Run a SPARQL query
Arguments
- con
a ODBC connection to Virtuoso, from
vos_connect()- query
a SPARQL query statement
Details
SPARQL is a graph query language similar in syntax SQL, but allows the use of variables to walk through graph nodes.
Examples
vos_status()
#> virtuoso isn't running.
# \donttest{
if(has_virtuoso()){
vos_start()
con <- vos_connect()
# show first 4 triples in the database
DBI::dbGetQuery(con, "SPARQL SELECT * WHERE { ?s ?p ?o } LIMIT 4")
}
#> Warning: Exiting, virtuoso template not found... is virtuoso installed?
#> PROCESS 'virtuoso-t', running, pid 2884.
#> Server is now starting up, this may take a few seconds...
#> virtuoso isn't running.
#> Error in base::tryCatch(base::withCallingHandlers({ NULL base::saveRDS(base::do.call(base::do.call, base::c(base::readRDS("/tmp/RtmpEoVaWd/callr-fun-844871e13"), base::list(envir = .GlobalEnv, quote = TRUE)), envir = .GlobalEnv, quote = TRUE), file = "/tmp/RtmpEoVaWd/callr-res-829e574f5", compress = FALSE) base::flush(base::stdout()) base::flush(base::stderr()) NULL base::invisible()}, error = function(e) { { callr_data <- base::as.environment("tools:callr")$`__callr_data__` err <- callr_data$err if (FALSE) { base::assign(".Traceback", base::.traceback(4), envir = callr_data) utils::dump.frames("__callr_dump__") base::assign(".Last.dump", .GlobalEnv$`__callr_dump__`, envir = callr_data) base::rm("__callr_dump__", envir = .GlobalEnv) } e <- err$process_call(e) e2 <- err$new_error("error in callr subprocess") class <- base::class class(e2) <- base::c("callr_remote_error", class(e2)) e2 <- err$add_trace_back(e2) cut <- base::which(e2$trace$scope == "global")[1] if (!base::is.na(cut)) { e2$trace <- e2$trace[-(1:cut), ] } base::saveRDS(base::list("error", e2, e), file = base::paste0("/tmp/RtmpEoVaWd/callr-res-829e574f5", ".error")) }}, interrupt = function(e) { { callr_data <- base::as.environment("tools:callr")$`__callr_data__` err <- callr_data$err if (FALSE) { base::assign(".Traceback", base::.traceback(4), envir = callr_data) utils::dump.frames("__callr_dump__") base::assign(".Last.dump", .GlobalEnv$`__callr_dump__`, envir = callr_data) base::rm("__callr_dump__", envir = .GlobalEnv) } e <- err$process_call(e) e2 <- err$new_error("error in callr subprocess") class <- base::class class(e2) <- base::c("callr_remote_error", class(e2)) e2 <- err$add_trace_back(e2) cut <- base::which(e2$trace$scope == "global")[1] if (!base::is.na(cut)) { e2$trace <- e2$trace[-(1:cut), ] } base::saveRDS(base::list("error", e2, e), file = base::paste0("/tmp/RtmpEoVaWd/callr-res-829e574f5", ".error")) }}, callr_message = function(e) { base::try(base::signalCondition(e))}), error = function(e) { NULL if (FALSE) { base::try(base::stop(e)) } else { base::invisible() }}, interrupt = function(e) { NULL if (FALSE) { e } else { base::invisible() }}): ! ODBC failed with error 00000 from [unixODBC][Driver Manager].
#> ✖ Can't open lib 'virtodbc.so' : file not found
#> ℹ From nanodbc/nanodbc.cpp:1150.
# }