### Problem (see attempted solution below)
When preloading my VOS docker container, I have an adaptation of [this example posted by @PvK](https://community.openlinksw.com/t/how-to-bulk-load-data-into-a-virtuoso-docker-instance/3248), where parallelization is achieved with multiple backgrounded calls to `rdf_loader_run ()` which is detailed in the ninth code block of the [RDF Bulk Load Utility documentation](https://docs.openlinksw.com/virtuoso/rdfperfloading/#rdfperfloadingutility).
```
--
--  Add the gzipped dumps
--
ld_dir_all ('data', '*.owl.gz', 'http://pathwaycommons.org/pc12');
ld_dir_all ('data', '*.ttl.gz', 'http://nextprot.org/rdf');
ld_dir_all ('data', '*.rdf', 'http://www.biopax.org/release/biopax-level3.owl#');
--
--  run rdf bulk loader
--
rdf_loader_run () &
rdf_loader_run () &
rdf_loader_run () &
rdf_loader_run () &
rdf_loader_run () &
rdf_loader_run () &
rdf_loader_run () &
rdf_loader_run () &
--
--  synchronize
--
wait_for_children;
checkpoint;
--  End of script
--
```

During preload the script above generates an error `PL LOG: Error in autoexec.isql: [37000] SQ074: Line 5: syntax error`, causing the files to be skipped, here is the full PL output for that script:
```
MKK_vtest2     | * Running SQL script: [/opt/virtuoso-opensource/initdb.d/09-bulkload-rdf.sql]
MKK_vtest2     | 
MKK_vtest2     |                Thu Feb 16 2023
MKK_vtest2     | 20:28:24 { Loading plugin 1: Type `plain', file `geos' in `../hosting'
MKK_vtest2     | 20:28:24   plain version 1.2.3235 from OpenLink Software
MKK_vtest2     | 20:28:24   GEOS plugin based on Geometry Engine Open Source library from Open Source Geospatial Foundation
MKK_vtest2     | 20:28:24   SUCCESS plugin 1: loaded from ../hosting/geos.so }
MKK_vtest2     | 20:28:24 { Loading plugin 2: Type `plain', file `graphql' in `../hosting'
MKK_vtest2     | 20:28:24   GraphQL/SPARQL Bridge version 0.9.1 (64e6ecd39) from OpenLink Software
MKK_vtest2     | 20:28:24   Support functions for GraphQL/SPARQL Bridge
MKK_vtest2     | 20:28:24   SUCCESS plugin 2: loaded from ../hosting/graphql.so }
MKK_vtest2     | 20:28:24 { Loading plugin 3: Type `plain', file `proj4' in `../hosting'
MKK_vtest2     | 20:28:24   plain version 1.1.3235 from OpenLink Software
MKK_vtest2     | 20:28:24   Cartographic Projections support based on Frank Warmerdam's proj4 library
MKK_vtest2     | 20:28:24   SUCCESS plugin 3: loaded from ../hosting/proj4.so }
MKK_vtest2     | 20:28:24 { Loading plugin 4: Type `plain', file `shapefileio' in `../hosting'
MKK_vtest2     | 20:28:24   ShapefileIO version 0.1virt71 from OpenLink Software
MKK_vtest2     | 20:28:24   Shapefile support based on Frank Warmerdam's Shapelib
MKK_vtest2     | 20:28:24   SUCCESS plugin 4: loaded from ../hosting/shapefileio.so }
MKK_vtest2     | 20:28:24 OpenLink Virtuoso Universal Server
MKK_vtest2     | 20:28:24 Version 07.20.3235-pthreads for Linux as of Oct 19 2022
MKK_vtest2     | 20:28:24 uses OpenSSL 1.1.1  11 Sep 2018
MKK_vtest2     | 20:28:24 uses parts of PCRE, Html Tidy
MKK_vtest2     | 20:28:28 Database version 3126
MKK_vtest2     | 20:28:28 SQL Optimizer enabled (max 1000 layouts)
MKK_vtest2     | 20:28:30 Compiler unit is timed at 0.000125 msec
MKK_vtest2     | 20:28:30 Roll forward started
MKK_vtest2     | 20:28:30 Roll forward complete
MKK_vtest2     | 20:28:31 PL LOG: Error in autoexec.isql: [37000] SQ074: Line 5: syntax error
MKK_vtest2     | 20:28:31 Checkpoint started
MKK_vtest2     | 20:28:31 Checkpoint finished, log reused
MKK_vtest2     | 20:28:32 Checkpoint started
MKK_vtest2     | 20:28:32 Checkpoint finished, log reused
MKK_vtest2     | 20:28:32 Server exiting
MKK_vtest2     | Setting passwords
```
### Attempt to solve

