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#' Copy a local data frame to a remote database
#'
#' @description
#' This is an implementation of the dplyr [copy_to()] generic and it mostly
#' a wrapper around [DBI::dbWriteTable()].
#'
#' It is useful for copying small amounts of data to a database for examples,
#' experiments, and joins. By default, it creates temporary tables which are
#' only visible within the current connection to the database.
#'
#' @export
#' @param df A local data frame, a `tbl_sql` from same source, or a `tbl_sql`
#' from another source. If from another source, all data must transition
#' through R in one pass, so it is only suitable for transferring small
#' amounts of data.
#' @param name Name of new remote table. Use a string to create the table
#' in the current catalog/schema. Use `I()` if you want to create it
#' in a specific catalog/schema, e.g. `I("schema.table")`.
#' @param types a character vector giving variable types to use for the columns.
#' See <https://www.sqlite.org/datatype3.html> for available types.
#' @param temporary if `TRUE`, will create a temporary table that is
#' local to this connection and will be automatically deleted when the
#' connection expires
#' @param unique_indexes a list of character vectors. Each element of the list
#' will create a new unique index over the specified column(s). Duplicate rows
#' will result in failure.
#' @param indexes a list of character vectors. Each element of the list
#' will create a new index.
#' @param analyze if `TRUE` (the default), will automatically ANALYZE the
#' new table so that the query optimiser has useful information.
#' @param in_transaction Should the table creation be wrapped in a transaction?
#' This typically makes things faster, but you may want to suppress if the
#' database doesn't support transactions, or you're wrapping in a transaction
#' higher up (and your database doesn't support nested transactions.)
#' @inheritParams dplyr::copy_to
#' @inherit arrange.tbl_lazy return
#' @seealso [copy_inline()] to use small data in an SQL query without actually
#' writing to a table.
#' @examples
#' library(dplyr, warn.conflicts = FALSE)
#'
#' df <- data.frame(x = 1:5, y = letters[5:1])
#' db <- copy_to(src_memdb(), df)
#' db
#'
#' df2 <- data.frame(y = c("a", "d"), fruit = c("apple", "date"))
#' # copy_to() is called automatically if you set copy = TRUE
#' # in the join functions
#' db %>% left_join(df2, copy = TRUE)
#' @importFrom dplyr copy_to
copy_to.src_sql <- function(dest,
df,
name = deparse(substitute(df)),
overwrite = FALSE,
types = NULL,
temporary = TRUE,
unique_indexes = NULL,
indexes = NULL,
analyze = TRUE,
...,
in_transaction = TRUE) {
check_bool(temporary)
if (!is.data.frame(df) && !inherits(df, "tbl_sql")) {
cli_abort("{.var df} must be a local dataframe or a remote tbl_sql")
}
name <- as_table_path(name, dest$con)
if (inherits(df, "tbl_sql") && same_src(df$src, dest)) {
out <- compute(df,
name = name,
temporary = temporary,
unique_indexes = unique_indexes,
indexes = indexes,
analyze = analyze,
...
)
} else {
# avoid S4 dispatch problem in dbSendPreparedQuery
df <- as.data.frame(collect(df))
name <- db_copy_to(dest$con, name, df,
overwrite = overwrite,
types = types,
temporary = temporary,
unique_indexes = unique_indexes,
indexes = indexes,
analyze = analyze,
in_transaction = in_transaction,
...
)
out <- tbl_src_dbi(dest, name, vars = names(df))
}
invisible(out)
}
#' @importFrom dplyr auto_copy
#' @export
auto_copy.tbl_sql <- function(x, y, copy = FALSE, ...) {
copy_to(x$src, as.data.frame(y), unique_table_name(), ...)
}
#' Use a local data frame in a dbplyr query
#'
#' This is an alternative to [copy_to()] that does not need write access and
#' is faster for small data.
#'
#' It writes the data directly in the SQL query via the `VALUES` clause.
#'
#' @seealso [copy_to()] to copy the data into a new database table.
#' @export
#' @param con A database connection.
#' @param df A local data frame. The data is written directly in the SQL query
#' so it should be small.
#' @param types A named character vector of SQL data types to use for the columns.
#' The data types are backend specific. For example for Postgres this could
#' be `c(id = "bigint", created_at = "timestamp", values = "integer[]")`.
#' If `NULL`, the default, the types are determined from `df`.
#' @return A `tbl_lazy`.
#'
#' @examples
#' df <- data.frame(x = 1:3, y = c("a", "b", "c"))
#' con <- DBI::dbConnect(RSQLite::SQLite(), ":memory:")
#'
#' copy_inline(con, df)
#'
#' copy_inline(con, df) %>% dplyr::show_query()
copy_inline <- function(con, df, types = NULL) {
if (!inherits(df, "data.frame")) {
cli_abort("{.var df} needs to be a data.frame.")
