v2-0001-Refactor-pg_resetwal-t-001_basic.pl.patch

From a1bbaddbc00004e97e95ed15b51e48386be5fb4b Mon Sep 17 00:00:00 2001
From: Svetlana Derevyanko <s.derevyanko@postgrespro.ru>
Date: Tue, 26 Mar 2024 13:09:43 +0300
Subject: [PATCH v2] Refactor pg_resetwal/t/001_basic.pl

Use constants instead of magic numbers.
Added MXID_SIZE and MXOFF_SIZE constants.
Changed desciptions for pg_resetwal options in docs.

---
 doc/src/sgml/ref/pg_resetwal.sgml      |  8 ++++----
 src/backend/access/transam/multixact.c | 15 +++++++++------
 src/bin/pg_resetwal/t/001_basic.pl     | 18 +++++++++++++++---
 3 files changed, 28 insertions(+), 13 deletions(-)

diff --git a/doc/src/sgml/ref/pg_resetwal.sgml b/doc/src/sgml/ref/pg_resetwal.sgml
index cf9c7e70f2..d8de5e2e29 100644
--- a/doc/src/sgml/ref/pg_resetwal.sgml
+++ b/doc/src/sgml/ref/pg_resetwal.sgml
@@ -274,7 +274,7 @@ PostgreSQL documentation
       names are in hexadecimal, so the easiest way to do this is to specify
       the option value in hexadecimal and append four zeroes.
      </para>
-     <!-- 65536 = SLRU_PAGES_PER_SEGMENT * BLCKSZ / sizeof(MultiXactOffset) -->
+     <!-- 65536 = SLRU_PAGES_PER_SEGMENT * MULTIXACT_OFFSETS_PER_PAGE -->
     </listitem>
    </varlistentry>
 
@@ -309,7 +309,7 @@ PostgreSQL documentation
       The file names are in hexadecimal.  There is no simple recipe such as
       the ones for other options of appending zeroes.
      </para>
-     <!-- 52352 = SLRU_PAGES_PER_SEGMENT * floor(BLCKSZ/20) * 4; see multixact.c -->
+     <!-- 52352 = SLRU_PAGES_PER_SEGMENT * MULTIXACT_MEMBERS_PER_PAGE; see multixact.c -->
     </listitem>
    </varlistentry>
 
@@ -358,7 +358,7 @@ PostgreSQL documentation
       in <filename>pg_xact</filename>, <literal>-u 0x700000</literal> will work (five
       trailing zeroes provide the proper multiplier).
      </para>
-     <!-- 1048576 = SLRU_PAGES_PER_SEGMENT * BLCKSZ * CLOG_XACTS_PER_BYTE -->
+     <!-- 1048576 = SLRU_PAGES_PER_SEGMENT * CLOG_XACTS_PER_PAGE -->
     </listitem>
    </varlistentry>
 
@@ -380,7 +380,7 @@ PostgreSQL documentation
       in <filename>pg_xact</filename>, <literal>-x 0x1200000</literal> will work (five
       trailing zeroes provide the proper multiplier).
      </para>
-     <!-- 1048576 = SLRU_PAGES_PER_SEGMENT * BLCKSZ * CLOG_XACTS_PER_BYTE -->
+     <!-- 1048576 = SLRU_PAGES_PER_SEGMENT * CLOG_XACTS_PER_PAGE -->
     </listitem>
    </varlistentry>
   </variablelist>
diff --git a/src/backend/access/transam/multixact.c b/src/backend/access/transam/multixact.c
index 83b578dced..6bda000120 100644
--- a/src/backend/access/transam/multixact.c
+++ b/src/backend/access/transam/multixact.c
@@ -104,8 +104,11 @@
  * MultiXactOffsetPagePrecedes).
  */
 
+#define MXOFF_SIZE sizeof(MultiXactOffset)
+#define MXID_SIZE sizeof(MultiXactId)
+
 /* We need four bytes per offset */
-#define MULTIXACT_OFFSETS_PER_PAGE (BLCKSZ / sizeof(MultiXactOffset))
+#define MULTIXACT_OFFSETS_PER_PAGE (BLCKSZ / MXOFF_SIZE)
 
 #define MultiXactIdToOffsetPage(xid) \
 	((xid) / (MultiXactOffset) MULTIXACT_OFFSETS_PER_PAGE)
@@ -1765,7 +1768,7 @@ AtPrepare_MultiXact(void)
 
 	if (MultiXactIdIsValid(myOldestMember))
 		RegisterTwoPhaseRecord(TWOPHASE_RM_MULTIXACT_ID, 0,
-							   &myOldestMember, sizeof(MultiXactId));
+							   &myOldestMember, MXID_SIZE);
 }
 