I investigated this error by re-running the bulk load script above interactively, after allowing PL to complete and logging into conductor on the running container.  Notice that the first three calls to `ld_dir` complete successfully, but the first call to `rdf_loader_run` fails:
```
The statement execution did not return a result set.
The statement execution did not return a result set.
The statement execution did not return a result set.

SQLState: 37000

Message: SQ074: Line 5: syntax error

--
--  run rdf bulk loader
--
rdf_loader_run () &
rdf_loader_run () &
rdf_loader_run () &
rdf_loader_run () &
rdf_loader_run () &
rdf_loader_run () &
rdf_loader_run () &
rdf_loader_run () &
--
--  synchronize
--
wait_for_children 
```

It appears that the backgrounding operator `&` is the issue, since the following fragment executes as expected in isql (although I did not wait for it to complete):
```
ld_dir_all ('data', '*.rdf', 'http://www.biopax.org/release/biopax-level3.owl#');
--
--  run rdf bulk loader
--
rdf_loader_run ();
```
error when backgrounding rdf_loader_run () in isql
This is a GitHub Issue
repo:virtuoso-opensource
owner:openlink
Title : error when backgrounding rdf_loader_run () in isql
Issue date:

--- start body ---
### Problem (see attempted solution below)
When preloading my VOS docker container, I have an adaptation of [this example posted by @PvK](https://community.openlinksw.com/t/how-to-bulk-load-data-into-a-virtuoso-docker-instance/3248), where parallelization is achieved with multiple backgrounded calls to `rdf_loader_run ()` which is detailed in the ninth code block of the [RDF Bulk Load Utility documentation](https://docs.openlinksw.com/virtuoso/rdfperfloading/#rdfperfloadingutility).
```
--
--  Add the gzipped dumps
--
ld_dir_all ('data', '*.owl.gz', 'http://pathwaycommons.org/pc12');
ld_dir_all ('data', '*.ttl.gz', 'http://nextprot.org/rdf');
ld_dir_all ('data', '*.rdf', 'http://www.biopax.org/release/biopax-level3.owl#');
--
--  run rdf bulk loader
--
rdf_loader_run () &
rdf_loader_run () &
rdf_loader_run () &
rdf_loader_run () &
rdf_loader_run () &
rdf_loader_run () &
rdf_loader_run () &
rdf_loader_run () &
--
--  synchronize
--
wait_for_children;
checkpoint;
--  End of script
--
```

