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doc: clarify text around MVCC example query

Reported-by: marlene.brandstaetter@cargonet.software

Discussion: https://postgr.es/m/167765529052.987840.12345375075704447735@wrigleys.postgresql.org

Backpatch-through: master
This commit is contained in:
Bruce Momjian 2024-11-01 16:38:16 -04:00
parent 4a9effe45e
commit 2fa255ce9b

View File

@ -417,8 +417,8 @@
does not see effects of those commands on other rows in the database.
This behavior makes Read Committed mode unsuitable for commands that
involve complex search conditions; however, it is just right for simpler
cases. For example, consider updating bank balances with transactions
like:
cases. For example, consider transferring $100 from one account
to another:
<screen>
BEGIN;
@ -427,8 +427,8 @@ UPDATE accounts SET balance = balance - 100.00 WHERE acctnum = 7534;
COMMIT;
</screen>
If two such transactions concurrently try to change the balance of account
12345, we clearly want the second transaction to start with the updated
If another transactions concurrently tries to change the balance of account
7534, we clearly want the second statement to start with the updated
version of the account's row. Because each command is affecting only a
predetermined row, letting it see the updated version of the row does
not create any troublesome inconsistency.