Periodic "Opening tables" on MySQL Insert - mysql

Question

I have a long-running insert that shows a status that toggles between "NULL" and "Opening tables"
| 5 | mckelvey | mushroom.jpl.nasa.gov:57050 | smap_ampcs_v5_2_0 | Query | 7105 | Opening tables | INSERT INTO ChannelValue
| 5 | mckelvey | mushroom.jpl.nasa.gov:57050 | smap_ampcs_v5_2_0 | Query | 7114 | NULL | INSERT INTO ChannelValue
It does this continually. Show open tables shows 10 opened tables, 5 in use.
Global status "Opened_tables" is 190 and does not increase. table_open_cache is 1024.
Is something wrong? Why does it constantly open tables for an insert already in progress?
The insert is below. The tables in the v4 database are MyISAM, and v5_2 are InnoDB. ComboParent is temporary and MyISAM. No errors in the server log.
INSERT INTO ChannelValue
SELECT
cv.sessionId,
cv.hostId,
cv.sessionFragment,
1 AS id,
cv.id AS channelDataId,
cp.parentId,
NULL AS uniqueId,
IF (cv.dnUnsignedValue IS NOT NULL,
CONVERT(cv.dnUnsignedValue, SIGNED),
cv.dnIntegerValue) AS dnPackedValue,
cv.dnDoubleValue,
sv.stringId,
cv.eu,
SET_FLAGS(cv.dnDoubleFlag,
cv.euFlag,
cv.dnAlarmState,
cv.euAlarmState,
cv.dnUnsignedValue) AS flags
FROM smap_ampcs_v4_0_0.ChannelValue AS cv
STRAIGHT_JOIN ComboParent AS cp
ON ((cv.sessionId = cp.sessionId) AND
(cv.hostId = cp.hostId) AND
(cv.sessionFragment = cp.sessionFragment) AND
(cv.sclkCoarse = cp.sclkCoarse) AND
(cv.sclkFine = cp.sclkFine) AND
(cv.ertCoarse = cp.ertCoarse) AND
(cv.ertFine = cp.ertFine) AND
(cv.scetCoarse = cp.scetCoarse) AND
(cv.scetFine = cp.scetFine) AND
(cv.dssId = cp.dssId) AND
(cv.vcid <=> cp.vcid) AND
(cv.isRealtime = cp.isRealtime))
LEFT JOIN StringValue AS sv
ON (
(cv.hostId = sv.hostId) AND
(cv.sessionId = sv.sessionId) AND
(cv.sessionFragment = sv.sessionFragment) AND
(0 = sv.fromSse) AND
(cv.dnStringValue = sv.stringValue)
)
WHERE (cv.packetId IS NULL)