NEWS.md

dbplyr (development version)

(To become dbplyr 2.0.0)

dplyr 1.0.0 compatibility

• across() is now translated into individual SQL statements (#480).

• rename() and select() support dplyr 1.0.0 tidyselect syntax (apart from predicate functions which can't easily work on computed queries) (#502).

• relocate() makes it easy to move columns (#494) and rename_with() makes it easy to rename columns programmatically (#502).

• slice_min(), slice_max(), and slice_order() are now supported. slice_head() and slice_tail() throw clear error messages (#394)

SQL generation

• Documentation has been radically improved with new topics for each major verb and each backend giving more details about the SQL translation.

• intersect(), union() and setdiff() gain an all argument to add the ALL argument (#414).

• Join functions gains a na_matches argument that allows you to control whether or not NA (NULL) values match other NA values. The default is "never", which is the usual behaviour in databases. You can set na_matches = "na" to match R's usual join behaviour (#180). Additional arguments error (instead of being silently swallowed) (#382).

• Joins now only use aliases where needed to disambiguate columns; this should make generated queries more readable.

• Subqueries no longer include an ORDER BY clause. This is not part of the SQL spec, and has very limited support across databases. Now such queries generate a warning suggesting that you move your arrange() call later in the pipeline (#276). (There's one exception: ORDER BY is still generated if LIMIT is present; this tends to affect the returns rows but not necessarily their order).

• Subquery names are now scoped within the query. This makes query text deterministic which helps some query optimisers/cachers (#336).

• sql_optimise() now can partially optimise a pipeline; due to an unfortunate bug it previously gave up too easily.

• in_schema() quotes each input individually (#287) (use sql() to opt out of quoting, if needed). And DBI::Id() should work anywhere that in_schema() does.

SQL translation

• Experimental new SAP HANA backend (#233). Requires the latest version of odbc.

• All backends:

  • You can now use :: in translations, so that (e.g.) dbplyr::n() is translated to count(*) (#207).

  • %/% now generates a clear error message; previously it was translated to / which is not correct (#108).

  • n() is translated to count(*) instead of count() (#343).

  • sub_str() translation is more consistent in edge cases (@ianmcook).

  • All median() (@lorenzwalthert, #483), pmin(), pmax() (#479), sd() and var() functions have an na.rm argument that warns once when not TRUE. This makes them consistent with mean() and sum().

  • substring() is now translated the same way as substr() (#378).

• blob vectors can now be used with !! and !!! operators, for example in filter() (@okhoma, #433)

• MySQL uses standard SQL for index creation.

• MS SQL translation does better a distinguishing between bit and boolean (#377, #318). if and ifelse once again generate IIF, creating simpler expressions. as.*() function uses TRY_CAST() instead of CAST() for version 11+ (2012+) (@DavidPatShuiFong, #380).

• odbc no longer translates count(); this was an accidental inclusion.

• Oracle translation now depends on Oracle 12c, and uses a "row-limiting" clause for head(). It gains translations for today() and now(), and improved as.Date() translation (@rlh1994, #267).

• PostgreSQL: new translations for lubridate period functions years(), months(), days(), and floor_date() (@bkkkk, #333) and stringr functions str_squish(), str_remove(), and str_remove_all() (@shosaco).

• New RedShift translations when used with RPostgres::Redshift().

  • str_replace() errors since there's no Redshift translation, and str_replace_all() uses REGEXP_REPLACE() (#446).

  • paste() and paste0() use || (#458).

  • as.numeric() and as.double() cast to FLOAT (#408).

  • substr() and str_sub() use SUBSTRING() (#327).

• SQLite gains translations for lubridate functions today(), now(), year(), month(), day(), hour(), minute(), second(),yday() (#262), and correct translation for median() (#357).

Extensibility

If you are the author of a dbplyr backend, please see vignette("backend-2") for details.

• New dbplyr_edition() generic allows you to opt-in to the 2nd edition of the dbplyr API.

• db_write_table() now calls DBI::dbWriteTable() instead of nine generics that formerly each did a small part: db_create_indexes(), db_begin(), db_rollback(), db_commit(), db_list_tables(), drop_drop_table(), db_has_table(), db_create_table(), and db_data_types(). You can now delete the methods for these generics.

  db_query_rows() is no longer used; it appears that it hasn't been used for some time, so if you have a method, you can delete it.

