This is a generic function which gives more details about an object than
print(), and is more focused on human readable output than
explain(x, ...) show_query(x, ...)
An object to explain
Other parameters possibly used by generic
The first argument, invisibly.
tbl_sql will run the SQL
EXPLAIN command which
will describe the query plan. This requires a little bit of knowledge about
EXPLAIN works for your database, but is very useful for
diagnosing performance problems.
lahman_s <- dbplyr::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()
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