Solr 4.6.0 DataImportHandler speed up performance - mysql

Question

I am using Solr 4.6.0, indexing about 10'000 elements at a time and I suffer bad import performance. That means that importing those 10'000 documents takes about 10 minutes. Of course I know, that this hardly depends on the server hardware, but I still would like to know, how any performance boosts could be done and which of them are actually useful in real-world situations (joins etc.)? I am also very thankful for precise examples and not just links to the official documentation.
Here is the data-config.xml
<dataConfig>
<dataSource name="mysql" type="JdbcDataSource"
driver="com.mysql.jdbc.Driver"
url="jdbc:mysql://xxxx"
batchSize="-1"
user="xxxx" password="xxxx" />
<document name="publications">
<entity name="publication" transformer="RegexTransformer" pk="id" query="
SELECT
sm_publications.id AS p_id,
CONCAT(sm_publications.title, ' ', sm_publications.abstract) AS p_text,
sm_publications.year AS p_year,
sm_publications.doi AS p_doi,
sm_conferences.full_name AS c_fullname,
sm_journals.full_name AS j_fullname,
GROUP_CONCAT(DISTINCT sm_query_publications.query_id SEPARATOR '_-_-_-_-_') AS q_id
FROM sm_publications
LEFT JOIN sm_conferences ON sm_conferences.id = sm_publications.conference_id
LEFT JOIN sm_journals ON sm_journals.id = sm_publications.journal_id
INNER JOIN sm_query_publications ON sm_query_publications.publication_id = sm_publications.id
WHERE '${dataimporter.request.clean}' != 'false' OR
sm_publications.modified > '${dataimporter.last_index_time}' GROUP BY sm_publications.id">
<field column="p_id" name="id" />
<field column="p_text" name="text" />
<field column="p_text" name="text_tv" />
<field column="p_year" name="year" />
<field column="p_doi" name="doi" />
<field column="c_fullname" name="conference" />
<field column="j_fullname" name="journal" />
<field column="q_id" name="queries" splitBy="_-_-_-_-_" />
<entity name="publication_authors" query="
SELECT
CONCAT(
IF(sm_authors.first_name != '',sm_authors.first_name,''),
IF(sm_authors.middle_name != '',CONCAT(' ',sm_authors.middle_name),''),
IF(sm_authors.last_name != '',CONCAT(' ',sm_authors.last_name),'')
) AS a_name,
sm_affiliations.display_name AS aa_display_name,
CONCAT(sm_affiliations.latitude, ',', sm_affiliations.longitude) AS aa_geo,
sm_affiliations.country_name AS aa_country_name
FROM sm_publication_authors
INNER JOIN sm_authors ON sm_authors.id = sm_publication_authors.author_id
LEFT JOIN sm_affiliations ON sm_affiliations.id = sm_authors.affiliation_id
WHERE sm_publication_authors.publication_id = '${publication.p_id}'">
<field column="a_name" name="authors" />
<field column="aa_display_name" name="affiliations" />
<field column="aa_geo" name="geo" />
<field column="aa_country_name" name="countries" />
</entity>
<entity name="publication_keywords" query="
SELECT sm_keywords.name FROM sm_publication_keywords
INNER JOIN sm_keywords ON sm_keywords.id = sm_publication_keywords.keyword_id
WHERE sm_publication_keywords.publication_id = '${publication.p_id}'">
<field column="name" name="keywords" />
</entity>
</entity>
</document>
</dataConfig>

Answer 1

By query caching, I meant the CachedSqlEntityProcessor. I favor the merged solution as in your other question MySQL GROUP_CONCAT duplicate entries. But CachedSqlEntityProcessor will help too, if p_id repeated over and over in the resultset of the main query publication_authors, and you have less concern on the extra memory usage.
Update: It looks like you have two other questions solved, probably you can go either way, I post the short example/pointer as you requested anyway in case others find it handy to have
<entity name="x" query="select * from x">
<entity name="y" query="select * from y" processor="CachedSqlEntityProcessor" where="xid=x.id">
</entity>
<entity>
This example was taken from wiki. This will still run each query "select * from y where xid=id" per id from the main query "select * from x". But it won't send in the same query repeatedly.