During preload the script above generates an error `PL LOG: Error in autoexec.isql: [37000] SQ074: Line 5: syntax error`, causing the files to be skipped, here is the full PL output for that script:
```
MKK_vtest2     | * Running SQL script: [/opt/virtuoso-opensource/initdb.d/09-bulkload-rdf.sql]
MKK_vtest2     | 
MKK_vtest2     |                Thu Feb 16 2023
MKK_vtest2     | 20:28:24 { Loading plugin 1: Type `plain', file `geos' in `../hosting'
MKK_vtest2     | 20:28:24   plain version 1.2.3235 from OpenLink Software
MKK_vtest2     | 20:28:24   GEOS plugin based on Geometry Engine Open Source library from Open Source Geospatial Foundation
MKK_vtest2     | 20:28:24   SUCCESS plugin 1: loaded from ../hosting/geos.so }
MKK_vtest2     | 20:28:24 { Loading plugin 2: Type `plain', file `graphql' in `../hosting'
MKK_vtest2     | 20:28:24   GraphQL/SPARQL Bridge version 0.9.1 (64e6ecd39) from OpenLink Software
MKK_vtest2     | 20:28:24   Support functions for GraphQL/SPARQL Bridge
MKK_vtest2     | 20:28:24   SUCCESS plugin 2: loaded from ../hosting/graphql.so }
MKK_vtest2     | 20:28:24 { Loading plugin 3: Type `plain', file `proj4' in `../hosting'
MKK_vtest2     | 20:28:24   plain version 1.1.3235 from OpenLink Software
MKK_vtest2     | 20:28:24   Cartographic Projections support based on Frank Warmerdam's proj4 library
MKK_vtest2     | 20:28:24   SUCCESS plugin 3: loaded from ../hosting/proj4.so }
MKK_vtest2     | 20:28:24 { Loading plugin 4: Type `plain', file `shapefileio' in `../hosting'
MKK_vtest2     | 20:28:24   ShapefileIO version 0.1virt71 from OpenLink Software
MKK_vtest2     | 20:28:24   Shapefile support based on Frank Warmerdam's Shapelib
MKK_vtest2     | 20:28:24   SUCCESS plugin 4: loaded from ../hosting/shapefileio.so }
MKK_vtest2     | 20:28:24 OpenLink Virtuoso Universal Server
MKK_vtest2     | 20:28:24 Version 07.20.3235-pthreads for Linux as of Oct 19 2022
MKK_vtest2     | 20:28:24 uses OpenSSL 1.1.1  11 Sep 2018
MKK_vtest2     | 20:28:24 uses parts of PCRE, Html Tidy
MKK_vtest2     | 20:28:28 Database version 3126
MKK_vtest2     | 20:28:28 SQL Optimizer enabled (max 1000 layouts)
MKK_vtest2     | 20:28:30 Compiler unit is timed at 0.000125 msec
MKK_vtest2     | 20:28:30 Roll forward started
MKK_vtest2     | 20:28:30 Roll forward complete
MKK_vtest2     | 20:28:31 PL LOG: Error in autoexec.isql: [37000] SQ074: Line 5: syntax error
MKK_vtest2     | 20:28:31 Checkpoint started
MKK_vtest2     | 20:28:31 Checkpoint finished, log reused
MKK_vtest2     | 20:28:32 Checkpoint started
MKK_vtest2     | 20:28:32 Checkpoint finished, log reused
MKK_vtest2     | 20:28:32 Server exiting
MKK_vtest2     | Setting passwords
```
### Attempt to solve

I investigated this error by re-running the bulk load script above interactively, after allowing PL to complete and logging into conductor on the running container.  Notice that the first three calls to `ld_dir` complete successfully, but the first call to `rdf_loader_run` fails:
```
The statement execution did not return a result set.
The statement execution did not return a result set.
The statement execution did not return a result set.

SQLState: 37000

Message: SQ074: Line 5: syntax error

--
--  run rdf bulk loader
--
rdf_loader_run () &
rdf_loader_run () &
rdf_loader_run () &
rdf_loader_run () &
rdf_loader_run () &
rdf_loader_run () &
rdf_loader_run () &
rdf_loader_run () &
--
--  synchronize
--
wait_for_children 
```

It appears that the backgrounding operator `&` is the issue, since the following fragment executes as expected in isql (although I did not wait for it to complete):
```
ld_dir_all ('data', '*.rdf', 'http://www.biopax.org/release/biopax-level3.owl#');
--
--  run rdf bulk loader
--
rdf_loader_run ();
```
--- end body ---

None