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2 .My name is Alexander Rubin
• Working with MySQL for over 12 years
– Started at MySQL AB, then Sun Microsystems,
– then Oracle (MySQL Consulting)
– Joined Percona 5 years ago
• Working with MongoDB for 3 years
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https://support.pokemongo.nianticlabs.com/hc/en-us/articles/360001518407-Trading-Pokémon
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https://support.pokemongo.nianticlabs.com/hc/en-us/articles/360001518407-Trading-Pokémon
8 .// this is basic design of what Pokemon exchange can look like
session = db.getMongo().startSession()
session.startTransaction()
session.getDatabase("p").player_items.update(
{player_id : 123}, { $inc: { stardust: -1 } } );
session.getDatabase("p").player_items.update(
{player_id : 321}, { $inc: { stardust: -1 } } );
...
session.getDatabase("p").player_pokemons.update(
{player_id : 321},
$push: {pokemon_id: 987});
…
session.commitTransaction()
https://support.pokemongo.nianticlabs.com/hc/en-us/articles/360001518407-Trading-Pokémon
9 .session = db.getMongo().startSession()
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17 .From MongoDB World 2018: Keynote, https://www.slideshare.net/mongodb/mongodb-world-2018-keynote
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foo:PRIMARY> session = db.getMongo().startSession()
session { "id" : UUID("bdd82af7-ab9d-4cd3-9238-f08ee928f31e") }
foo:PRIMARY> session.startTransaction()
foo:PRIMARY> session.getDatabase("percona").test.insert({today : new Date()})
WriteResult({ "nInserted" : 1 })
●
foo:PRIMARY> session = db.getMongo().startSession()
session { "id" : UUID("eb628bfd-425e-450c-a51b-733435474eaa") }
foo:PRIMARY> session.startTransaction()
foo:PRIMARY> session.getDatabase("percona").test.find()
// nothing
20 .●
foo:PRIMARY> session.commitTransaction()
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foo:PRIMARY> session.getDatabase("percona").test.find()
foo:PRIMARY> // nothing
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foo:PRIMARY> db.test.find()
{ "_id" : ObjectId("5b21361252bbe6e5b9a70a4e"), "today" :
ISODate("2018-06-13T15:19:46.645Z") }
{ "_id" : ObjectId("5b21361252bbe6e5b9a70a4f"), "some_value" : "abc" }
21 .●
use percona
db.test.insert({trx : 0})
● Then we create session1 and update trx to change from 0 to 1:
foo:PRIMARY> session = db.getMongo().startSession()
session { "id" : UUID("0b7b8ce0-919a-401a-af01-69fe90876301") }
foo:PRIMARY> session.startTransaction()
foo:PRIMARY> session.getDatabase("percona").test.update({trx : 0}, {trx: 1})
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
22 .●
foo:PRIMARY> session = db.getMongo().startSession()
session { "id" : UUID("b312c662-247c-47c5-b0c9-23d77f4e9f6d") }
foo:PRIMARY> session.startTransaction()
foo:PRIMARY> session.getDatabase("percona").test.update({trx : 0}, {trx: 2})
WriteCommandError({
"errorLabels" : [
"TransientTransactionError"
], MongoDB catches the
"operationTime" : Timestamp(1529675754, 1), conflict and return the
"ok" : 0, error on the insert
"errmsg" : "WriteConflict", (even before the commit)
"code" : 112,
"codeName" : "WriteConflict",
"$clusterTime" : {
"clusterTime" : Timestamp(1529675754, 1),
"signature" : {
"hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="),
"keyId" : NumberLong(0)
}
}
})
23 .●
Session.startTransaction({ writeConcern: { w: <level>} })
// w: 1, majority
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Session.startTransaction({ readConcern: { level: <level>} })
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Session.startTransaction({ readConcern: { level: "snapshot"} })
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