• DBI::dbQuoteIdentifier() is now used instead of sql_escape_ident() and DBI::dbQuoteString() instead of sql_escape_string().

• A number of db_* generics have been replaced with new SQL generation generics:

  • dplyr::db_analyze() -> dbplyr::sql_table_analyze()
  • dplyr::db_create_index() -> dbplyr::sql_table_index()
  • dplyr::db_explain() -> dbplyr::sql_queriy_explain()
  • dplyr::db_query_fields() -> dbplyr::sql_query_fields()
  • dplyr::db_save_query() -> dbplyr::sql_query_save()

  This makes them easier to test and is an important part of the process of moving all database generics in dbplyr (#284).

• A number of other generics have been renamed to facilitate the move from dplyr to dbplyr:

  • dplyr::sql_select() -> dbplyr::sql_query_select()
  • dplyr::sql_join() -> dbplyr::sql_query_join()
  • dplyr::sql_semi_join() -> dbplyr::sql_query_semi_join()
  • dplyr::sql_set_op() -> dbplyr::sql_query_set_op()
  • dplyr::sql_subquery() -> dbplyr::sql_query_wrap()
  • dplyr::db_desc() -> dbplyr::db_connection_describe()

• New db_temporary_table() generic makes it easier to work with databases that require temporary tables to be specially named.

• New sql_expr_matches() generic allows databases to use more efficient alternatives when determine if two values "match" (i.e. like equality but a pair of NULLs will also match). For more details, see https://modern-sql.com/feature/is-distinct-from

• New sql_join_suffix() allows backends to control the default suffixes used (#254).

Minor improvements and bug fixes

• All old lazy eval shims have been removed. These have been deprecated for some time.

• Date-time escaping methods for Athena and Presto have moved to the packages where they belong.

• Attempting to embed a Shiny reactive in a query now gives a helpful error (#439).

• copy_lahman() and copy_nycflights13() (and hence nycflights13_sqlite()) and friends now return DBI connections rather than the now deprecated src_dbi() (#440).

• copy_to() can now overwrite when table is specified with schema (#489), and gains an in_transaction argument used to optionally suppress the transaction wrapper (#368).

• distinct() no longer duplicates column if grouped (#354).

• transmute() now correctly tracks variables it needs when creating subqueries (#313).

• mutate() grouping variables no longer generates a downstream error (#396)

• mutate() correctly generates subqueries when you re-use the same variable three or more times (#412).

• window_order() overrides ordering, rather than appending to it.

dbplyr 1.4.4

• Internally DBI::dbExecute() now uses immediate = TRUE; this improves support for session-scoped temporary tables in MS SQL (@krlmlr, #438).

• Subqueries with ORDER BY use TOP 9223372036854775807 instead of TOP 100 PERCENT on SQL Server for compatibility with Azure Data Warehouse (#337, @alexkyllo).

• escape() now supports blob vectors using new sql_escape_raw() generic. It enables using blob variables in dplyr verbs, for example to filter nvarchar values by UTF-16 blobs (see https://github.com/r-dbi/DBI/issues/215#issuecomment-356376133). (@okhoma, #433)

• Added setOldClass() calls for "ident" and "ident_q" classes for compatibility with dplyr 1.0.0 (#448, @krlmlr).

• Postgres str_detect() translation uses same argument names as stringr, and gains a negate argument (#444).

• semi_join() and anti_join() now correctly support the sql_on argument (#443, @krlmlr).

dbplyr 1.4.3

• dbplyr now uses RPostgres (instead of RPostgreSQL) and RMariaDB (instead of RMySQL) for its internal tests and data functions (#427).

• The Date and POSIXt methods for escape() now use exported sql_escape_date() and sql_escape_datetime() generics to allow backend specific formatting of date and datetime literals. These are used to provide methods for Athena and Presto backends (@OssiLehtinen, #384, #391).

• first(), last(), nth(), lead() and lag() now respect the window_frame() (@krlmlr, #366).

• SQL server: new translations for str_flatten() (@PauloJhonny, #405).

• SQL server: temporary datasets are now session-local, not global (#401).

• Postgres: correct str_detect(), str_replace() and str_replace_all() translation (@shosaco, #362).

dbplyr 1.4.2

• Fix bug when partially evaluating unquoting quosure containing a single symbol (#317)

• Fixes for rlang and dpylr compatibility.

dbplyr 1.4.1

Minor improvements to SQL generation

• x %in% y strips names of y (#269).

