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Split the createuniquenodes query in two as MySQL was choosing a very

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bad execution plan for it with the OR condition.
This commit is contained in:
Tom Hughes 2007-08-31 11:14:40 +00:00
parent 0975858cdb
commit 18453600aa
1 changed files with 27 additions and 12 deletions
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39
app/controllers/amf_controller.rb
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@ -691,18 +691,33 @@ end
def createuniquenodes(uqs_name,uqn_name)
# Finds nodes which appear in uniquesegments but no other segments
sql=<<-EOF
CREATE TEMPORARY TABLE #{uqn_name}
SELECT DISTINCT node_id
FROM (SELECT cn.id AS node_id
FROM current_nodes AS cn,
current_segments AS cs,
#{uqs_name} AS us
WHERE cs.id=us.segment_id
AND (cn.id=cs.node_a OR cn.id=cs.node_b)) AS n
LEFT JOIN current_segments AS cs2 ON node_id=cs2.node_a AND cs2.visible=1
LEFT JOIN current_segments AS cs3 ON node_id=cs3.node_b AND cs3.visible=1
WHERE cs2.node_a IS NULL
AND cs3.node_b IS NULL
CREATE TEMPORARY TABLE #{uqn_name}
SELECT DISTINCT node_id
FROM (SELECT cn.id AS node_id
FROM current_nodes AS cn,
current_segments AS cs,
#{uqs_name} AS us
WHERE cs.id=us.segment_id
AND cn.id=cs.node_a) AS n
LEFT JOIN current_segments AS cs2 ON node_id=cs2.node_a AND cs2.visible=1
LEFT JOIN current_segments AS cs3 ON node_id=cs3.node_b AND cs3.visible=1
WHERE cs2.node_a IS NULL
AND cs3.node_b IS NULL
EOF
ActiveRecord::Base.connection.execute(sql)
sql=<<-EOF
INSERT INTO #{uqn_name}
SELECT DISTINCT node_id
FROM (SELECT cn.id AS node_id
FROM current_nodes AS cn,
current_segments AS cs,
#{uqs_name} AS us
WHERE cs.id=us.segment_id
AND cn.id=cs.node_b) AS n
LEFT JOIN current_segments AS cs2 ON node_id=cs2.node_a AND cs2.visible=1
LEFT JOIN current_segments AS cs3 ON node_id=cs3.node_b AND cs3.visible=1
WHERE cs2.node_a IS NULL
AND cs3.node_b IS NULL
EOF
ActiveRecord::Base.connection.execute(sql)
end