 /*
@@ -1832,7 +1835,7 @@ multixact_twophase_recover(TransactionId xid, uint16 info,
 	 * Get the oldest member XID from the state file record, and set it in the
 	 * OldestMemberMXactId slot reserved for this prepared transaction.
 	 */
-	Assert(len == sizeof(MultiXactId));
+	Assert(len == MXID_SIZE);
 	oldestMember = *((MultiXactId *) recdata);
 
 	OldestMemberMXactId[dummyProcNumber] = oldestMember;
@@ -1848,7 +1851,7 @@ multixact_twophase_postcommit(TransactionId xid, uint16 info,
 {
 	ProcNumber	dummyProcNumber = TwoPhaseGetDummyProcNumber(xid, true);
 
-	Assert(len == sizeof(MultiXactId));
+	Assert(len == MXID_SIZE);
 
 	OldestMemberMXactId[dummyProcNumber] = InvalidMultiXactId;
 }
@@ -1877,7 +1880,7 @@ MultiXactShmemSize(void)
 	/* We need 2*MaxOldestSlot perBackendXactIds[] entries */
 #define SHARED_MULTIXACT_STATE_SIZE \
 	add_size(offsetof(MultiXactStateData, perBackendXactIds), \
-			 mul_size(sizeof(MultiXactId) * 2, MaxOldestSlot))
+			 mul_size(MXID_SIZE * 2, MaxOldestSlot))
 
 	size = SHARED_MULTIXACT_STATE_SIZE;
 	size = add_size(size, SimpleLruShmemSize(multixact_offset_buffers, 0));
@@ -2146,7 +2149,7 @@ TrimMultiXact(void)
 		offptr = (MultiXactOffset *) MultiXactOffsetCtl->shared->page_buffer[slotno];
 		offptr += entryno;
 
-		MemSet(offptr, 0, BLCKSZ - (entryno * sizeof(MultiXactOffset)));
+		MemSet(offptr, 0, BLCKSZ - (entryno * MXOFF_SIZE));
 
 		MultiXactOffsetCtl->shared->page_dirty[slotno] = true;
 		LWLockRelease(lock);
diff --git a/src/bin/pg_resetwal/t/001_basic.pl b/src/bin/pg_resetwal/t/001_basic.pl
index 9829e48106..19fb6dc6a2 100644
--- a/src/bin/pg_resetwal/t/001_basic.pl
+++ b/src/bin/pg_resetwal/t/001_basic.pl
@@ -205,8 +205,20 @@ push @cmd,
   '-c',
   sprintf("%d,%d", hex($files[0]) == 0 ? 3 : hex($files[0]), hex($files[-1]));
 
+use constant SLRU_PAGES_PER_SEGMENT => 32;
+use constant MXOFF_SIZE => 4;
+use constant MXID_SIZE => 4;
+use constant MULTIXACT_MEMBERS_PER_MEMBERGROUP => 4;
+use constant MULTIXACT_FLAGBYTES_PER_GROUP => 4;
+use constant MULTIXACT_MEMBERGROUP_SIZE => MXID_SIZE * MULTIXACT_MEMBERS_PER_MEMBERGROUP + MULTIXACT_FLAGBYTES_PER_GROUP;
+use constant MULTIXACT_MEMBERGROUPS_PER_PAGE => int($blcksz / MULTIXACT_MEMBERGROUP_SIZE);
+use constant MULTIXACT_MEMBERS_PER_PAGE => MULTIXACT_MEMBERGROUPS_PER_PAGE * MULTIXACT_MEMBERS_PER_MEMBERGROUP;
+use constant MULTIXACT_OFFSETS_PER_PAGE => int($blcksz / MXOFF_SIZE);
+use constant CLOG_XACTS_PER_BYTE => 4;
+use constant CLOG_XACTS_PER_PAGE => $blcksz * CLOG_XACTS_PER_BYTE;
+
 @files = get_slru_files('pg_multixact/offsets');
-$mult = 32 * $blcksz / 4;
+$mult = SLRU_PAGES_PER_SEGMENT * MULTIXACT_OFFSETS_PER_PAGE;
 # -m argument is "new,old"
 push @cmd, '-m',
   sprintf("%d,%d",
@@ -214,11 +226,11 @@ push @cmd, '-m',
 	hex($files[0]) == 0 ? 1 : hex($files[0] * $mult));
 
 @files = get_slru_files('pg_multixact/members');
-$mult = 32 * int($blcksz / 20) * 4;
+$mult = SLRU_PAGES_PER_SEGMENT * MULTIXACT_MEMBERS_PER_PAGE;
 push @cmd, '-O', (hex($files[-1]) + 1) * $mult;
 
 @files = get_slru_files('pg_xact');
-$mult = 32 * $blcksz * 4;
+$mult = SLRU_PAGES_PER_SEGMENT * CLOG_XACTS_PER_PAGE;
 push @cmd,
   '-u', (hex($files[0]) == 0 ? 3 : hex($files[0]) * $mult),
   '-x', ((hex($files[-1]) + 1) * $mult);
-- 
2.34.1