How to add all combinations of two pairs of key-value to a table?

Question

I have a database of items, as each item has a set of key-value pairs such

place => london
field => engineering

since I frequently need to find items having the same two key-value sets. I created supporting tables by storing designated ids for each key and value.

CREATE TABLE ItemKeyValues
(
ItemID int(11) unsigned,
KeyID mediumint(7) unsigned,
ValueID mediumint(7) unsigned,
PRIMARY KEY (ItemID,KeyID,ValueID)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE utf8_general_ci KEY_BLOCK_SIZE=1

CREATE TABLE Pairs
(
PairID int(11) unsigned NOT NULL AUTO_INCREMENT,
Key1 mediumint(7) unsigned,
Value1 mediumint(7) unsigned,
Key2 mediumint(7) unsigned,
Value2 mediumint(7) unsigned,
UNIQUE INDEX(Key1,Value1,Key2,Value2),
PRIMARY KEY (ItemID,KeyID,ValueID)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE utf8_general_ci KEY_BLOCK_SIZE=1

CREATE TABLE ItemPairs
(
PairID int(11) unsigned NOT NULL,
ItemID int(11) unsigned,
PRIMARY KEY (PairID,ItemID)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE utf8_general_ci KEY_BLOCK_SIZE=1

(I removed indices and FKs for simplicity)

For example, one row of the table Pairs is

PairID    Key1             Value1            Key2              Value2
1         3 (for place)    88 (for London)   10 (for field)    9 (for engineering)

I need to fill the last two tables.

1. How can I INSERT all combinations of Key1,Value1,Key2,Value2 from the table ItemKeyValues (KeyID,ValueID)?
2. How can I UPDATE table ItemPairs from the table ItemPairs?

The performance is of great importance since table ItemKeyValues is over 100M rows (though, this is one-time operation).

Answer 1

INSERT INTO Pairs
SELECT DISTINCT NULL, t1.KeyID, t1.ValueID, t2.KeyID, t2.ValueID
FROM ItemKeyValues t1
JOIN ItemKeyValues t2 USING (ItemID)
WHERE t1.KeyID < t2.KeyID;

INSERT INTO ItemPairs
SELECT t1.PairID, t2.ItemID
FROM Pairs t1
JOIN ItemKeyValues t2 ON t1.Key1 = t2.KeyID 
                     AND t1.Value1 = t2.ValueID
JOIN ItemKeyValues t3 ON t1.Key2 = t3.KeyID 
                     AND t1.Value2 = t3.ValueID 
                     AND t2.ItemID = t3.ItemID;

fiddle

PS. I have simplified your structures by removing indices and options.

PPS. Your DDL scripts pack contains at least 1 error (copypaste misprint?).