SQLColumnSeed: Column of a SQL table

In Bioconductor/SQLDataFrame: Representation of SQL tables in DataFrame metaphor

Column of a SQL table

Description

Represent a column of a SQL table as a 1-dimensional DelayedArray. This allows us to use SQL data inside DataFrames without loading them into memory.

Usage

SQLColumnSeed(path, dbtype, table, column, length = NULL, type = NULL)

SQLColumnVector(x, ...)

Arguments

path	String containing a path to a SQL file.
dbtype	String containing the SQL database type (case insensitive). Supported types are "SQLite" and "DuckDB".
table	String containing the name of the table in SQL file.
column	String containing the name of the column inside the table.
length	Integer containing the number of rows. If NULL, this is determined by inspecting the SQL table. This should only be supplied for efficiency purposes, to avoid a file look-up on construction.
type	String specifying the type of the data. If NULL, this is determined by inspecting the file. Users may specify this to avoid a look-up, or to coerce the output into a different type.
x	A SQLColumnSeed object.
...	Further arguments to be passed to the SQLColumnSeed constructor. #'

Value

For SQLColumnSeed: a SQLColumnSeed. For SQLColumnVector: a SQLColumnVector. #'

Author(s)

Qian Liu

Examples

# Mocking up a file:
tf <- tempfile()
on.exit(unlink(tf))
con <- DBI::dbConnect(RSQLite::SQLite(), tf)
DBI::dbWriteTable(con, "mtcars", mtcars)
DBI::dbDisconnect(con)

# Creating a vector:
SQLColumnVector(tf, dbtype = "SQLite", "mtcars", column="gear")

# This happily lives inside DataFrames:
collected <- list()
for (x in colnames(mtcars)) {
    collected[[x]] <- SQLColumnVector(tf, dbtype = "SQLite", "mtcars", column=x)
}
DataFrame(collected)
#'

Bioconductor/SQLDataFrame documentation built on March 29, 2024, 6:41 p.m.