Reduce default value of max_prepared_transactions from 50 to 5. This

saves nearly 700kB in the default shared memory segment size, which seems
worthwhile, and it is a feature that many users won't use anyway.  Per
Heikki's argument, there is no point in a compromise value --- those who
are using 2PC at all will probably want it at least equal to max_connections.
But we can't set it to zero by default without breaking the prepared_xacts
regression test.

diff --git a/doc/src/sgml/runtime.sgml b/doc/src/sgml/runtime.sgml
index b6d85d81bc3290a56b8214b0472d9ec0ea8d9567..1e88e16991212bab972858d167dcf9595cb95d60 100644 (file)
--- a/doc/src/sgml/runtime.sgml
+++ b/doc/src/sgml/runtime.sgml
@@ -1179,7 +1179,7 @@ SET ENABLE_SEQSCAN TO OFF;
         endterm="sql-prepare-transaction-title">).
         Setting this parameter to zero disables the prepared-transaction
         feature.
-        The default is 50.
+        The default is 5.
         This option can only be set at server start.
        </para>
 

diff --git a/src/backend/access/transam/twophase.c b/src/backend/access/transam/twophase.c
index d4fe92e4ebb3e0627b6d96cccfc4e0c3c251f825..7c8ea844cc38137a6606d3c9742bdebab8e4f0cc 100644 (file)
--- a/src/backend/access/transam/twophase.c
+++ b/src/backend/access/transam/twophase.c
@@ -64,7 +64,7 @@
 #define TWOPHASE_DIR "pg_twophase"
 
 /* GUC variable, can't be changed after startup */
-int max_prepared_xacts = 50;
+int max_prepared_xacts = 5;
 
 /*
  * This struct describes one global transaction that is in prepared state

diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 119dc1fc822c09749ad1e226eaeb005eda245edd..a2312e0d046cc71e4f46cdbfc1d88ea0bf0a888b 100644 (file)
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -1203,7 +1203,7 @@ static struct config_int ConfigureNamesInt[] =
                        NULL
                },
                &max_prepared_xacts,
-               50, 0, INT_MAX, NULL, NULL
+               5, 0, INT_MAX, NULL, NULL
        },
 
 #ifdef LOCK_DEBUG

diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index 6049aafe191b9ae03d598c9fb8e7fe43eb237c69..910f0212a87095efc9e86b71b2af5da470720fb6 100644 (file)
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -90,7 +90,7 @@
 
 #shared_buffers = 1000                 # min 16 or max_connections*2, 8KB each
 #temp_buffers = 1000                   # min 100, 8KB each
-#max_prepared_transactions = 50                # can be 0 or more
+#max_prepared_transactions = 5         # can be 0 or more
 #work_mem = 1024                       # min 64, size in KB
 #maintenance_work_mem = 16384          # min 1024, size in KB
 #max_stack_depth = 2048                        # min 100, size in KB