A 'dplyr' Back End for Databases

A 'dplyr' back end for databases that allows you to work with remote database tables as if they are in-memory data frames. Basic features works with any database that has a 'DBI' back end; more advanced features require 'SQL' translation to be provided by the package author.


Build Status CRAN_Status_Badge Coverage Status

Overview

dbplyr is the database backend for dplyr. If you are using dplyr to connect to databases, you generally will not need to use any functions from dbplyr, but you will need to make sure it's installed.

Issues

If you find any bugs, please file in dplyr.

Installation

install.packages("dbplyr")
 
# Or the the development version from GitHub:
# install.packages("devtools")
devtools::install_github("tidyverse/dbplyr")

Usage

library(dplyr, warn.conflicts = FALSE)
 
con <- DBI::dbConnect(RSQLite::SQLite(), ":memory:")
copy_to(con, mtcars)
 
mtcars2 <- tbl(con, "mtcars")
mtcars2
#> # Source:   table<mtcars> [?? x 11]
#> # Database: sqlite 3.19.3 [:memory:]
#>      mpg   cyl  disp    hp  drat    wt  qsec    vs    am  gear  carb
#>    <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl>
#>  1  21.0     6 160.0   110  3.90 2.620 16.46     0     1     4     4
#>  2  21.0     6 160.0   110  3.90 2.875 17.02     0     1     4     4
#>  3  22.8     4 108.0    93  3.85 2.320 18.61     1     1     4     1
#>  4  21.4     6 258.0   110  3.08 3.215 19.44     1     0     3     1
#>  5  18.7     8 360.0   175  3.15 3.440 17.02     0     0     3     2
#>  6  18.1     6 225.0   105  2.76 3.460 20.22     1     0     3     1
#>  7  14.3     8 360.0   245  3.21 3.570 15.84     0     0     3     4
#>  8  24.4     4 146.7    62  3.69 3.190 20.00     1     0     4     2
#>  9  22.8     4 140.8    95  3.92 3.150 22.90     1     0     4     2
#> 10  19.2     6 167.6   123  3.92 3.440 18.30     1     0     4     4
#> # ... with more rows

News

dbplyr 1.2.2

  • R CMD check fixes

dbplyr 1.2.1

  • Forward compatibility fixes for rlang 0.2.0

dbplyr 1.2.0

New top-level translations

  • New translations for

    • MS Access (#2946) (@DavisVaughan)
    • Oracle, via odbc or ROracle (#2928, #2732, @edgararuiz)
    • Teradata.
    • Redshift.
  • dbplyr now supplies appropriate translations for the RMariaDB and RPostgres packages (#3154). We generally recommend using these packages in favour of the older RMySQL and RPostgreSQL packages as they are fully DBI compliant and tested with DBItest.

New features

  • copy_to() can now "copy" tbl_sql in the same src, providing another way to cache a query into a temporary table (#3064). You can also copy_to tbl_sqls from another source, and copy_to() will automatically collect then copy.

  • Initial support for stringr functions: str_length(), str_to_upper(), str_to_lower(), str_replace_all(), str_detect(), str_trim(). Regular expression support varies from database to database, but most simple regular expressions should be ok.

Tools for developers

  • db_compute() gains an analyze argument to match db_copy_to().

  • New remote_name(), remote_con(), remote_src(), remote_query() and remote_query_plan() provide a standard API for get metadata about a remote tbl (#3130, #2923, #2824).

  • New sql_expr() is a more convenient building block for low-level SQL translation (#3169).

  • New sql_aggregate() and win_aggregate() for generating SQL and windowed SQL functions for aggregates. These take one argument, x, and warn if na.rm is not TRUE (#3155). win_recycled() is equivalent to win_aggregate() and has been soft-deprecated.

  • db_write_table now needs to return the table name

Minor improvements and bug fixes

  • Multiple head() calls in a row now collapse to a single call. This avoids a printing problem with MS SQL (#3084).

  • escape() now works with integer64 values from the bit64 package (#3230)

  • if, ifelse(), and if_else() now correctly scope the false condition so that it only applies to non-NULL conditions (#3157)

  • ident() and ident_q() handle 0-length inputs better, and should be easier to use with S3 (#3212)

  • in_schema() should now work in more places, particularly in copy_to() (#3013, @baileych)

  • SQL generation for joins no longer gets stuck in a endless loop if you request an empty suffix (#3220).

  • mutate() has better logic for splitting a single mutate into multiple subqueries (#3095).

  • Improved paste() and paste0() support in MySQL, PostgreSQL (#3168), and RSQLite (#3176). MySQL and PostgreSQL gain support for str_flatten() which behaves like paste(x, collapse = "-") (but for technical reasons can't be implemented as a straightforward translation of paste()).

  • same_src.tbl_sql() now performs correct comparison instead of always returning TRUE. This means that copy = TRUE once again allows you to perform cross-database joins (#3002).

  • select() queries no longer alias column names unnecessarily (#2968, @DavisVaughan).

  • select() and rename() are now powered by tidyselect, fixing a few renaming bugs (#3132, #2943, #2860).

