R/simulate.R

In tidyverse/dbplyr: A 'dplyr' Back End for Databases

#' Simulate database connections
#'
#' These functions generate S3 objects that have been designed to simulate
#' the action of a database connection, without actually having the database
#' available. Obviously, this simulation can only be incomplete, but most
#' importantly it allows us to simulate SQL generation for any database without
#' actually connecting to it.
#'
#' Simulated SQL always quotes identifies with `` `x` ``, and strings with
#' `'x'`.
#'
#' @keywords internal
#' @export
simulate_dbi <- function(class = character(), ...) {
  structure(
    list(),
    ...,
    class = c(class, "TestConnection", "DBIConnection")
  )
}

#' @export
dbplyr_edition.TestConnection <- function(con) 2L


sql_escape_ident <- function(con, x) {
  UseMethod("sql_escape_ident")
}
#' @export
sql_escape_ident.default <- function(con, x) {
  dbQuoteIdentifier(con, x)
}
#' @export
sql_escape_ident.TestConnection <- function(con, x) {
  if (methods::is(x, "SQL")) {
    x
  } else {
    sql_quote(x, "`")
  }
}

sql_escape_string <- function(con, x) {
  UseMethod("sql_escape_string")
}
#' @export
sql_escape_string.default <- function(con, x) {
  dbQuoteString(con, x)
}
#' @export
sql_escape_string.TestConnection <- function(con, x) {
  sql_quote(x, "'")
}