require(RPostgreSQL)
drv <- dbDriver("PostgreSQL")
con <- dbConnect(drv, dbname = "")
dbGetquery(con, "SELECT rid, rast, filename FROM schema.capri")

library('raster')
library('rgdal')

dsn="PG:dbname='plots' host=localhost user='test' password='test' port=5432 schema='gisdata' table='map' mode=2"

ras <- readGDAL(dsn) # Get your file as SpatialGridDataFrame
ras2 <- raster(ras,1) # Convert the first Band to Raster
plot(ras2)