explain

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Explain details of a tbl.

This is a generic function which gives more details about an object than print, and is more focussed on human readable output than str.

Usage
explain(x, ...)

show_query(x)

Arguments
x

An object to explain

...

Other parameters possibly used by generic

Databases

Explaining a tbl_sql will run the SQL EXPLAIN command which will describe the query plan. This requires a little bit of knowledge about how EXPLAIN works for your database, but is very useful for diagnosing performance problems.

Aliases
  • explain
  • show_query
Examples
library(dplyr) if (require("RSQLite") && has_lahman("sqlite")) { lahman_s <- lahman_sqlite() batting <- tbl(lahman_s, "Batting") batting %>% show_query() batting %>% explain() # The batting database has indices on all ID variables: # SQLite automatically picks the most restrictive index batting %>% filter(lgID == "NL" & yearID == 2000L) %>% explain() # OR's will use multiple indexes batting %>% filter(lgID == "NL" | yearID == 2000) %>% explain() # Joins will use indexes in both tables teams <- tbl(lahman_s, "Teams") batting %>% left_join(teams, c("yearID", "teamID")) %>% explain() }
Documentation reproduced from package dplyr, version 0.5.0, License: MIT + file LICENSE

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