}
if (ncol(df) == 0) {
cli_abort("{.var df} needs at least one column.")
}
if (!is_null(types)) {
check_character(types)
if (!setequal(colnames(df), names(types))) {
cli_abort("Names of {.arg df} and {.arg types} must be the same.")
}
}
# This workaround is needed because `tbl_sql()` applies `as.sql()` on `from`
subclass <- class(con)[[1]] # prefix added by dplyr::make_tbl
dplyr::make_tbl(
c(subclass, "sql", "lazy"),
src = src_dbi(con),
from = df,
lazy_query = lazy_values_query(df, types),
vars = colnames(df)
)
}
lazy_values_query <- function(df, types) {
lazy_query(
query_type = "values",
x = df,
col_types = types,
group_vars = character(),
order_vars = NULL,
frame = NULL
)
}
#' @export
sql_build.lazy_values_query <- function(op, con, ..., sql_options = NULL) {
class(op) <- c("values_query", "query")
op
}
#' @export
sql_render.values_query <- function(query,
con = query$src$con,
...,
sql_options = NULL,
subquery = FALSE,
lvl = 0) {
sql_values_subquery(con, query$x, types = query$col_types, lvl = lvl)
}
#' @export
flatten_query.values_query <- function(qry, query_list, con) {
querylist_reuse_query(qry, query_list, con)
}
#' @export
op_vars.lazy_values_query <- function(op) {
colnames(op$x)
}
sql_values_subquery <- function(con, df, types, lvl = 0, ...) {
check_dots_used()
UseMethod("sql_values_subquery")
}
#' @export
sql_values_subquery.DBIConnection <- function(con, df, types, lvl = 0, ...) {
sql_values_subquery_default(con, df, types = types, lvl = lvl, row = FALSE)
}
sql_values_subquery_default <- function(con, df, types, lvl, row) {
df <- values_prepare(con, df)
if (nrow(df) == 0L) {
return(sql_values_zero_rows(con, df, types, lvl))
}
# The query consists of two parts:
# 1) An outer select which converts the values to the correct types. This needs
# to use the translation of `as.<column type>(<column name>)` (e.g. `as.numeric(mpg)`)
# because some backends need a special translation for some types e.g. casting
# to logical/bool in MySQL
# `IF(<column name>, TRUE, FALSE)`
# This is done with the help of `sql_cast_dispatch()` via dispatch on the
# column type. The explicit cast is required so that joins work e.g. on date
# columns in Postgres.
# 2) A subquery which is the union of:
# a) a zero row table which is just required to name the columns. This is
# necessary as e.g. SQLite cannot name `VALUES`.
# b) `VALUES` clause
sim_data <- rep_named(colnames(df), list(NULL))
cols_clause <- escape(sim_data, con = con, parens = FALSE, collapse = NULL)
null_row_clauses <- list(
select = sql_clause_select(con, cols_clause),
where = sql_clause_where(sql("0 = 1"))
)
rows_clauses <- sql_values_clause(con, df, row = row)
rows_query <- sql_format_clauses(rows_clauses, lvl = lvl + 1, con = con)
subquery <- sql_query_union(
con,
x = sql_format_clauses(null_row_clauses, lvl + 1, con),
unions = list(table = as.character(rows_query), all = TRUE),
lvl = lvl + 1
)
sql_query_select(
con,
select = sql_values_cast_clauses(con, df, types, na = FALSE),
from = sql_query_wrap(con, subquery, name = "values_table", lvl = lvl),
lvl = lvl
)
}
sql_values_subquery_column_alias <- function(con, df, types, lvl, ...) {
df <- values_prepare(con, df)
if (nrow(df) == 0L) {
return(sql_values_zero_rows(con, df, types, lvl))
