Hi MonetDB developers,
I have a question about RDF data management in MonetDB/SQL. The comment of
sql.rdfshred says "shredding an RDF data file from location results in 7 new
tables (6 permutations of SPO and a mapping) ... We can then query with SQL
queries the RDF triple store by quering tables gid_spo, gid_pso etc., ...". In
my option, if the spo table is considered the triples table, the other 5 tables
(sop, pso, pos, osp, ops) (except the mapping table) can be viewed as indexes
of the triples table spo.
When I write SQL to query the shredded RDF data in the triples table, I have
two ways. The first way is to only use spo table to make self-joins. The second
way is to use all 6 tables to make joins. I noticed that "MonetDB/SQL Reference
Manual" says that "The heart is the MonetDB server, which comes with the
following innovative features. ... Index selection, creation and maintenance is
automatic". If I use 6 tables (as indexes) explicitly to make joins, it seems
that I write the query plan by myself. However, I think this work should be
done by the SQL optimizer using statistics from the system catalog. I wondered
if these tables have already been specified as indexes in the internal code, or
if there is a way to specify it so that the optimizer can use them as indexes
to generate query plans. I am not sure if my understanding is correct. I will
appreciate any help from developers. Thank you in advance.
Best regards,
Xin Wang
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