Parameterized rquery
In rquery: Relational Query Generator for Data Manipulation at Scale

rquery 1.2.0 now incorporates bquote() quasi-quotation.

In fact this is enough to allow rqdatatable to directly work the indirect column names example from our bquote() articles (1, 2).

First let's check what packages we have available for these examples.

have_rqdatatable <- FALSE
if (requireNamespace("rqdatatable", quietly = TRUE)) {
  library("rqdatatable")
  have_rqdatatable <- TRUE
}
have_db <- FALSE
if (requireNamespace("RSQLite", quietly = TRUE) &&
    requireNamespace("DBI", quietly = TRUE)) {
  have_db <- TRUE
}

library("rquery")

# define our parameters
# pretend these come from far away
# or as function arguments.
group_nm <- "am"
num_nm <- as.name("hp")
den_nm <- as.name("cyl")
derived_nm <- as.name(paste0(num_nm, "_per_", den_nm))
mean_nm <- as.name(paste0("mean_", derived_nm))
count_nm <- as.name("group_count")

Immediate mode example (note we are using newer rquery 1.2.1 notation "extend()" instead of extend_nse()).

# apply a parameterized pipeline using bquote
mtcars %.>%
  extend(., 
         .(derived_nm) := .(num_nm)/.(den_nm)) %.>%
  project(., 
          .(mean_nm) := mean(.(derived_nm)),
          .(count_nm) := length(.(derived_nm)),
          groupby = group_nm) %.>%
  orderby(., 
          group_nm)

Stored operator tree examples.

# make an abstract description of the table to start with
td <- mk_td("mtcars",
            as.character(list(group_nm, num_nm, den_nm)))

# helper function to adapt to later database environemnt
count <- function(v) { length(v) }

# capture the operator pipeline
ops <- td %.>%
  extend(., 
         .(derived_nm) := .(num_nm)/.(den_nm)) %.>%
  project(., 
          .(mean_nm) := mean(.(derived_nm)),
          .(count_nm) := count(.(derived_nm)),
          groupby = group_nm) %.>%
  orderby(., 
          group_nm)

# apply it to data
mtcars %.>% ops

We can display the pipeline in various forms.

# print the operator sequence
cat(format(ops))

The same example in a database.

# connect to a database
raw_connection <- DBI::dbConnect(RSQLite::SQLite(), ":memory:")

# build a representation of the database connection
dbopts <- rq_connection_tests(raw_connection)
db <- rquery_db_info(connection = raw_connection,
                     is_dbi = TRUE,
                     connection_options = dbopts)
print(db)

# copy data to db
tr <- rquery::rq_copy_to(db, "mtcars", mtcars, 
                         temporary = TRUE, 
                         overwrite = TRUE)
print(tr)

# materialize result remotely (without passing through R)
res <- materialize(db, ops)
DBI::dbReadTable(raw_connection, res$table_name)

# or execute and pull results back
execute(db, ops)

# print the derived sql
sql <- to_sql(ops, db)
cat(sql)

# disconnect
DBI::dbDisconnect(raw_connection)
rm(list = c("raw_connection", "db"))