  • summarise() once again performs partial evaluation before database submission (#3148).

  • test_src() makes it easier to access a single test source.

Database specific improvements

  • MS SQL

    • Better support for temporary tables (@Hong-Revo)

    • Different translations for filter/mutate contexts for: NULL evaluation (is.na(), is.null()), logical operators (!, &, &&, |, ||), and comparison operators (==, !=, <, >, >=, <=)

  • MySQL: copy_to() (via db_write_table()) correctly translates logical variables to integers (#3151).

  • odbc: improved n() translation in windowed context.

  • SQLite: improved na_if translation (@cwarden)

  • PostgreSQL: translation for grepl() added (@zozlak)

dbplyr 1.1.0

New features

  • full_join() over non-overlapping columns by = character() translated to CROSS JOIN (#2924).

  • case_when() now translates to SQL "CASE WHEN" (#2894)

  • x %in% c(1) now generates the same SQL as x %in% 1 (#2898).

  • New window_order() and window_frame() give you finer control over the window functions that dplyr creates (#2874, #2593).

  • Added SQL translations for Oracle (@edgararuiz).

Minor improvements and bug fixes

  • x %in% c(1) now generates the same SQL as x %in% 1 (#2898).

  • head(tbl, 0) is now supported (#2863).

  • select()ing zero columns gives a more information error message (#2863).

  • Variables created in a join are now disambiguated against other variables in the same table, not just variables in the other table (#2823).

  • PostgreSQL gains a better translation for round() (#60).

  • Added custom db_analyze_table() for MS SQL, Oracle, Hive and Impala (@edgararuiz)

  • Added support for sd() for aggregate and window functions (#2887) (@edgararuiz)

  • You can now use the magrittr pipe within expressions, e.g. mutate(mtcars, cyl %>% as.character()).

  • If a translation was supplied for a summarise function, but not for the equivalent windowed variant, the expression would be translated to NULL with a warning. Now sql_variant() checks that all aggregate functions have matching window functions so that correct translations or clean errors will be generated (#2887)

dbplyr 1.0.0

New features

  • tbl() and copy_to() now work directly with DBI connections (#2423, #2576), so there is no longer a need to generate a dplyr src.

    library(dplyr)
     
    con <- DBI::dbConnect(RSQLite::SQLite(), ":memory:")
    copy_to(con, mtcars)
     
    mtcars2 <- tbl(con, "mtcars")
    mtcars2
  • glimpse() now works with remote tables (#2665)

  • dplyr has gained a basic SQL optimiser, which collapses certain nested SELECT queries into a single query (#1979). This will improve query execution performance for databases with less sophisticated query optimisers, and fixes certain problems with ordering and limits in subqueries (#1979). A big thanks goes to @hhoeflin for figuring out this optimisation.

  • compute() and collapse() now preserve the "ordering" of rows. This only affects the computation of window functions, as the rest of SQL does not care about row order (#2281).

  • copy_to() gains an overwrite argument which allows you to overwrite an existing table. Use with care! (#2296)

  • New in_schema() function makes it easy to refer to tables in schema: in_schema("my_schema_name", "my_table_name").

Deprecated and defunct

  • query() is no longer exported. It hasn't been useful for a while so this shouldn't break any code.

Verb-level SQL generation

  • Partial evaluation occurs immediately when you execute a verb (like filter() or mutate()) rather than happening when the query is executed (#2370).

  • mutate.tbl_sql() will now generate as many subqueries as necessary so that you can refer to variables that you just created (like in mutate with regular dataframes) (#2481, #2483).

  • SQL joins have been improved:

    • SQL joins always use the ON ... syntax, avoiding USING ... even for natural joins. Improved handling of tables with columns of the same name (#1997, @javierluraschi). They now generate SQL more similar to what you'd write by hand, eliminating a layer or two of subqueries (#2333)

    • [API] They now follow the same rules for including duplicated key variables that the data frame methods do, namely that key variables are only kept from x, and never from y (#2410)

    • [API] The sql_join() generic now gains a vars argument which lists the variables taken from the left and right sides of the join. If you have a custom sql_join() method, you'll need to update how your code generates joins, following the template in sql_join.generic().

    • full_join() throws a clear error when you attempt to use it with a MySQL backend (#2045)

    • right_join() and full_join() now return results consistent with local data frame sources when there are records in the right table with no match in the left table. right_join() returns values of by columns from the right table. full_join() returns coalesced values of by columns from the left and right tables (#2578, @ianmcook)

  • group_by() can now perform an inline mutate for database backends (#2422).

  • The SQL generation set operations (intersect(), setdiff(), union(), and union_all()) have been considerably improved.

    By default, the component SELECT are surrounded with parentheses, except on SQLite. The SQLite backend will now throw an error if you attempt a set operation on a query that contains a LIMIT, as that is not supported in SQLite (#2270).

    All set operations match column names across inputs, filling in non-matching variables with NULL (#2556).

  • rename() and group_by() now combine correctly (#1962)

  • tbl_lazy() and lazy_tbl() have been exported. These help you test generated SQL with out an active database connection.

