Module: ClickhouseRuby::ActiveRecord::SchemaStatements

Included in:
ConnectionAdapter
Defined in:
lib/clickhouse_ruby/active_record/schema_statements.rb

Overview

Note:

ClickHouse schema operations differ significantly from traditional RDBMS:

  • Tables require ENGINE specification (MergeTree, etc.)

  • No SERIAL/AUTO_INCREMENT (use generateUUIDv4() or application-side IDs)

  • No ALTER TABLE ADD COLUMN migrations (use ALTER TABLE ADD COLUMN)

  • Indexes are defined at table creation time

Schema introspection and manipulation methods for ClickHouse

Provides methods to query and modify database schema through ClickHouse’s system tables (system.tables, system.columns, etc.)

Instance Method Summary collapse

Instance Method Details

#add_column(table_name, column_name, type, **options) ⇒ void

This method returns an undefined value.

Add a column to a table

Parameters:

  • table_name (String) —

    the table name

  • column_name (String) —

    the column name

  • type (Symbol, String) —

    the column type

  • options (Hash) —

    column options

Options Hash (**options):

  • :after (String) —

    add column after this column

  • :default (Object) —

    default value

  • :null (Boolean) —

    whether column is nullable

Raises:



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# File 'lib/clickhouse_ruby/active_record/schema_statements.rb', line 231

def add_column(table_name, column_name, type, **options)
  sql_type = type_to_sql(type, **options)

  # Handle nullable
  sql_type = "Nullable(#{sql_type})" if options[:null] != false && !sql_type.match?(/^Nullable/i)

  sql = "ALTER TABLE #{quote_table_name(table_name)} ADD COLUMN #{quote_column_name(column_name)} #{sql_type}"

  # Add AFTER clause if specified
  sql += " AFTER #{quote_column_name(options[:after])}" if options[:after]

  # Add DEFAULT if specified
  sql += " DEFAULT #{quote(options[:default])}" if options.key?(:default)

  execute(sql, "ADD COLUMN")
end

#add_index(table_name, column_name, **options) ⇒ void

This method returns an undefined value.

Add an index to a table ClickHouse uses data skipping indexes (minmax, set, bloom_filter, etc.)

Parameters:

  • table_name (String) —

    the table name

  • column_name (String, Array<String>) —

    the column(s) to index

  • options (Hash) —

    index options

Options Hash (**options):

  • :name (String) —

    the index name

  • :type (String) —

    the index type (minmax, set, bloom_filter, etc.)

  • :granularity (Integer) —

    the index granularity

Raises:



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# File 'lib/clickhouse_ruby/active_record/schema_statements.rb', line 305

def add_index(table_name, column_name, **options)
  columns = Array(column_name).map { |c| quote_column_name(c) }.join(", ")
  index_name = options[:name] || "idx_#{Array(column_name).join("_")}"
  index_type = options[:type] || "minmax"
  granularity = options[:granularity] || 1

  sql = "ALTER TABLE #{quote_table_name(table_name)} ADD INDEX #{quote_column_name(index_name)} (#{columns}) TYPE #{index_type} GRANULARITY #{granularity}"
  execute(sql, "ADD INDEX")
end

#change_column(table_name, column_name, type, **options) ⇒ void

This method returns an undefined value.

Change a column’s type

Parameters:

  • table_name (String) —

    the table name

  • column_name (String) —

    the column name

  • type (Symbol, String) —

    the new column type

  • options (Hash) —

    column options

Raises:



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# File 'lib/clickhouse_ruby/active_record/schema_statements.rb', line 280

def change_column(table_name, column_name, type, **options)
  sql_type = type_to_sql(type, **options)

  # Handle nullable
  sql_type = "Nullable(#{sql_type})" if options[:null] != false && !sql_type.match?(/^Nullable/i)

  sql = "ALTER TABLE #{quote_table_name(table_name)} MODIFY COLUMN #{quote_column_name(column_name)} #{sql_type}"

  # Add DEFAULT if specified
  sql += " DEFAULT #{quote(options[:default])}" if options.key?(:default)

  execute(sql, "MODIFY COLUMN")
end

#column_exists?(table_name, column_name, type = nil, **options) ⇒ Boolean

Check if a column exists

Parameters:

  • table_name (String) —

    the table name

  • column_name (String) —

    the column name

Returns:

