pgsql: Doc: document how EXPLAIN ANALYZE reports parallel queries.

Doc: document how EXPLAIN ANALYZE reports parallel queries.

This wasn't covered anywhere before...

Reported-by: Marcos Pegoraro <marcos@f10.com.br>
Author: Maciek Sakrejda <maciek@pganalyze.com>
Reviewed-by: Ilia Evdokimov <ilya.evdokimov@tantorlabs.com>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/CAB-JLwYCgdiB=trauAV1HN5rAWQdvDGgaaY_mqziN88pBTvqqg@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/99d6aa64ef85a736f08b39e4e9b174c9bed035a7

Modified Files
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doc/src/sgml/perform.sgml | 60 +++++++++++++++++++++++++++++++++++++++++++++--
1 file changed, 58 insertions(+), 2 deletions(-)