SQL_extensions: SQL extensions

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

SQL extensions

Description

Extensions of SQLDataFrame, SQLColumnVector, SQLColumnSeed with different SQL backends. Currently supporting SQLite and DuckDB, with which the definition coding can be followed for added extension of other SQL backends.

Arguments

path	String containing a path to a SQL file.
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.

Examples

## Mocking up a file:

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

### DuckDB
tf1 <- tempfile()
on.exit(unlist(tf1))
con <- DBI::dbConnect(duckdb::duckdb(), tf1)
DBI::dbWriteTable(con, "mtcars", mtcars)
DBI::dbDisconnect(con)

## Constructor of xxColumnSeed and xxColumnVector

sd <- SQLiteColumnSeed(tf, "mtcars", "gear")
scv <- SQLiteColumnVector(sd)
scv1 <- SQLiteColumnVector(tf, "mtcars", "gear")
identical(scv, scv1)

DuckDBColumnSeed(tf1, "mtcars", "mpg")
DuckDBColumnVector(tf1, "mtcars", "mpg")

## Constructor of xxDataFrame

SQLiteDataFrame(tf, "mtcars")
DuckDBDataFrame(tf1, "mtcars")

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