  • (Boolean) —

    true if the column exists



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# File 'lib/clickhouse_ruby/active_record/schema_statements.rb', line 358

def column_exists?(table_name, column_name, type = nil, **options)
  sql = "    SELECT type\n    FROM system.columns\n    WHERE database = currentDatabase()\n      AND table = '\#{quote_string(table_name.to_s)}'\n      AND name = '\#{quote_string(column_name.to_s)}'\n    LIMIT 1\n  SQL\n\n  result = execute(sql, \"SCHEMA\")\n  return false if result.empty?\n\n  if type\n    # Check if type matches\n    column_type = result.first[\"type\"]\n    expected_type = type_to_sql(type, **options)\n    column_type.downcase.include?(expected_type.downcase)\n  else\n    true\n  end\nend\n"

#columns(table_name) ⇒ Array<Column>

Returns list of columns for a table

Parameters:

  • table_name (String) —

    the table name

Returns:

  • (Array<Column>) —

    list of column objects



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# File 'lib/clickhouse_ruby/active_record/schema_statements.rb', line 116

def columns(table_name)
  sql = "    SELECT\n      name,\n      type,\n      default_kind,\n      default_expression,\n      comment,\n      is_in_primary_key,\n      is_in_sorting_key,\n      is_in_partition_key\n    FROM system.columns\n    WHERE database = currentDatabase()\n      AND table = '\#{quote_string(table_name.to_s)}'\n    ORDER BY position\n  SQL\n\n  result = execute(sql, \"SCHEMA\")\n  result.map do |row|\n    new_column(\n      row[\"name\"],\n      row[\"default_expression\"],\n      fetch_type_metadata(row[\"type\"]),\n      row[\"type\"] =~ /^Nullable/i,\n      row[\"comment\"],\n    )\n  end\nend\n"

#create_database(database_name, **options) ⇒ void

This method returns an undefined value.

Create a database

Parameters:

  • database_name (String) —

    the database name

  • options (Hash) —

    database options

Options Hash (**options):

  • :if_not_exists (Boolean) —

    add IF NOT EXISTS clause

Raises:



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# File 'lib/clickhouse_ruby/active_record/schema_statements.rb', line 404

def create_database(database_name, **options)
  if_not_exists = options.fetch(:if_not_exists, false)
  sql = "CREATE DATABASE #{if_not_exists ? "IF NOT EXISTS " : ""}`#{database_name}`"
  execute(sql, "CREATE DATABASE")
end

#create_table(table_name, **options) {|TableDefinition| ... } ⇒ void

This method returns an undefined value.

Create a new table

Parameters:

  • table_name (String) —

    the table name

  • options (Hash) —

    table options

Options Hash (**options):

  • :engine (String) —

    the table engine (default: MergeTree)

  • :order_by (String) —

    ORDER BY clause for MergeTree

  • :partition_by (String) —

    PARTITION BY clause

  • :primary_key (String) —

    PRIMARY KEY clause

  • :settings (String) —

    table SETTINGS

Yields:

Raises:



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# File 'lib/clickhouse_ruby/active_record/schema_statements.rb', line 176

def create_table(table_name, **options)
  td = create_table_definition(table_name, **options)

  yield td if block_given?

  sql = schema_creation.accept(td)
  execute(sql, "CREATE TABLE")
end

#current_database ⇒ String

Get the current database name

Returns:

  • (String) —

    the database name



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# File 'lib/clickhouse_ruby/active_record/schema_statements.rb', line 384

def current_database
  result = execute("SELECT currentDatabase() AS db", "SCHEMA")
  result.first["db"]
end

#databases ⇒ Array<String>

List all databases

Returns:

  • (Array<String>) —

    list of database names



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# File 'lib/clickhouse_ruby/active_record/schema_statements.rb', line 392

def databases
  result = execute("SELECT name FROM system.databases ORDER BY name", "SCHEMA")
  result.map { |row| row["name"] }
end

#drop_database(database_name, **options) ⇒ void

This method returns an undefined value.

