# File activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb, line 669
def add_exclusion_constraint(table_name, expression, **options)
  options = exclusion_constraint_options(table_name, expression, options)
  at = create_alter_table(table_name)
  at.add_exclusion_constraint(expression, options)

  execute schema_creation.accept(at)
end

# File activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb, line 720
def add_unique_key(table_name, column_name, **options)
  options = unique_key_options(table_name, column_name, options)
  at = create_alter_table(table_name)
  at.add_unique_key(column_name, options)

  execute schema_creation.accept(at)
end

# File activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb, line 243
def client_min_messages
  query_value("SHOW client_min_messages", "SCHEMA")
end

# File activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb, line 248
def client_min_messages=(level)
  internal_execute("SET client_min_messages TO '#{level}'")
end

# File activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb, line 195
def collation
  query_value("SELECT datcollate FROM pg_database WHERE datname = current_database()", "SCHEMA")
end

# File activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb, line 22
def create_database(name, options = {})
  options = { encoding: "utf8" }.merge!(options.symbolize_keys)

  option_string = options.each_with_object(+"") do |(key, value), memo|
    memo << case key
            when :owner
              " OWNER = \"#{value}\""
            when :template
              " TEMPLATE = \"#{value}\""
            when :encoding
              " ENCODING = '#{value}'"
            when :collation
              " LC_COLLATE = '#{value}'"
            when :ctype
              " LC_CTYPE = '#{value}'"
            when :tablespace
              " TABLESPACE = \"#{value}\""
            when :connection_limit
              " CONNECTION LIMIT = #{value}"
            else
              ""
    end
  end

  execute "CREATE DATABASE #{quote_table_name(name)}#{option_string}"
end

# File activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb, line 216
def create_schema(schema_name)
  execute "CREATE SCHEMA #{quote_schema_name(schema_name)}"
end

# File activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb, line 200
def ctype
  query_value("SELECT datctype FROM pg_database WHERE datname = current_database()", "SCHEMA")
end

# File activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb, line 180
def current_database
  query_value("SELECT current_database()", "SCHEMA")
end

# File activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb, line 185
def current_schema
  query_value("SELECT current_schema", "SCHEMA")
end

# File activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb, line 221
def drop_schema(schema_name, **options)
  execute "DROP SCHEMA#{' IF EXISTS' if options[:if_exists]} #{quote_schema_name(schema_name)} CASCADE"
end

# File activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb, line 190
def encoding
  query_value("SELECT pg_encoding_to_char(encoding) FROM pg_database WHERE datname = current_database()", "SCHEMA")
end

# File activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb, line 589
        def exclusion_constraints(table_name)
          scope = quoted_scope(table_name)

          exclusion_info = exec_query(<<-SQL, "SCHEMA")
            SELECT conname, pg_get_constraintdef(c.oid) AS constraintdef, c.condeferrable, c.condeferred
            FROM pg_constraint c
            JOIN pg_class t ON c.conrelid = t.oid
            JOIN pg_namespace n ON n.oid = c.connamespace
            WHERE c.contype = 'x'
              AND t.relname = #{scope[:name]}
              AND n.nspname = #{scope[:schema]}
          SQL

          exclusion_info.map do |row|
            method_and_elements, predicate = row["constraintdef"].split(" WHERE ")
            method_and_elements_parts = method_and_elements.match(/EXCLUDE(?: USING (?<using>\S+))? \((?<expression>.+)\)/)
            predicate.remove!(/ DEFERRABLE(?: INITIALLY (?:IMMEDIATE|DEFERRED))?/) if predicate
            predicate = predicate.from(2).to(-3) if predicate # strip 2 opening and closing parentheses

            deferrable = extract_constraint_deferrable(row["condeferrable"], row["condeferred"])

            options = {
              name: row["conname"],
              using: method_and_elements_parts["using"].to_sym,
              where: predicate,
              deferrable: deferrable
            }

            ExclusionConstraintDefinition.new(table_name, method_and_elements_parts["expression"], options)
          end
        end

# File activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb, line 521
        def foreign_keys(table_name)
          scope = quoted_scope(table_name)
          fk_info = exec_query(<<~SQL, "SCHEMA", allow_retry: true, uses_transaction: false)
            SELECT t2.oid::regclass::text AS to_table, a1.attname AS column, a2.attname AS primary_key, c.conname AS name, c.confupdtype AS on_update, c.confdeltype AS on_delete, c.convalidated AS valid, c.condeferrable AS deferrable, c.condeferred AS deferred
            FROM pg_constraint c
            JOIN pg_class t1 ON c.conrelid = t1.oid
            JOIN pg_class t2 ON c.confrelid = t2.oid
            JOIN pg_attribute a1 ON a1.attnum = c.conkey[1] AND a1.attrelid = t1.oid
            JOIN pg_attribute a2 ON a2.attnum = c.confkey[1] AND a2.attrelid = t2.oid
            JOIN pg_namespace t3 ON c.connamespace = t3.oid
            WHERE c.contype = 'f'
              AND t1.relname = #{scope[:name]}
              AND t3.nspname = #{scope[:schema]}
            ORDER BY c.conname
          SQL

          fk_info.map do |row|
            options = {
              column: Utils.unquote_identifier(row["column"]),
              name: row["name"],
              primary_key: row["primary_key"]
            }

            options[:on_delete] = extract_foreign_key_action(row["on_delete"])
            options[:on_update] = extract_foreign_key_action(row["on_update"])
            options[:deferrable] = extract_foreign_key_deferrable(row["deferrable"], row["deferred"])

            options[:validate] = row["valid"]
            to_table = Utils.unquote_identifier(row["to_table"])

            ForeignKeyDefinition.new(table_name, to_table, options)
          end
        end

