Format log events for output to databases

LayoutDbi can contain col_types that AppenderDbi can use to create new database tables; however, it is safer and more flexible to set up the log table up manually with an SQL CREATE TABLE statement instead.

Value

The $new() method returns an R6::R6 that inherits from lgr::Layout and can used as a Layout by an lgr::Appender.

Details

The LayoutDbi parameters fmt, timestamp_fmt, colors and pad_levels are only applied for for console output via the $show() method and do not influence database inserts in any way. The inserts are pre-processed by the methods $format_data(), $format_colnames and $format_tablenames.

It does not format LogEvents directly, but their data.table representations (see as.data.table.LogEvent), as well as column- and table names.

Database Specific Layouts

Different databases have different data types and features. Currently the following LayoutDbi subclasses exist that deal with specific databases, but this list is expected to grow as lgrExtra matures:

  • LayoutSqlite: For SQLite databases

  • LayoutPostgres: for Postgres databases

  • LayoutMySql: for MySQL databases

  • LayoutDb2: for DB2 databases

The utility function select_dbi_layout() tries returns the appropriate Layout for a DBI connection, but this does not work for odbc and JDBC connections where you have to specify the layout manually.

For creating custom DB-specific layouts it should usually be enough to create an R6::R6 class that inherits from LayoutDbi and choosing different defaults for $format_table_name, $format_colnames and $format_data.

Super classes

lgr::Layout -> lgr::LayoutFormat -> LayoutDbi

Public fields

format_table_name

a function to format the table name before inserting to the database. The function will be applied to the $table_name before inserting into the database. For example some, databases prefer all lowercase names, some uppercase. SQL updates should be case-agnostic, but sadly in practice not all DBI backends behave consistently in this regard.

format_colnames

a function to format the column names before inserting to the database. The function will be applied to the column names of the data frame to be inserted into the database.

format_data

a function to format the data before inserting into the database. The function will be applied to the whole data frame.

names

of the columns that contain data that has been serialized to JSON strings

Active bindings

col_types

a named character vector of column types supported by the target database. If not NULL this is used by AppenderDbi or similar Appenders to create a new database table on instantiation of the Appender. If the target database table already exists, col_types is not used.

names

of the columns that contain data that has been serialized to JSON strings

col_names

column names of the target table (the same as names(lo$col_types))

Methods

Public methods

Inherited methods

Method new()

Usage

LayoutDbi$new(
  col_types = c(level = "integer", timestamp = "timestamp", logger = "varchar(256)",
    caller = "varchar(256)", msg = "varchar(2048)"),
  serialized_cols = NULL,
  fmt = "%L [%t] %m  %f",
  timestamp_fmt = "%Y-%m-%d %H:%M:%S",
  colors = getOption("lgr.colors", list()),
  pad_levels = "right",
  format_table_name = identity,
  format_colnames = identity,
  format_data = data.table::as.data.table
)

Method set_col_types()

Usage

LayoutDbi$set_col_types(x)

Method set_serialized_cols()

Usage

LayoutDbi$set_serialized_cols(x)

Method sql_create_table()

Usage

LayoutDbi$sql_create_table(table)

Method toString()

Usage

LayoutDbi$toString()

Method clone()

The objects of this class are cloneable with this method.

Usage

LayoutDbi$clone(deep = FALSE)

Arguments

deep

Whether to make a deep clone.