Atlas Schema Rule

predicate

A predicate is composed of multiple condition blocks, operators, and quantifiers. A condition can be applied to one or more attributes of the object, such as checking column nullability and type. Additionally, a condition can be negated, combined with other conditions using logical operators, and quantified to check if the condition holds for all or some attributes.

predicate table

The predicate table consists of a set of condition blocks that apply to a table. The block has the following attributes:

Attribute	Description
name	The name of the table. Supports the eq, eq_fold, contains, contains_fold, ne, in, and match operators for comparison.
comment	The comment of the table. Supports the eq, eq_fold, contains, contains_fold, ne, in, and match operators for comparison.
self	The table itself. Supports the eq and ne operators for comparison.
primary_key	The primary key of the table. Can be checked using the condition or predicate attribute.
schema	The schema of the table. Can be checked using the condition or predicate attribute.

schema.rule.hcl

predicate "table" "not_audit" {
  not {
    name {
      match = ".+_audit$"
    }
  }
}

predicate "table" "has_sibling_audit" {
  schema {
    predicate = predicate.schema.has_table
    vars = {
      has_table = "${self.name}_audit"
    }
  }
}

predicate "schema" "has_table" {
  variable "table_name" {
    type = string
  }
  any {
    table {
      condition = self.name == var.table_name
    }
  }
}

Driver specific attributes:

PostgreSQL

Attribute	Description
row_security_enabled	The row security status of the table. Supports the eq and ne operators for comparison.
row_security_enforced	The row security enforcement status of the table. Supports the eq and ne operators for comparison.

SQLite

Attribute	Description
strict	The strict mode status of the table. Supports the eq and ne operators for comparison.
without_rowid	The without rowid status of the table. Supports the eq and ne operators for comparison.

In addition to the or, and, and not logical operators, the block supports the following quantifiers for child objects:

• any: Checks if the condition holds for at least one child object.
• all: Checks if the condition holds for all child objects.
• exists: Checks if the condition holds for at least one child object.
• count: Checks if the condition holds for a specific number of child objects.

The child objects can be of the following types:

Type	Description
column	A column of the table.
index	An index of the table.
foreign_key	A foreign key of the table.
check	A check constraint of the table.
trigger	A trigger of the table.
attr	An attribute of the table.
policy (PostgreSQL)	A policy of the table.

schema.rule.hcl

predicate "table" "has_timestamp_columns" {
  any {
    column {
      predicate = predicate.column.not_null
      vars = {
        name = "created_at"
        type = "timestamp"
      }
    }
  }
}

predicate column

The predicate column consists of a set of condition blocks that apply to a column. The block has the following attributes:

Attribute	Description
null	The nullability of the column. Supports the eq and ne operators for comparison.
name	The name of the column. Supports the eq, eq_fold, contains, contains_fold, ne, in, and match operators for comparison.
type	The data type of the column. Supports the eq, eq_fold, contains, contains_fold, ne, in, and match operators for comparison.
default	The default value of the column. Supports the eq, eq_fold, contains, contains_fold, ne, in, and match operators for comparison.
comment	The comment of the column. Supports the eq, eq_fold, contains, contains_fold, ne, in, and match operators for comparison.
primary_key	The primary key status of the column. Supports the eq and ne operators for comparison.
self	The column itself. Supports the eq and ne operators for comparison.

predicate "column" "not_null_or_have_default" {
  or {
    default {
      ne = null
    }
    null {
      eq = false
    }
  }
}

In addition to the or, and, and not logical operators, the block supports the following quantifiers for child objects:

• any: Checks if the condition holds for at least one child object.
• all: Checks if the condition holds for all child objects.
• exists: Checks if the condition holds for at least one child object.
• count: Checks if the condition holds for a specific number of child objects.

predicate schema

The predicate schema consists of a set of condition blocks that apply to a schema. The block has the following attributes:

Attribute	Description
name	The name of the schema. Supports the eq, eq_fold, contains, contains_fold, ne, in, and match operators for comparison.
comment	The comment of the schema. Supports the eq, eq_fold, contains, contains_fold, ne, in, and match operators for comparison.
self	The schema itself. Supports the eq and ne operators for comparison.

