lql-spec.md

Lambda Query Language (Lql) Spec (v0.1)

Overview

Lambda Query Language (Lql) is a functional–pipeline–style DSL that transpiles to procedural SQL or pure SQL for popular RDBMSs.

Pipeline syntax

Chained operations using |>:

table |> join(other, on = …) |> filter(…) |> select(…) |> insert(…)

Constructs

Feature	Description
let name = expr	Bind an expression to a name
Identifiers	Tables, columns, or bound names
Function calls	join(table, on=cond)
Pipelines	`table	> func	> func`
Arguments	Positional or named (on=…)
Literals	'string', 123

IN List Predicates [LQL-PREDICATE-IN-LIST]

Filter predicates may use expr in (literal, literal, ...) to express membership in a non-empty literal list. Pipeline filter bodies, including exists(table |> filter(fn(row) => ...)), must emit SQL IN (...) for the target platform. This supports compact role-membership predicates such as m.role in ('owner', 'admin') without expanding to OR chains.

Futures:

join(table2, on = …)
filter(fn(row) => …)
select(cols…)
union (this contains a LIST of select statements)
insert(target_table)
group_by(cols…)
order_by(cols…, dir)
limit(n)

Supported Functions

Function	Purpose
join(table, on=…)	SQL JOIN
filter(fn(row)=>…)	SQL WHERE
map(fn(row)=>…)	SQL loop or SELECT transform
select(cols…)	SQL SELECT
insert(target)	SQL INSERT INTO … SELECT …
union(other)	SQL UNION
range(a,b)	generates a range

Output

• Target SQL dialect chosen at transpilation (postgres, mysql, sqlserver, etc.)
• Defaults to PostgreSQL if not specified.

Identifier Casing

All identifiers (table names, column names) are case-insensitive and transpile to lowercase in generated SQL. This is a fundamental design rule that ensures LQL works identically across all database platforms.

• LQL source may use any casing: fhir_Patient.GivenName, fhir_patient.givenname, FHIR_PATIENT.GIVENNAME are all equivalent
• Transpiled SQL always emits unquoted lowercase identifiers
• DDL generators (Migration tool) always create lowercase identifiers
• Never quote identifiers in generated SQL — quoting preserves case and breaks cross-platform compatibility
• Column names in YAML schemas may use PascalCase for readability; DDL generators lowercase them automatically

This guarantees portability:

• PostgreSQL: unquoted identifiers fold to lowercase
• SQLite: identifiers are case-insensitive
• SQL Server: identifiers are case-insensitive (default collation)

Validation Rules

Identifier Validation

• Numeric Start: Identifiers cannot start with numbers (e.g., 123table is invalid)
• Undefined Variables: Identifiers containing underscores that appear as pipeline bases are treated as undefined variables and result in syntax errors
  • Invalid: undefined_variable |> select(name) → "Syntax error: Undefined variable"
  • Valid: users |> select(name) → Simple table names without underscores are allowed

Error Handling

The parser performs semantic validation during the parsing phase:

• Identifiers starting with digits trigger "Syntax error: Identifier cannot start with a number"
• Undefined variables (identifiers with underscores used as pipeline bases) trigger "Syntax error: Undefined variable"