ["Jon", "Al"]}}
$notStartsWith Does not start with {name: {"$notStartsWith": "Jon"}}
$notStartsWithAny Does not start with any of the items {name: {"$notStartsWithAny": ["Jon", "Al"]}}
$endsWith For string, does and end with {name: {"$endsWithAny": "Doe"}}
$endsWithAny For string, does a contains (or) {name: {"$endsWithAny": ["Doe", "ice"]}}
$notEndsWith Does not end with {name: {"$notEndsWithAny": "Doe"}}
$notEndsWithAny Does not end with any of the items {name: {"$notEndsWithAny": ["Doe", "ice"]}}
$lt Lesser Than {name: {"$lt": "C"}}
$lte Lesser Than or = {name: {"$lte": "C"}}
$gt Greater Than {name: {"$gt": "J"}}
$gte Greater Than or = {name: {"$gte": "J"}}
$null If the value is null {name: {"$null": true}}

OpValInt32, OpValInt64, OpValFloat64 Operators

Operator Meaning Example
$eq Exact match with one value {age: {"$eq": 24}} same as {age: 24}
$in Exact match with within a list of values (or) {age: {"$in": [23, 24]}}
$not Exclude any exact match {age: {"$not": 24}}
$notIn Exclude any exact withing a list {age: {"$notIn": [24]}}
$lt Lesser Than {age: {"$lt": 30}}
$lte Lesser Than or = {age: {"$lte": 30}}
$gt Greater Than {age: {"$gt": 30}}
$gte Greater Than or = {age: {"$gte": 30}}
$null If the value is null {name: {"$null": true}}

OpValBool Operators

Operator Meaning Example
$eq Exact match with one value {dev: {"$eq": true}} same as {dev: true}
$not Exclude any exact match {dev: {"$not": false}}
$null If the value is null {name: {"$null": true}}

More Info

  • modql::filter - Delivers a declarative structure that can be deserialized from JSON.
  • modql::field - Provides a method get field information on a struct. The with-sea-query feature add sea-query compatible data structure from standard structs and derive.

#[derive(modql::field::Fields) provide the following

  • Task::field_names() returns the property names of the struct. It can be overridden with the #[field(name="another_name")] property attribute.
  • Task::field_refs() returns FieldRef { name: &'static str, rel: Option<&'static str>} for the properties. rel acts like the table name. It can be set as #[modql(rel="some_table_name")] at the struct level, or #[field(rel="special_rel_name")] at the field level.

When compiled with the with-sea-query feature, these additional functions are available on the struct:

  • Task::sea_column_refs() -> Vec<ColumnRef>: Constructs sea-query select queries (with rel as the table, and name as the column name).
  • Task::sea_idens() -> Vec<DynIden>: Constructs sea-query select queries, suited for simpler cases. (similar to ::field_names() but returns the sea-query DynIden).
  • task.all_sea_fields().for_sea_insert() -> (Vec<DynIden>, Vec<SimpleExpr>): Used for sea-query inserts.
  • task.all_sea_fields().for_sea_update() -> impl Iterator<Item = (DynIden, SimpleExpr)>: Used for sea-query updates.

Additionally, it offers:

  • task.not_none_fields(): Operates similarly to the above, but only for fields where their Option is not None.

Rust types

On the Rust side, this can be expressed like this:

pub type Result<T> = core::result::Result<T, Error>;
pub type Error = Box<dyn std::error::Error>; // For early dev.
use modql::filter::{FilterGroups, FilterNode, OpValtring};

fn main() -> Result<()> {
    let filter_nodes: Vec<FilterNode> = vec![
            OpValtring::ContainsAny(vec!["Hello".to_string(), "welcome".to_string()]),
        ("done", true).into(),
    let filter_groups: FilterGroups = filter_nodes.into();



A Model or Store layer can take the filter_groups and serialize them into their DSL (e.g., SQL for databases).

The Filter structure is as follows:

  • FilterGroups is the top level and consists of multiple FilterGroup elements. FilterGroup elements are intended to be executed with an OR operation between them.
  • Each FilterGroup contains a vector of FilterNode elements, which are intended to be executed with an AND operation.
  • FilterNode contains a rel (not used yet), name which represents the property name from where the value originates, and a Vec<OpVal>, representing the Operator Value.
  • OpVal is an enum for type-specific OpVal[Type] entities, such as OpValString that holds the specific operation for that type along with the associated pattern value.

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