In addition to the or, and, and not logical operators, the block supports the following quantifiers for child objects:

• any: Checks if the condition holds for at least one child object.
• all: Checks if the condition holds for all child objects.
• exists: Checks if the condition holds for at least one child object.
• count: Checks if the condition holds for a specific number of child objects.

The child objects can be of the following types:

Type	Description
table	A table in the schema.
view	A view in the schema.
attr	An attribute of the schema.
function	A function in the schema.
procedure	A procedure in the schema.
attr	An attribute of the table.
policy (PostgreSQL)	A policy of the table.

schema.rule.hcl

predicate "schema" "has_tenant_policy" {
  exists {
    policy {
      predicate = predicate.policy.tenant
    }
  }
}

predicate view

The predicate view consists of a set of condition blocks that apply to a view. The block has the following attributes:

Attribute	Description
name	The name of the view. Supports the eq, eq_fold, contains, contains_fold, ne, in, and match operators for comparison.
query	The query of the view. Supports the eq, eq_fold, contains, contains_fold, ne, in, and match operators for comparison.
comment	The comment of the view. Supports the eq, eq_fold, contains, contains_fold, ne, in, and match operators for comparison.
self	The view itself. Supports the eq and ne operators for comparison.

schema.rule.hcl

predicate "view" "check_option" {
  variable "value" {
    type = string
  }
  check_option {
    eq_fold = var.value
  }
}

rule "schema" "view-check-option" {
  description = "require all views to have a specific check option"
  view {
    assert {
      predicate = predicate.view.check_option
      vars = {
        value = "CASCADED"
      }
      message = "view \"${self.name}\" must have check option CASCADED"
    }
  }
}

Driver specific attributes:

PostgreSQL

Attribute	Description
security_barrier	Supports the eq and ne operators for comparison.
security_invoker	Supports the eq and ne operators for comparison.
security_invoker	Supports the eq and ne operators for comparison.

MySQL

Attribute	Description
security	Supports the eq, eq_fold, contains, contains_fold, ne, in, and match operators for comparison.

In addition to the or, and, and not logical operators, the block supports the following quantifiers for child objects:

• any: Checks if the condition holds for at least one child object.
• all: Checks if the condition holds for all child objects.
• exists: Checks if the condition holds for at least one child object.
• count: Checks if the condition holds for a specific number of child objects.

The child objects can be of the following types:

Type	Description
column	A column of the view.
index	An index of the view.
trigger	A trigger of the view.
attr	An attribute of the view.

predicate index

The predicate index consists of a set of condition blocks that apply to an index. The block has the following attributes:

Attribute	Description
name	The name of the index. Supports the eq, eq_fold, contains, contains_fold, ne, in, and match operators for comparison.
comment	The comment of the index. Supports the eq, eq_fold, contains, contains_fold, ne, in, and match operators for comparison.
unique	Supports the eq and ne operators for comparison.

schema.rule.hcl

predicate "index" "type" {
  variable "type" {
    type = string
  }
  type {
    eq = var.type
  }
}

rule "schema" "all-indexes-btree" {
  description = "Require all indexes to be BTREE."
  table {
    index {
      assert {
        predicate = predicate.index.type
        vars      = { type = "BTREE" }
        message   = "Table ${self.table.name} index ${self.name} must be BTREE"
      }
    }
  }
}

Driver specific attributes:

PostgreSQL

Attribute	Description
type	Supports the eq, eq_fold, contains, contains_fold, ne, in, and match operators for comparison.
where	Supports the eq, eq_fold, contains, contains_fold, ne, in, and match operators for comparison.
nulls_distinct	Supports the eq and ne operators for comparison.