• Enhancements for scoped verbs (mutate_all(), summarise_if(), filter_at() etc) (#296, #306).

• MS SQL use TOP 100 PERCENT as stop-gap to allow subqueries with ORDER BY (#277).

• Window functions now translated correctly for Hive (#293, @cderv).

dbplyr 1.4.0

Breaking changes

• Error: `con` must not be NULL: If you see this error, it probably means that you have forgotten to pass con down to a dbplyr function. Previously, dbplyr defaulted to using simulate_dbi() which introduced subtle escaping bugs. (It's also possible I have forgotten to pass it somewhere that the dbplyr tests don't pick up, so if you can't figure it out, please let me know).

• Subsetting ([[, $, and [) functions are no longer evaluated locally. This makes the translation more consistent and enables useful new idioms for modern databases (#200).

New features

• MySQL/MariaDB (https://mariadb.com/kb/en/library/window-functions/) and SQLite (https://www.sqlite.org/windowfunctions.html) translations gain support for window functions, available in Maria DB 10.2, MySQL 8.0, and SQLite 3.25 (#191).

• Overall, dplyr generates many fewer subqueries:

  • Joins and semi-joins no longer add an unneeded subquery (#236). This is facilitated by the new bare_identifier_ok argument to sql_render(); the previous argument was called root and confused me.

  • Many sequences of select(), rename(), mutate(), and transmute() can be collapsed into a single query, instead of always generating a subquery (#213).

• New vignette("sql") describes some advantages of dbplyr over SQL (#205) and gives some advice about writing literal SQL inside of dplyr, when you need to (#196).

• New vignette("reprex") gives some hints on creating reprexes that work anywhere (#117). This is supported by a new tbl_memdb() that matches the existing tbl_lazy().

• All ..._join() functions gain an sql_on argument that allows specifying arbitrary join predicates in SQL code (#146, @krlmlr).

SQL translations

• New translations for some lubridate functions: today(), now(), year(), month(), day(), hour(), minute(), second(), quarter(), yday() (@colearendt, @derekmorr). Also added new translation for as.POSIXct().

• New translations for stringr functions: str_c(), str_sub(), str_length(), str_to_upper(), str_to_lower(), and str_to_title() (@colearendt). Non-translated stringr functions throw a clear error.

• New translations for bitwise operations: bitwNot(), bitwAnd(), bitwOr(), bitwXor(), bitwShiftL(), and bitwShiftR(). Unlike the base R functions, the translations do not coerce arguments to integers (@davidchall, #235).

• New translation for x[y] to CASE WHEN y THEN x END. This enables sum(a[b == 0]) to work as you expect from R (#202). y needs to be a logical expression; if not you will likely get a type error from your database.

• New translations for x$y and x[["y"]] to x.y, enabling you to index into nested fields in databases that provide them (#158).

• The .data and .env pronouns of tidy evaluation are correctly translated (#132).

• New translation for median() and quantile(). Works for all ANSI compliant databases (SQL Server, Postgres, MariaDB, Teradata) and has custom translations for Hive. Thanks to @edavidaja for researching the SQL variants! (#169)

• na_if() is correct translated to NULLIF() (rather than NULL_IF) (#211).

• n_distinct() translation throws an error when given more than one argument. (#101, #133).

• New default translations for paste(), paste0(), and the hyperbolic functions (these previously were only available for ODBC databases).

• Corrected translations of pmin() and pmax() to LEAST() and GREATEST() for ANSI compliant databases (#118), to MIN() and MAX() for SQLite, and to an error for SQL server.

• New translation for switch() to the simple form of CASE WHEN (#192).

SQL simulation

SQL simulation makes it possible to see what dbplyr will translate SQL to, without having an active database connection, and is used for testing and generating reprexes.

• SQL simulation has been overhauled. It now works reliably, is better documented, and always uses ANSI escaping (i.e. ` for field names and ' for strings).

• tbl_lazy() now actually puts a dbplyr::src in the $src field. This shouldn't affect any downstream code unless you were previously working around this weird difference between tbl_lazy and tbl_sql classes. It also includes the src class in its class, and when printed, shows the generated SQL (#111).

Database specific improvements

• MySQL/MariaDB

  • Translations also applied to connections via the odbc package (@colearendt, #238)

  • Basic support for regular expressions via str_detect() and
    str_replace_all() (@colearendt, #168).

  • Improved translation for as.logical(x) to IF(x, TRUE, FALSE).

