Restrict table alias length

[mgirlich]

Databases have limits on the length of a table alias (e.g Postgres has 63). The table alias should therefore be shortened to not exceed this length but still be unique.

library(dplyr)

con <- DBI::dbConnect(RPostgres::Postgres())

nm1 <- strrep("a", 63)
DBI::dbWriteTable(con, nm1, tibble(x = 1))
df1 <- tbl(con, nm1)

nm2 <- strrep("b", 63)
DBI::dbWriteTable(con, nm2, tibble(x = 1))
df2 <- tbl(con, nm2)

left_join(df1, df1) |> show_query()
#> Joining, by = "x"
#> <SQL>
#> SELECT "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa_LHS"."x" AS "x"
#> FROM "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa" AS "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa_LHS"
#> LEFT JOIN "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa" AS "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa_RHS"
#>   ON ("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa_LHS"."x" = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa_RHS"."x")
left_join(df1, df1)
#> Joining, by = "x"
#> NOTICE:  identifier "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa_LHS" will be truncated to "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
#> 
#> NOTICE:  identifier "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa_LHS" will be truncated to "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
#> NOTICE:  identifier "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa_RHS" will be truncated to "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
#> NOTICE:  identifier "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa_LHS" will be truncated to "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
#> NOTICE:  identifier "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa_RHS" will be truncated to "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
#> Error in `collect()`:
#> ! Failed to collect lazy table.
#> Caused by error:
#> ! Failed to prepare query: ERROR:  table name "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa" specified more than once

^{Created on 2023-01-12 with reprex v2.0.2}

[fh-mthomson]

@mgirlich I've opened #1097 with a proposal to address this.