MySQL

Attribute	Description
type	Supports the eq, eq_fold, contains, contains_fold, ne, in, and match operators for comparison.

In addition to the or, and, and not logical operators, the block supports the following quantifiers for child objects:

• any: Checks if the condition holds for at least one child object.
• all: Checks if the condition holds for all child objects.
• exists: Checks if the condition holds for at least one child object.
• count: Checks if the condition holds for a specific number of child objects.

The child objects can be of the following types:

Type	Description
part	A part of the index (e.g., column or an expression).
attr	An attribute of the index.

schema.rule.hcl

predicate "index" "max_length_parts" {
  variable "len" {
    type = number
  }
  all {
    part {
      predicate = predicate.index_part.max_length
      vars      = { len = var.len }
    }
  }
}

predicate "index_part" "max_length" {
  variable "len" {
    type = number
  }
  or {
    prefix {
      eq = null
    }
    prefix {
      le = var.len
    }
  }
}

predicate index_part

The predicate index_part consists of a set of condition blocks that apply to an index/key part (e.g., a column or an expression together with its attributes). Each block includes the following attributes:

Attribute	Description
columm	Not-empty if the index-part is set on a column. Supports the eq, eq_fold, contains, contains_fold, ne, in, and match operators for comparison.
expr	Not-empty if the index-part is set on an expression. Supports the eq, eq_fold, contains, contains_fold, ne, in, and match operators for comparison.
desc	Supports the eq and ne operators for comparison.

schema.rule.hcl

predicate "index_part" "max_length" {
  variable "len" {
    type = number
  }
  or {
    prefix {
      eq = null
    }
    prefix {
      le = var.len
    }
  }
}

Driver specific attributes:

MySQL

Attribute	Description
prefix	Not-zero if the index-part was set on a column prefix. Supports the eq, ne, lt, le, gt, and ge operators for comparison.

predicate check

The predicate check consists of a set of condition blocks that apply to a check constraint. Each block includes the following attributes:

Attribute	Description
name	Supports the eq, eq_fold, contains, contains_fold, ne, in, and match operators for comparison.
expr	Supports the eq, eq_fold, contains, contains_fold, ne, in, and match operators for comparison.
comment	Supports the eq, eq_fold, contains, contains_fold, ne, in, and match operators for comparison.

predicate foreign_key

The predicate foreign_key consists of a set of condition blocks that apply to a foreign key constraint. Each block includes the following attributes:

Attribute	Description
name	Supports the eq, eq_fold, contains, contains_fold, ne, in, and match operators for comparison.
comment	Supports the eq, eq_fold, contains, contains_fold, ne, in, and match operators for comparison.
on_update	Supports the eq, eq_fold, contains, contains_fold, ne, in, and match operators for comparison.
on_delete	Supports the eq, eq_fold, contains, contains_fold, ne, in, and match operators for comparison.
table	Can be checked using the condition or predicate attribute.
ref_table	Can be checked using the condition or predicate attribute.

schema.rule.hcl

predicate "foreign_key" "on_delete_cascade" {
  on_delete {
    eq = "CASCADE"
  }
}

In addition to the or, and, and not logical operators, the block supports the following quantifiers for child objects (columns, ref-columns, and attributes):

• any: Checks if the condition holds for at least one child object.
• all: Checks if the condition holds for all child objects.
• exists: Checks if the condition holds for at least one child object.
• count: Checks if the condition holds for a specific number of child objects.

