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 69e57c68b3a903c135e999a8a73a6f10605ca31e..72b50bae79f23a43aeb760fb1ffa1b3f93d5d785 100644 (file)
--- a/doc/src/sgml/high-availability.sgml
+++ b/doc/src/sgml/high-availability.sgml
@@ -2334,7 +2334,7 @@ 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 d51641079a0e5de269afa2ce457b129c927e91fa..75df5e4947c36e5a35462ed7810e43ebd178c99f 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>