• Oracle

  • New custom translation for paste() and paste0() (@cderv, #221)

• Postgres

  • Basic support for regular expressions via str_detect() and
    str_replace_all() (@colearendt, #168).

• SQLite

  • explain() translation now generates EXPLAIN QUERY PLAN which generates a higher-level, more human friendly explanation.

• SQL server

  • Improved translation for as.logical(x) to CAST(x as BIT) (#250).

  • Translates paste(), paste0(), and str_c() to +.

  • copy_to() method applies temporary table name transformation earlier so that you can now overwrite temporary tables (#258).

  • db_write_table() method uses correct argument name for passing along field types (#251).

Minor improvements and bug fixes

• Aggregation functions only warn once per session about the use of na.rm = TRUE (#216).

• table names generated by random_table_name() have the prefix "dbplyr_", which makes it easier to find them programmatically (@mattle24, #111)

• Functions that are only available in a windowed (mutate()) query now throw an error when called in a aggregate (summarise()) query (#129)

• arrange() understands the .by_group argument, making it possible sort by groups if desired. The default is FALSE (#115)

• distinct() now handles computed variables like distinct(df, y = x + y) (#154).

• escape(), sql_expr() and build_sql() no longer accept con = NULL as a shortcut for con = simulate_dbi(). This made it too easy to forget to pass con along, introducing extremely subtle escaping bugs. win_over() gains a con argument for the same reason.

• New escape_ansi() always uses ANSI SQL 92 standard escaping (for use in examples and documentation).

• mutate(df, x = NULL) drops x from the output, just like when working with local data frames (#194).

• partial_eval() processes inlined functions (including rlang lambda functions). This makes dbplyr work with more forms of scoped verbs like df %>% summarise_all(~ mean(.)), df %>% summarise_all(list(mean)) (#134).

• sql_aggregate() now takes an optional argument f_r for passing to check_na_rm(). This allows the warning to show the R function name rather than the SQL function name (@sverchkov, #153).

• sql_infix() gains a pad argument for the rare operator that doesn't need to be surrounded by spaces.

• sql_prefix() no longer turns SQL functions into uppercase, allowing for correct translation of case-sensitive SQL functions (#181, @mtoto).

• summarise() gives a clear error message if you refer to a variable created in that same summarise() (#114).

• New sql_call2() which is to rlang::call2() as sql_expr() is to rlang::expr().

• show_query() and explain() use cat() rather than message.

• union(), union_all(), setdiff() and intersect() do a better job of matching columns across backends (#183).

dbplyr 1.3.0

• Now supports for dplyr 0.8.0 (#190) and R 3.1.0

API changes

• Calls of the form dplyr::foo() are now evaluated in the database, rather than locally (#197).

• vars argument to tbl_sql() has been formally deprecated; it hasn't actually done anything for a while (#3254).

• src and tbl objects now include a class generated from the class of the underlying connection object. This makes it possible for dplyr backends to implement different behaviour at the dplyr level, when needed. (#2293)

SQL translation

• x %in% y is now translated to FALSE if y is empty (@mgirlich, #160).

• New as.integer64(x) translation to CAST(x AS BIGINT) (#3305)

• case_when now translates with a ELSE clause if a formula of the form TRUE~<RHS> is provided . (@cderv, #112)

• cummean() now generates AVG() not MEAN() (#157)

• str_detect() now uses correct parameter order (#3397)

• MS SQL

  • Cumulative summary functions now work (#157)
  • ifelse() uses CASE WHEN instead of IIF; this allows more complex operations, such as %in%, to work properly (#93)

• Oracle

  • Custom db_drop_table() now only drops tables if they exist (#3306)
  • Custom setdiff() translation (#3493)
  • Custom db_explain() translation (#3471)

• SQLite

  • Correct translation for as.numeric()/as.double() (@chris-park, #171).

• Redshift

  • substr() translation improved (#3339)

Minor improvements and bug fixes

• copy_to() will only remove existing table when overwrite = TRUE and the table already exists, eliminating a confusing "NOTICE" from PostgreSQL (#3197).

• partial_eval() handles unevaluated formulas (#184).

• pull.tbl_sql() now extracts correctly from grouped tables (#3562).

• sql_render.op() now correctly forwards the con argument (@kevinykuo, #73).

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)

• Oracle: changed VARVHAR to VARCHAR2 datatype (@washcycle, #66)

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 translators 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, instead 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).