The child objects can be of the following types:

Type	Description
column	A column of the foreign key.
ref_column	A column of the referenced table.
attr	An attribute of the foreign key.

schema.rule.hcl

predicate "foreign_key" "on_delete_cascade" {
  on_delete {
    eq = "CASCADE"
  }
  all {
    ref_column {
      predicate = predicate.column.is_pk
    }
  }
}

predicate "column" "is_pk" {
  primary_key {
    eq = true
  }
}

rule "schema" "fk-action-cascade" {
  description = "All foreign keys must reference primary keys of the target table and use ON DELETE CASCADE"
  table {
    foreign_key {
      assert {
        predicate = predicate.foreign_key.on_delete_cascade
        message   = "foreign key ${self.name} must reference primary key of target table and use ON DELETE CASCADE"
      }
    }
  }
}

predicate trigger

The predicate trigger consists of a set of condition blocks that apply to a trigger. Each block includes the following attributes:

Attribute	Description
name	Supports the eq, eq_fold, contains, contains_fold, ne, in, and match operators for comparison.
for	Supports the eq, eq_fold, contains, contains_fold, ne, in, and match operators for comparison.
comment	Supports the eq, eq_fold, contains, contains_fold, ne, in, and match operators for comparison.
body	Supports the eq, eq_fold, contains, contains_fold, ne, in, and match operators for comparison.
table	Can be checked using the condition or predicate attribute.
view	Can be checked using the condition or predicate attribute.

Driver specific attributes:

PostreSQL

Attribute	Description
deferrable	Supports the eq and the ne operators for comparison.
initially_deferred	Supports the eq and the ne operators for comparison.

predicate function

The predicate function consists of a set of condition blocks that apply to a function. Each block includes the following attributes:

Attribute	Description
name	Supports the eq, eq_fold, contains, contains_fold, ne, in, and match operators for comparison.
lang	Supports the eq, eq_fold, contains, contains_fold, ne, in, and match operators for comparison.
return	Supports the eq, eq_fold, contains, contains_fold, ne, in, and match operators for comparison.
comment	Supports the eq, eq_fold, contains, contains_fold, ne, in, and match operators for comparison.
body	Supports the eq, eq_fold, contains, contains_fold, ne, in, and match operators for comparison.
schema	Can be checked using the condition or predicate attribute.

schema.rule.hcl

predicate "function" "match_name" {
  variable "pattern" {
    type = string
  }
  name {
    match = var.pattern
  }
}

Driver specific attributes:

PostreSQL

Attribute	Description
leakproof	Supports the eq and the ne operators for comparison.
strict	Supports the eq and the ne operators for comparison.
parallel	Supports the eq, eq_fold, contains, contains_fold, ne, in, and match operators for comparison.
security	Supports the eq, eq_fold, contains, contains_fold, ne, in, and match operators for comparison.
volatility	Supports the eq, eq_fold, contains, contains_fold, ne, in, and match operators for comparison.

schema.rule.hcl

predicate "function" "security_invoker" {
  security {
    eq = "INVOKER"
  }
}

MySQL

Attribute	Description
deterministic	Supports the eq and the ne operators for comparison.
security	Supports the eq, eq_fold, contains, contains_fold, ne, in, and match operators for comparison.
data_access	Supports the eq, eq_fold, contains, contains_fold, ne, in, and match operators for comparison.

schema.rule.hcl

predicate "function" "deterministic" {
  deterministic {
    eq = true
  }
}

In addition to the or, and, and not logical operators, the block supports the following quantifiers for child objects (function arguments and attributes):

• any: Checks if the condition holds for at least one child object.
• all: Checks if the condition holds for all child objects.
• exists: Checks if the condition holds for at least one child object.
• count: Checks if the condition holds for a specific number of child objects.

