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Add DatabaseConnector backend #1583 #1616

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141 changes: 141 additions & 0 deletions R/backend-databaseconnector.R
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#' Backend: DatabaseConnector
#'
#' @description
#' DatabaseConnector is a DBI-compliant database backend that supports
#' multiple database systems. It uses JDBC drivers to establish connections,
#' and the connection object includes a \code{dbms} slot that specifies the
#' database type. This backend enables dplyr's SQL translations to work across
#' all database supported platforms by reusing translations
#' from other backends.
#'
#' Use `simulate_databaseconnector(dbms = "sql server")` with `lazy_frame()`
#' to see simulated SQL without connecting to live access database.
#'
#' Supported DatabaseConnector JDBC backends are:
#' \itemize{
#' \item \code{"oracle"}
#' \item \code{"postgresql"}
#' \item \code{"redshift"}
#' \item \code{"sql server"}
#' \item \code{"bigquery"}
#' \item \code{"spark"}
#' \item \code{"snowflake"}
#' \item \code{"synapse"}
#' \item \code{"iris"}
#' }
#'
#' @name backend-databaseconnector
#' @aliases NULL
#' @examples
#' library(dplyr, warn.conflicts = FALSE)
#'
#' lf <- lazy_frame(a = TRUE, b = 1, c = 2, d = "z", con = simulate_databaseconnector(dbms = "oracle"))
#' lf %>% transmute(x = paste0(c, " times"))
#' lf %>% setdiff(lf)
NULL

#' @export
#' @rdname backend-databaseconnector
simulate_databaseconnector <- function(dbms = "sql server") {
simulate_dbi("DatabaseConnectorJdbcConnection", dbms = dbms)
}

#' @export
#' @importFrom dbplyr dbplyr_edition
#'
#' @param con Database connection
dbplyr_edition.DatabaseConnectorConnection <- function(con) {
2L
}

#' @export
sql_query_select.DatabaseConnectorJdbcConnection <- function(con,
select,
from,
where = NULL,
group_by = NULL,
having = NULL,
window = NULL,
order_by = NULL,
limit = NULL,
distinct = FALSE,
...,
subquery = FALSE,
lvl = 0) {

if (isS4(con)) {
dbms <- con@dbms
} else {
# for testing with simulated connections
dbms <- attr(con, "dbms")
}

switch(dbms,
"sql server" = `sql_query_select.Microsoft SQL Server`(con,
select,
from,
where,
group_by,
having,
window,
order_by,
limit,
distinct,
...,
subquery,
lvl),
"oracle" = sql_query_select.Oracle(con,
select,
from,
where,
group_by,
having,
window,
order_by,
limit,
distinct,
...,
subquery,
lvl),
NextMethod()
)
}

#' @export
sql_translation.DatabaseConnectorJdbcConnection <- function(con) {

if (isS4(con)) {
dbms <- con@dbms
} else {
dbms <- attr(con, "dbms")
}

switch(dbms,
"oracle" = sql_translation.Oracle(con),
"postgresql" = sql_translation.PqConnection(con),
"redshift" = sql_translation.RedshiftConnection(con),
"sql server" = `sql_translation.Microsoft SQL Server`(con),
"bigquery" = sql_translation.BigQueryConnection(con),
"spark" = `sql_translation.Spark SQL`(con),
"snowflake" = sql_translation.Snowflake(con),
"synapse" = `sql_translation.Microsoft SQL Server`(con),
"iris" = sql_translation.PqConnection(con),
rlang::abort("Sql dialect is not supported!"))
}

#' @export
sql_escape_logical.DatabaseConnectorJdbcConnection <- function(con, x) {

if (isS4(con)) {
dbms <- con@dbms
} else {
dbms <- attr(con, "dbms")
}

if (dbms == "sql server") {
dplyr::if_else(x, "1", "0", missing = "NULL")
} else {
NextMethod()
}
}

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