  • ungroup() correctly resets grouping variables (#2704).

Vector-level SQL generation

  • New as.sql() safely coerces an input to SQL.

  • More tranlators for as.character(), as.integer() and as.double() (#2775).

  • New ident_q() makes it possible to specifier identifiers that do not need to be quoted.

  • Translation of inline scalars:

    • Logical values are now translated differently depending on the backend. The default is to use "true" and "false" which is the SQL-99 standard, but not widely support. SQLite translates to "0" and "1" (#2052).

    • Inf and -Inf are correctly escaped

    • Better test for whether or not a double is similar to an integer and hence needs a trailing 0.0 added (#2004).

    • Quoting defaults to DBI::dbEscapeString() and DBI::dbQuoteIdentifier() respectively.

  • :: and ::: are handled correctly (#2321)

  • x %in% 1 is now correctly translated to x IN (1) (#511).

  • ifelse() and if_else() use correct argument names in SQL translation (#2225).

  • ident() now returns an object with class c("ident", "character"). It no longer contains "sql" to indicate that this is not already escaped.

  • is.na() and is.null() gain extra parens in SQL translation to preserve correct precedence (#2302).

  • [API] log(x, b) is now correctly translated to the SQL log(b, x) (#2288). SQLite does not support the 2-argument log function so it is translated to log(x) / log(b).

  • nth(x, i) is now correctly translated to nth_value(x, i).

  • n_distinct() now accepts multiple variables (#2148).

  • [API] substr() is now translated to SQL, correcting for the difference in the third argument. In R, it's the position of the last character, in SQL it's the length of the string (#2536).

  • win_over() escapes expression using current database rules.

Backends

  • copy_to() now uses db_write_table() instead of db_create_table() and db_insert_into(). db_write_table.DBIConnection() uses dbWriteTable().

  • New db_copy_to(), db_compute() and db_collect() allow backends to override the entire database process behind copy_to(), compute() and collect(). db_sql_render() allow additional control over the SQL rendering process.

  • All generics whose behaviour can vary from database to database now provide a DBIConnection method. That means that you can easily scan the NAMESPACE to see the extension points.

  • sql_escape_logical() allows you to control the translation of literal logicals (#2614).

  • src_desc() has been replaced by db_desc() and now dispatches on the connection, eliminating the last method that required dispatch on the class of the src.

  • win_over(), win_rank(), win_recycled(), win_cumulative(), win_current_group() and win_current_order() are now exported. This should make it easier to provide customised SQL for window functions (#2051, #2126).

  • SQL translation for Microsoft SQL Server (@edgararuiz)

  • SQL translation for Apache Hive (@edgararuiz)

  • SQL translation for Apache Impala (@edgararuiz)

Minor bug fixes and improvements

  • collect() once again defaults to return all rows in the data (#1968). This makes it behave the same as as.data.frame() and as_tibble().

  • collect() only regroups by variables present in the data (#2156)

  • collect() will automatically LIMIT the result to the n, the number of rows requested. This will provide the query planner with more information that it may be able to use to improve execution time (#2083).

  • common_by() gets a better error message for unexpected inputs (#2091)

  • copy_to() no longer checks that the table doesn't exist before creation, intead preferring to fall back on the database for error messages. This should reduce both false positives and false negative (#1470)

  • copy_to() now succeeds for MySQL if a character column contains NA (#1975, #2256, #2263, #2381, @demorenoc, @eduardgrebe).

  • copy_to() now returns it's output invisibly (since you're often just calling for the side-effect).

  • distinct() reports improved variable information for SQL backends. This means that it is more likely to work in the middle of a pipeline (#2359).

  • Ungrouped do() on database backends now collects all data locally first (#2392).

  • Call dbFetch() instead of the deprecated fetch() (#2134). Use DBI::dbExecute() for non-query SQL commands (#1912)

  • explain() and show_query() now invisibly return the first argument, making them easier to use inside a pipeline.

  • print.tbl_sql() displays ordering (#2287) and prints table name, if known.

  • print(df, n = Inf) and head(df, n = Inf) now work with remote tables (#2580).

  • db_desc() and sql_translate_env() get defaults for DBIConnection.

  • Formatting now works by overriding the tbl_sum() generic instead of print(). This means that the output is more consistent with tibble, and that format() is now supported also for SQL sources (tidyverse/dbplyr#14).

Lazy ops

  • [API] The signature of op_base has changed to op_base(x, vars, class)

  • [API] translate_sql() and partial_eval() have been refined:

    • translate_sql() no longer takes a vars argument; instead call partial_eval() yourself.

    • Because it no longer needs the environment translate_sql()_ now works with a list of dots, rather than a lazy_dots.

    • partial_eval() now takes a character vector of variable names rather than a tbl.

    • This leads to a simplification of the op data structure: dots is now a list of expressions rather than a lazy_dots.

  • [API] op_vars() now returns a list of quoted expressions. This enables escaping to happen at the correct time (i.e. when the connection is known).

Reference manual

It appears you don't have a PDF plugin for this browser. You can click here to download the reference manual.