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Use dbWriteTable Copy in dbAppendTable to Eliminate Slowdown #286

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Use dbWriteTable Copy in dbAppendTable to Eliminate Slowdown #286

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c21ac19
replace dbAppendTable code with code from dbWriteTable when append = …
JSchoenbachler Jan 18, 2021
b8c68c8
Return amount of rows affected
JSchoenbachler Jan 22, 2021
94ac2b7
Add warning if factor.
JSchoenbachler Jan 22, 2021
0d8e2d1
Apply suggestions from code review
JSchoenbachler Jan 22, 2021
07e0813
Apply suggestions from code review
JSchoenbachler Jan 22, 2021
52bf977
Update with feedback from pull request
JSchoenbachler Jan 25, 2021
f3490ac
Add param for 'warn' and run 'devtools::document()'
JSchoenbachler Jan 26, 2021
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53 changes: 26 additions & 27 deletions R/tables.R
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Original file line number Diff line number Diff line change
Expand Up @@ -24,6 +24,7 @@
#' and uses `COPY name FROM stdin`. This is fast, but not supported by
#' all postgres servers (e.g. Amazon's redshift). If `FALSE`, generates
#' a single SQL string. This is slower, but always supported.
#' @param warn If `TRUE`, warns user when converting from factor to string.
#'
#' @examples
#' # For running the examples on systems without PostgreSQL connection:
Expand Down Expand Up @@ -108,22 +109,7 @@ setMethod("dbWriteTable", c("PqConnection", "character", "data.frame"),
}

if (nrow(value) > 0) {
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if (!copy) {
value <- sqlData(conn, value, row.names = FALSE)

sql <- sqlAppendTable(conn, name, value, row.names = FALSE)
dbExecute(conn, sql)
} else {
value <- sql_data_copy(value, row.names = FALSE)

fields <- dbQuoteIdentifier(conn, names(value))
sql <- paste0(
"COPY ", dbQuoteIdentifier(conn, name),
" (", paste(fields, collapse = ", "), ")",
" FROM STDIN"
)
connection_copy_data(conn@ptr, sql, value)
}
dbAppendTable(conn, name, value, copy, warn = FALSE)
}

invisible(TRUE)
Expand Down Expand Up @@ -188,20 +174,33 @@ format_keep_na <- function(x, ...) {
#' @rdname postgres-tables
#' @export
setMethod("dbAppendTable", c("PqConnection"),
function(conn, name, value, ..., row.names = NULL) {
function(conn, name, value, copy = TRUE, warn = TRUE, ..., row.names = NULL) {
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We don't need a warn argument here, dbAppendTable() is a new generic.

Suggested change
function(conn, name, value, copy = TRUE, warn = TRUE, ..., row.names = NULL) {
function(conn, name, value, ..., copy = TRUE, row.names = NULL) {

stopifnot(is.null(row.names))

query <- sqlAppendTableTemplate(
con = conn,
table = name,
values = value,
row.names = row.names,
prefix = "$",
pattern = "1",
...
)
row.names <- FALSE

value = factor_to_string(value, warn = warn)
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Suggested change
value = factor_to_string(value, warn = warn)
value = factor_to_string(value, warn = TRUE)


value <- sqlRownamesToColumn(value, row.names)

if (!copy) {
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What happens here if the input has zero rows? Do we have a test for this in DBItest?

value <- sqlData(conn, value, row.names = FALSE)

sql <- sqlAppendTable(conn, name, value, row.names = FALSE)
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I wonder if the previous approach via sqlAppendTableTemplate() works with Redshift? Can we implement a dbAppendTable() method for a RedshiftConnection that uses sqlAppendTable() and keep using sqlAppendTableTemplate() in the PqConnection method?

dbExecute(conn, sql)
} else {
value <- sql_data_copy(value, row.names = FALSE)

fields <- dbQuoteIdentifier(conn, names(value))
sql <- paste0(
"COPY ", dbQuoteIdentifier(conn, name),
" (", paste(fields, collapse = ", "), ")",
" FROM STDIN"
)
connection_copy_data(conn@ptr, sql, value)
}

dbExecute(conn, query, params = unname(as.list(value)))
nrow(value)
}
)

Expand Down
12 changes: 11 additions & 1 deletion man/postgres-tables.Rd
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