Drop a database

Parameters:

  • database_name (String) —

    the database name

  • options (Hash) —

    drop options

Options Hash (**options):

  • :if_exists (Boolean) —

    add IF EXISTS clause

Raises:



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# File 'lib/clickhouse_ruby/active_record/schema_statements.rb', line 417

def drop_database(database_name, **options)
  if_exists = options.fetch(:if_exists, false)
  sql = "DROP DATABASE #{if_exists ? "IF EXISTS " : ""}`#{database_name}`"
  execute(sql, "DROP DATABASE")
end

#drop_table(table_name, **options) ⇒ void

This method returns an undefined value.

Drop a table

Parameters:

  • table_name (String) —

    the table name

  • options (Hash) —

    drop options

Options Hash (**options):

  • :if_exists (Boolean) —

    add IF EXISTS clause

Raises:



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# File 'lib/clickhouse_ruby/active_record/schema_statements.rb', line 192

def drop_table(table_name, **options)
  if_exists = options.fetch(:if_exists, false)
  sql = "DROP TABLE #{if_exists ? "IF EXISTS " : ""}#{quote_table_name(table_name)}"
  execute(sql, "DROP TABLE")
end

#index_exists?(table_name, index_name) ⇒ Boolean

Check if an index exists

Parameters:

  • table_name (String) —

    the table name

  • index_name (String) —

    the index name

Returns:

  • (Boolean) —

    true if the index exists



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# File 'lib/clickhouse_ruby/active_record/schema_statements.rb', line 339

def index_exists?(table_name, index_name)
  sql = "    SELECT 1\n    FROM system.data_skipping_indices\n    WHERE database = currentDatabase()\n      AND table = '\#{quote_string(table_name.to_s)}'\n      AND name = '\#{quote_string(index_name.to_s)}'\n    LIMIT 1\n  SQL\n\n  result = execute(sql, \"SCHEMA\")\n  result.any?\nend\n"

#indexes(table_name) ⇒ Array<Hash>

Returns list of indexes for a table

Parameters:

  • table_name (String) —

    the table name

Returns:

  • (Array<Hash>) —

    list of index information



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# File 'lib/clickhouse_ruby/active_record/schema_statements.rb', line 88

def indexes(table_name)
  sql = "    SELECT\n      name,\n      type,\n      expr,\n      granularity\n    FROM system.data_skipping_indices\n    WHERE database = currentDatabase()\n      AND table = '\#{quote_string(table_name.to_s)}'\n    ORDER BY name\n  SQL\n\n  result = execute(sql, \"SCHEMA\")\n  result.map do |row|\n    {\n      name: row[\"name\"],\n      type: row[\"type\"],\n      expression: row[\"expr\"],\n      granularity: row[\"granularity\"],\n    }\n  end\nend\n"

#primary_keys(table_name) ⇒ Array<String>?

Returns the primary key columns for a table

Parameters:

  • table_name (String) —

    the table name

Returns:

  • (Array<String>, nil) —

    primary key column names or nil



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# File 'lib/clickhouse_ruby/active_record/schema_statements.rb', line 149

def primary_keys(table_name)
  sql = "    SELECT name\n    FROM system.columns\n    WHERE database = currentDatabase()\n      AND table = '\#{quote_string(table_name.to_s)}'\n      AND is_in_primary_key = 1\n    ORDER BY position\n  SQL\n\n  result = execute(sql, \"SCHEMA\")\n  keys = result.map { |row| row[\"name\"] }\n  keys.empty? ? nil : keys\nend\n"

#remove_column(table_name, column_name, _type = nil, **_options) ⇒ void

This method returns an undefined value.

Remove a column from a table

Parameters:

  • table_name (String) —

    the table name

  • column_name (String) —

    the column name

  • options (Hash) —

    options (unused)

Raises:



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# File 'lib/clickhouse_ruby/active_record/schema_statements.rb', line 255

def remove_column(table_name, column_name, _type = nil, **_options)
  sql = "ALTER TABLE #{quote_table_name(table_name)} DROP COLUMN #{quote_column_name(column_name)}"
  execute(sql, "DROP COLUMN")
end

#remove_index(table_name, options_or_column = nil, **options) ⇒ void

This method returns an undefined value.