# File activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb, line 559
def foreign_table_exists?(table_name)
  query_values(data_source_sql(table_name, type: "FOREIGN TABLE"), "SCHEMA").any? if table_name.present?
end

# File activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb, line 555
def foreign_tables
  query_values(data_source_sql(type: "FOREIGN TABLE"), "SCHEMA")
end

# File activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb, line 68
        def index_name_exists?(table_name, index_name)
          table = quoted_scope(table_name)
          index = quoted_scope(index_name)

          query_value(<<~SQL, "SCHEMA").to_i > 0
            SELECT COUNT(*)
            FROM pg_class t
            INNER JOIN pg_index d ON t.oid = d.indrelid
            INNER JOIN pg_class i ON d.indexrelid = i.oid
            LEFT JOIN pg_namespace n ON n.oid = t.relnamespace
            WHERE i.relkind IN ('i', 'I')
              AND i.relname = #{index[:name]}
              AND t.relname = #{table[:name]}
              AND n.nspname = #{table[:schema]}
          SQL
        end

# File activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb, line 692
def remove_exclusion_constraint(table_name, expression = nil, **options)
  excl_name_to_delete = exclusion_constraint_for!(table_name, expression: expression, **options).name

  at = create_alter_table(table_name)
  at.drop_exclusion_constraint(excl_name_to_delete)

  execute schema_creation.accept(at)
end

# File activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb, line 743
def remove_unique_key(table_name, column_name = nil, **options)
  unique_name_to_delete = unique_key_for!(table_name, column_name: column_name, **options).name

  at = create_alter_table(table_name)
  at.drop_unique_key(unique_name_to_delete)

  execute schema_creation.accept(at)
end

# File activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb, line 509
def rename_index(table_name, old_name, new_name)
  validate_index_length!(table_name, new_name)

  schema, = extract_schema_qualified_name(table_name)
  execute "ALTER INDEX #{quote_table_name(schema) + '.' if schema}#{quote_column_name(old_name)} RENAME TO #{quote_table_name(new_name)}"
end

# File activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb, line 384
def rename_table(table_name, new_name, **options)
  validate_table_length!(new_name) unless options[:_uses_legacy_table_name]
  clear_cache!
  schema_cache.clear_data_source_cache!(table_name.to_s)
  schema_cache.clear_data_source_cache!(new_name.to_s)
  execute "ALTER TABLE #{quote_table_name(table_name)} RENAME TO #{quote_table_name(new_name)}"
  pk, seq = pk_and_sequence_for(new_name)
  if pk
    idx = "#{table_name}_pkey"
    new_idx = "#{new_name}_pkey"
    execute "ALTER INDEX #{quote_table_name(idx)} RENAME TO #{quote_table_name(new_idx)}"
    if seq && seq.identifier == "#{table_name}_#{pk}_seq"
      new_seq = "#{new_name}_#{pk}_seq"
      execute "ALTER TABLE #{seq.quoted} RENAME TO #{quote_table_name(new_seq)}"
    end
  end
  rename_table_indexes(table_name, new_name)
end

# File activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb, line 63
def schema_exists?(name)
  query_value("SELECT COUNT(*) FROM pg_namespace WHERE nspname = #{quote(name)}", "SCHEMA").to_i > 0
end

# File activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb, line 205
        def schema_names
          query_values(<<~SQL, "SCHEMA")
            SELECT nspname
              FROM pg_namespace
             WHERE nspname !~ '^pg_.*'
               AND nspname NOT IN ('information_schema')
             ORDER by nspname;
          SQL
        end

# File activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb, line 238
def schema_search_path
  @schema_search_path ||= query_value("SHOW search_path", "SCHEMA")
end

# File activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb, line 230
def schema_search_path=(schema_csv)
  if schema_csv
    internal_execute("SET search_path TO #{schema_csv}")
    @schema_search_path = schema_csv
  end
end

# File activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb, line 261
def serial_sequence(table, column)
  query_value("SELECT pg_get_serial_sequence(#{quote(table)}, #{quote(column)})", "SCHEMA")
end

# File activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb, line 623
        def unique_keys(table_name)
          scope = quoted_scope(table_name)

          unique_info = exec_query(<<~SQL, "SCHEMA", allow_retry: true, uses_transaction: false)
            SELECT c.conname, c.conindid, c.condeferrable, c.condeferred
            FROM pg_constraint c
            JOIN pg_class t ON c.conrelid = t.oid
            JOIN pg_namespace n ON n.oid = c.connamespace
            WHERE c.contype = 'u'
              AND t.relname = #{scope[:name]}
              AND n.nspname = #{scope[:schema]}
          SQL

          unique_info.map do |row|
            deferrable = extract_constraint_deferrable(row["condeferrable"], row["condeferred"])

            columns = query_values(<<~SQL, "SCHEMA")
              SELECT a.attname
              FROM pg_attribute a
              WHERE a.attrelid = #{row['conindid']}
              ORDER BY a.attnum
            SQL

            options = {
              name: row["conname"],
              deferrable: deferrable
            }

            UniqueKeyDefinition.new(table_name, columns, options)
          end
        end

# File activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb, line 849
def validate_check_constraint(table_name, **options)
  chk_name_to_validate = check_constraint_for!(table_name, **options).name

  validate_constraint table_name, chk_name_to_validate
end

# File activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb, line 816
def validate_constraint(table_name, constraint_name)
  at = create_alter_table table_name
  at.validate_constraint constraint_name

  execute schema_creation.accept(at)
end

# File activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb, line 838
def validate_foreign_key(from_table, to_table = nil, **options)
  fk_name_to_validate = foreign_key_for!(from_table, to_table: to_table, **options).name

  validate_constraint from_table, fk_name_to_validate
end