doc: clarify wording about phantom reads

Reported-by: akhilhello@gmail.com
Discussion: https://postgr.es/m/165222922369.669.10475917322916060899@wrigleys.postgresql.org

Backpatch-through: 10

diff --git a/doc/src/sgml/high-availability.sgml b/doc/src/sgml/high-availability.sgml
index 88c4a797168c912034f28984d21c40efe31490de..b933c58430cc7e6036185c8cc5197af2b6c444b7 100644 (file)
--- a/doc/src/sgml/high-availability.sgml
+++ b/doc/src/sgml/high-availability.sgml
@@ -2326,7 +2326,7 @@ LOG:  database system is ready to accept read only connections
     Currently, temporary table creation is not allowed during read only
     transactions, so in some cases existing scripts will not run correctly.
     This restriction might be relaxed in a later release. This is
-    both a SQL Standard compliance issue and a technical issue.
+    both a SQL standard compliance issue and a technical issue.
    </para>
 
    <para>

diff --git a/doc/src/sgml/mvcc.sgml b/doc/src/sgml/mvcc.sgml
index 40159b8dcd9b70e26c67577de81defda8aa5a3f8..d3ea0b360e215227b80b60503a664419a7ff528c 100644 (file)
--- a/doc/src/sgml/mvcc.sgml
+++ b/doc/src/sgml/mvcc.sgml
@@ -277,9 +277,10 @@
 
    <para>
     The table also shows that PostgreSQL's Repeatable Read implementation
-    does not allow phantom reads.  Stricter behavior is permitted by the
-    SQL standard: the four isolation levels only define which phenomena
-    must not happen, not which phenomena <emphasis>must</emphasis> happen.
+    does not allow phantom reads.  This is acceptable under the SQL
+    standard because the standard specifies which anomalies must
+    <emphasis>not</emphasis> occur at certain isolation levels;  higher
+    guarantees are acceptable.
     The behavior of the available isolation levels is detailed in the
     following subsections.
    </para>