}
# The `SELECT` clause converts the values to the correct types. This needs
# to use the translation of `as.<column type>(<column name>)` (e.g. `as.numeric(mpg)`)
# because some backends need a special translation for some types e.g. casting
# to logical/bool in MySQL
# `IF(<column name>, TRUE, FALSE)`
# This is done with the help of `sql_cast_dispatch()` via dispatch on the
# column type. The explicit cast is required so that joins work e.g. on date
# columns in Postgres.
# The `FROM` clause is simply the `VALUES` clause with table and column alias
rows_clauses <- sql_values_clause(con, df, row = FALSE)
rows_query <- sql_format_clauses(rows_clauses, lvl = lvl + 1, con = con)
table_alias_sql <- sql(paste0("drvd(", escape(ident(colnames(df)), con = con), ")"))
if (grepl("\\n", rows_query)) {
rows_query <- sql(paste0("(\n", rows_query, "\n", indent_lvl(") AS ", lvl), table_alias_sql))
} else {
# indent is not perfect but okay
rows_query <- sql(paste0("(", rows_query, ") AS ", table_alias_sql))
}
sql_query_select(
con,
select = sql_values_cast_clauses(con, df, types, na = FALSE),
from = rows_query,
lvl = lvl
)
}
sql_values_subquery_union <- function(con, df, types, lvl, row, from = NULL) {
df <- values_prepare(con, df)
if (nrow(df) == 0L) {
return(sql_values_zero_rows(con, df, types, lvl, from))
}
# The query consists of two parts:
# 1) An outer select which converts the values to the correct types. This needs
# to use the translation of `as.<column type>(<column name>)` (e.g. `as.numeric(mpg)`)
# because some backends need a special translation for some types e.g. casting
# to logical/bool in MySQL
# `IF(<column name>, TRUE, FALSE)`
# This is done with the help of `sql_cast_dispatch()` via dispatch on the
# column type. The explicit cast is required so that joins work e.g. on date
# columns in Postgres.
# 2) A subquery which is the union of:
# a) a zero row table which is just required to name the columns. This is
# necessary as e.g. SQLite cannot name `VALUES`.
# b) `UNION ALL` of one row `SELECT` statements
sim_data <- rep_named(colnames(df), list(NULL))
cols_clause <- escape(sim_data, con = con, parens = FALSE, collapse = NULL)
clauses <- list(
select = sql_clause_select(con, cols_clause),
from = if (!is.null(from)) sql_clause_from(ident(from)),
where = sql_clause_where(sql("0 = 1"))
)
null_row_query <- sql_format_clauses(clauses, lvl + 1, con)
escaped_values <- purrr::map(df, escape, con = con, collapse = NULL, parens = FALSE)
rows <- rlang::exec(paste, !!!escaped_values, sep = ", ")
select_kw <- style_kw("SELECT ")
tables <- paste0(lvl_indent(lvl + 1), select_kw, rows)
if (!is_null(from)) {
from_kw <- style_kw("FROM ")
tables <- paste0(tables, " ", from_kw, from)
}
subquery <- sql_query_union(
con,
x = null_row_query,
unions = list(all = TRUE, table = tables),
lvl = lvl + 1
)
sql_query_select(
con,
select = sql_values_cast_clauses(con, df, types, na = FALSE),
from = sql_query_wrap(con, subquery, name = "values_table", lvl = lvl),
lvl = lvl
)
}
sql_values_clause <- function(con, df, row = FALSE) {
escaped_values <- purrr::map(df, escape, con = con, collapse = NULL, parens = FALSE)
rows <- rlang::exec(paste, !!!escaped_values, sep = ", ")
rows_sql <- sql(paste0(if (row) "ROW", "(", rows, ")"))
list(sql_clause("VALUES", rows_sql))
}
sql_values_zero_rows <- function(con, df, types, lvl, from = NULL) {
if (nrow(df) != 0L) {
cli_abort("{.arg df} does not have 0 rows", .internal = TRUE)
}
typed_cols <- sql_values_cast_clauses(con, df, types, na = TRUE)
clauses <- list(
select = sql_clause_select(con, typed_cols),
from = if (!is.null(from)) sql_clause_from(ident(from)),
where = sql_clause_where(sql("0 = 1"))
)
sql_format_clauses(clauses, lvl, con)
}
sql_values_cast_clauses <- function(con, df, types, na) {
if (is_null(types)) {
typed_cols <- purrr::map2_chr(
df, colnames(df),
~ {
val <- if (na) NA else ident(.y)
cast_expr <- call2(sql_cast_dispatch(.x), val)
translate_sql(!!cast_expr, con = con)
}
)
} else {
typed_cols <- purrr::imap_chr(
types,
~ {
val <- if (na) NA else ident(.y)
sql_expr(cast(!!val %as% !!sql(.x)), con = con)
}
)
}
sql_vector(typed_cols, parens = FALSE, collapse = NULL, con = con)
}
values_prepare <- function(con, df) {
UseMethod("values_prepare")
}
#' @export
values_prepare.DBIConnection <- function(con, df) {
df
}
# This
sql_cast_dispatch <- function(x) {
UseMethod("sql_cast_dispatch")
}
#' @export
sql_cast_dispatch.sql <- function(x) {
expr(as.character)
}
#' @export
sql_cast_dispatch.logical <- function(x) {
expr(as.logical)
}
#' @export
sql_cast_dispatch.integer <- function(x) {
expr(as.integer)
}
#' @export
sql_cast_dispatch.numeric <- function(x) {
expr(as.numeric)
}
#' @export
sql_cast_dispatch.character <- function(x) {
expr(as.character)
}
#' @export
sql_cast_dispatch.factor <- function(x) {
expr(as.character)
}
#' @export
sql_cast_dispatch.Date <- function(x) {
expr(as.Date)
}
#' @export
sql_cast_dispatch.POSIXct <- function(x) {
expr(as.POSIXct)
}
#' @export
sql_cast_dispatch.integer64 <- function(x) {
expr(as.integer64)
}
utils::globalVariables(c("as.integer64"))
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