The child objects can be of the following types:

Type	Description
arg	An argument of the function.
attr	An attribute of the function.

predicate procedure

The predicate procedure consists of a set of condition blocks that apply to a procedure. Each block includes the following attributes:

Attribute	Description
name	Supports the eq, eq_fold, contains, contains_fold, ne, in, and match operators for comparison.
lang	Supports the eq, eq_fold, contains, contains_fold, ne, in, and match operators for comparison.
comment	Supports the eq, eq_fold, contains, contains_fold, ne, in, and match operators for comparison.
body	Supports the eq, eq_fold, contains, contains_fold, ne, in, and match operators for comparison.
schema	Can be checked using the condition or predicate attribute.

schema.rule.hcl

predicate "procedure" "is_sql" {
  lang {
    eq = "SQL"
  }
}

Driver specific attributes:

PostreSQL

Attribute	Description
security	Supports the eq, eq_fold, contains, contains_fold, ne, in, and match operators for comparison.

schema.rule.hcl

predicate "function" "security_invoker" {
  security {
    eq = "INVOKER"
  }
}

MySQL

Attribute	Description
deterministic	Supports the eq and the ne operators for comparison.
security	Supports the eq, eq_fold, contains, contains_fold, ne, in, and match operators for comparison.
data_access	Supports the eq, eq_fold, contains, contains_fold, ne, in, and match operators for comparison.

In addition to the or, and, and not logical operators, the block supports the following quantifiers for child objects (procedure arguments and attributes):

• any: Checks if the condition holds for at least one child object.
• all: Checks if the condition holds for all child objects.
• exists: Checks if the condition holds for at least one child object.
• count: Checks if the condition holds for a specific number of child objects.

The child objects can be of the following types:

Type	Description
arg	An argument of the procedure.
attr	An attribute of the procedure.

predicate arg

The predicate arg consists of a set of condition blocks that apply to a function argument. Each block includes the following attributes:

Attribute	Description
name	Supports the eq, eq_fold, contains, contains_fold, ne, in, and match operators for comparison.
type	Supports the eq, eq_fold, contains, contains_fold, ne, in, and match operators for comparison.
default	Supports the eq, eq_fold, contains, contains_fold, ne, in, and match operators for comparison.
mode	Supports the eq, eq_fold, contains, contains_fold, ne, in, and match operators for comparison.

schema.rule.hcl

predicate "arg" "not_out" {
  mode {
    ne = "OUT"
  }
}
predicate "function" "no_out_arg" {
  not {
    exists {
      arg {
        predicate = predicate.arg.not_out
      }
    }
  }
}

rule

The rule "schema" block defines a rule applied to the schema. It requires a name label and a description attribute that provides a human-readable explanation of the rule (it is used in the linting output).

When traversing a schema element, two blocks can be used: match and assert. The match block filters the elements the rule should apply to, and the assert block applies the predicate to the matched elements. If the predicate evaluates to false, an assertion is raised with the provided message attribute.

Example schema check

schema.rule.hcl

rule "schema" "disallow-circular-table-references" {
  description = "Disallow circular table references"
  schema {
    assert {
      predicate = predicate.schema.not_circular_ref
      message = "schema ${self.name} has circular table references"
    }
  }
}

Example foreign_key check

schema.rule.hcl

rule "schema" "fk-action-cascade" {
  description = "All foreign keys must reference primary keys of the target table and use ON DELETE CASCADE"
  table {
    foreign_key {
      assert {
        predicate = predicate.foreign_key.on_delete_cascade
        message   = "foreign key ${self.name} must reference primary key of target table and use ON DELETE CASCADE"
      }
    }
  }
}

Example primary_key check

schema.rule.hcl

rule "schema" "pk-column-uuid" {
  description = "require primary key columns to be of type UUID"
  table {
    primary_key {
      match {
        predicate = predicate.index.is_set
      }
      assert {
        predicate = predicate.index.uuid_columns_only
        message   = "primary key must be set on UUID columns only"
      }
    }
  }
}

Example column check

schema.rule.hcl

rule "schema" "column-pii" {
  description = "require all PII columns to have a specific comment"
  table {
    column {
      match {
        predicate = predicate.column.is_pii
      }
      assert {
        predicate = predicate.column.comment_match
        vars = {
          pattern = ".*PII.*"
        }
        message = "column ${self.name} must have a comment PII"
      }
    }
  }
}