title: Case-sensitivity with dplyr + RPostgreSQL string matching
body: <p>I can't figure out how to apply a non-case-sensitive filter query to a remote PostgreSQL table using <code>dplyr</code>.  To demonstrate:</p>
  
  <pre><code>require(dplyr)
  require(stringr)
  require(RPostgreSQL)
  
  drv &lt;- dbDriver("PostgreSQL")
  con &lt;- dbConnect(drv, dbname="mydb", host="localhost", port=5432, user="username")
  
  # create db table
  copy_to(con, iris, "iris", temporary = FALSE)
  
  # dplyr remote database table
  iris_pg &lt;- tbl(con, "iris")
  
  iris_pg %&gt;% filter(str_detect(Species, 'setosa')) %&gt;% head(3) %&gt;% collect()
  # A tibble: 3 x 5
    Sepal.Length Sepal.Width Petal.Length Petal.Width Species
  *        &lt;dbl&gt;       &lt;dbl&gt;        &lt;dbl&gt;       &lt;dbl&gt; &lt;chr&gt;  
  1          5.1         3.5          1.4         0.2 setosa 
  2          4.9         3            1.4         0.2 setosa 
  3          4.7         3.2          1.3         0.2 setosa
  
  iris_pg %&gt;% filter(str_detect(Species, 'Setosa')) %&gt;% head(3) %&gt;% collect()
  # A tibble: 0 x 0
  </code></pre>
  
  <p>To ignore case <code>stringr::fixed('Setosa', ignore_case=TRUE)</code> works with tibble filtering. But with the postgres table it has no effect:</p>
  
  <pre><code>iris_pg %&gt;% filter(str_detect(Species, stringr::fixed('SETOSA', ignore_case=TRUE))) %&gt;% head(3) %&gt;% collect()
  # A tibble: 0 x 0
  </code></pre>
  
  <p>Is anyone aware of a workaround?</p>