library(DBI)

conn <- dbConnect(drv = RPostgres::Postgres(),
                  dbname = "my_db",
                  host = "localhost",
                  user = "db_admin",
                  password = pw)

rm(pw)

mydf <- data.frame(column_1 = c("A", "B", "C"), column_2 = c(1, Inf, 3))

dbWriteTable(conn, "mytable", mydf, row.names = FALSE)

from_df <- dbReadTable(conn, "mytable")

from_df

  column_1 column_2
1        A        1
2        B        0
3        C        3

R version 4.0.3 (2020-10-10)
Platform: x86_64-w64-mingw32/x64 (64-bit)
Running under: Windows 10 x64 (build 17763)

Matrix products: default

locale:
[1] LC_COLLATE=French_France.1252  LC_CTYPE=French_France.1252   
[3] LC_MONETARY=French_France.1252 LC_NUMERIC=C                  
[5] LC_TIME=French_France.1252    

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     

other attached packages:
[1] RPostgreSQL_0.6-2 DBI_1.1.0        

loaded via a namespace (and not attached):
 [1] bit_4.0.4       compiler_4.0.3  hms_0.5.3       tools_4.0.3    
 [5] Rcpp_1.0.5      bit64_4.0.5     vctrs_0.3.4     blob_1.2.1     
 [9] pkgconfig_2.0.3 rlang_0.4.8     RPostgres_1.2.1 fortunes_1.5-4