Remove an index from a table

Parameters:

  • table_name (String) —

    the table name

  • options_or_column (Hash, String, Symbol) (defaults to: nil) —

    index name or options with :name

Raises:



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# File 'lib/clickhouse_ruby/active_record/schema_statements.rb', line 321

def remove_index(table_name, options_or_column = nil, **options)
  index_name = if options_or_column.is_a?(Hash)
                 options_or_column[:name]
               elsif options[:name]
                 options[:name]
               else
                 "idx_#{Array(options_or_column).join("_")}"
               end

  sql = "ALTER TABLE #{quote_table_name(table_name)} DROP INDEX #{quote_column_name(index_name)}"
  execute(sql, "DROP INDEX")
end

#rename_column(table_name, old_name, new_name) ⇒ void

This method returns an undefined value.

Rename a column

Parameters:

  • table_name (String) —

    the table name

  • old_name (String) —

    the current column name

  • new_name (String) —

    the new column name

Raises:



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# File 'lib/clickhouse_ruby/active_record/schema_statements.rb', line 267

def rename_column(table_name, old_name, new_name)
  sql = "ALTER TABLE #{quote_table_name(table_name)} RENAME COLUMN #{quote_column_name(old_name)} TO #{quote_column_name(new_name)}"
  execute(sql, "RENAME COLUMN")
end

#rename_table(old_name, new_name) ⇒ void

This method returns an undefined value.

Rename a table

Parameters:

  • old_name (String) —

    the current table name

  • new_name (String) —

    the new table name

Raises:



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# File 'lib/clickhouse_ruby/active_record/schema_statements.rb', line 204

def rename_table(old_name, new_name)
  sql = "RENAME TABLE #{quote_table_name(old_name)} TO #{quote_table_name(new_name)}"
  execute(sql, "RENAME TABLE")
end

#table_exists?(table_name) ⇒ Boolean

Check if a table exists

Parameters:

  • table_name (String) —

    the table name to check

Returns:

  • (Boolean) —

    true if the table exists



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# File 'lib/clickhouse_ruby/active_record/schema_statements.rb', line 53

def table_exists?(table_name)
  sql = "    SELECT 1\n    FROM system.tables\n    WHERE database = currentDatabase()\n      AND name = '\#{quote_string(table_name.to_s)}'\n    LIMIT 1\n  SQL\n\n  result = execute(sql, \"SCHEMA\")\n  result.any?\nend\n"

#tables ⇒ Array<String>

Returns list of tables in the current database

Returns:

  • (Array<String>) —

    list of table names



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# File 'lib/clickhouse_ruby/active_record/schema_statements.rb', line 20

def tables
  sql = "    SELECT name\n    FROM system.tables\n    WHERE database = currentDatabase()\n      AND engine NOT IN ('View', 'MaterializedView', 'LiveView')\n    ORDER BY name\n  SQL\n\n  result = execute(sql, \"SCHEMA\")\n  result.map { |row| row[\"name\"] }\nend\n"

#truncate_table(table_name, **_options) ⇒ void

This method returns an undefined value.

Truncate a table (delete all data)

Parameters:

  • table_name (String) —

    the table name

  • options (Hash) —

    truncate options

Raises:



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# File 'lib/clickhouse_ruby/active_record/schema_statements.rb', line 215

def truncate_table(table_name, **_options)
  sql = "TRUNCATE TABLE #{quote_table_name(table_name)}"
  execute(sql, "TRUNCATE TABLE")
end

#view_exists?(view_name) ⇒ Boolean

Check if a view exists

Parameters:

  • view_name (String) —

    the view name to check

Returns:

  • (Boolean) —

    true if the view exists



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# File 'lib/clickhouse_ruby/active_record/schema_statements.rb', line 70

def view_exists?(view_name)
  sql = "    SELECT 1\n    FROM system.tables\n    WHERE database = currentDatabase()\n      AND name = '\#{quote_string(view_name.to_s)}'\n      AND engine IN ('View', 'MaterializedView', 'LiveView')\n    LIMIT 1\n  SQL\n\n  result = execute(sql, \"SCHEMA\")\n  result.any?\nend\n"

#views ⇒ Array<String>

Returns list of views in the current database

Returns:

  • (Array<String>) —

    list of view names



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# File 'lib/clickhouse_ruby/active_record/schema_statements.rb', line 36

def views
  sql = "    SELECT name\n    FROM system.tables\n    WHERE database = currentDatabase()\n      AND engine IN ('View', 'MaterializedView', 'LiveView')\n    ORDER BY name\n  SQL\n\n  result = execute(sql, \"SCHEMA\")\n  result.map { |row| row[\"name\"] }\nend\n"