Change CRCs in WAL records from 64bit to 32bit for performance reasons.

Instead of a separate CRC on each backup block, include backup blocks
in their parent WAL record's CRC; this is important to ensure that the
backup block really goes with the WAL record, ie there was not a page
tear right at the start of the backup block.  Implement a simple form
of compression of backup blocks: drop any run of zeroes starting at
pd_lower, so as not to store the unused 'hole' that commonly exists in
PG heap and index pages.  Tweak PageRepairFragmentation and related
routines to ensure they keep the unused space zeroed, so that the above
compression method remains effective.  All per recent discussions.

1 files changed, 105 insertions, 5 deletions

diff --git a/src/backend/utils/hash/pg_crc.c b/src/backend/utils/hash/pg_crc.c
index bf23242a5a..211da1aa72 100644
--- a/src/backend/utils/hash/pg_crc.c
+++ b/src/backend/utils/hash/pg_crc.c
@@ -1,14 +1,25 @@
 /*-------------------------------------------------------------------------
  *
  * pg_crc.c
- *	  PostgreSQL 64-bit CRC support
+ *	  PostgreSQL CRC support
+ *
+ * See Ross Williams' excellent introduction
+ * A PAINLESS GUIDE TO CRC ERROR DETECTION ALGORITHMS, available from
+ * ftp://ftp.rocksoft.com/papers/crc_v3.txt or several other net sites.
+ *
+ * We use a normal (not "reflected", in Williams' terms) CRC, using initial
+ * all-ones register contents and a final bit inversion.
+ *
+ * The 64-bit variant is not used as of PostgreSQL 8.1, but we retain the
+ * code for possible future use.
+ *
  *
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/hash/pg_crc.c,v 1.12 2004/12/31 22:01:37 pgsql Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/hash/pg_crc.c,v 1.13 2005/06/02 05:55:29 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -17,9 +28,96 @@
 #include "utils/pg_crc.h"
 
 
+/*
+ * This table is based on the polynomial
+ *	x^32+x^26+x^23+x^22+x^16+x^12+x^11+x^10+x^8+x^7+x^5+x^4+x^2+x+1.
+ * (This is the same polynomial used in Ethernet checksums, for instance.)
+ */
+const uint32 pg_crc32_table[256] = {
+	0x00000000, 0x77073096, 0xEE0E612C, 0x990951BA,
+	0x076DC419, 0x706AF48F, 0xE963A535, 0x9E6495A3,
+	0x0EDB8832, 0x79DCB8A4, 0xE0D5E91E, 0x97D2D988,
+	0x09B64C2B, 0x7EB17CBD, 0xE7B82D07, 0x90BF1D91,
+	0x1DB71064, 0x6AB020F2, 0xF3B97148, 0x84BE41DE,
+	0x1ADAD47D, 0x6DDDE4EB, 0xF4D4B551, 0x83D385C7,
+	0x136C9856, 0x646BA8C0, 0xFD62F97A, 0x8A65C9EC,
+	0x14015C4F, 0x63066CD9, 0xFA0F3D63, 0x8D080DF5,
+	0x3B6E20C8, 0x4C69105E, 0xD56041E4, 0xA2677172,
+	0x3C03E4D1, 0x4B04D447, 0xD20D85FD, 0xA50AB56B,
+	0x35B5A8FA, 0x42B2986C, 0xDBBBC9D6, 0xACBCF940,
+	0x32D86CE3, 0x45DF5C75, 0xDCD60DCF, 0xABD13D59,
+	0x26D930AC, 0x51DE003A, 0xC8D75180, 0xBFD06116,
+	0x21B4F4B5, 0x56B3C423, 0xCFBA9599, 0xB8BDA50F,
+	0x2802B89E, 0x5F058808, 0xC60CD9B2, 0xB10BE924,
+	0x2F6F7C87, 0x58684C11, 0xC1611DAB, 0xB6662D3D,
+	0x76DC4190, 0x01DB7106, 0x98D220BC, 0xEFD5102A,
+	0x71B18589, 0x06B6B51F, 0x9FBFE4A5, 0xE8B8D433,
+	0x7807C9A2, 0x0F00F934, 0x9609A88E, 0xE10E9818,
+	0x7F6A0DBB, 0x086D3D2D, 0x91646C97, 0xE6635C01,
+	0x6B6B51F4, 0x1C6C6162, 0x856530D8, 0xF262004E,
+	0x6C0695ED, 0x1B01A57B, 0x8208F4C1, 0xF50FC457,
+	0x65B0D9C6, 0x12B7E950, 0x8BBEB8EA, 0xFCB9887C,
+	0x62DD1DDF, 0x15DA2D49, 0x8CD37CF3, 0xFBD44C65,
+	0x4DB26158, 0x3AB551CE, 0xA3BC0074, 0xD4BB30E2,
+	0x4ADFA541, 0x3DD895D7, 0xA4D1C46D, 0xD3D6F4FB,
+	0x4369E96A, 0x346ED9FC, 0xAD678846, 0xDA60B8D0,
+	0x44042D73, 0x33031DE5, 0xAA0A4C5F, 0xDD0D7CC9,
+	0x5005713C, 0x270241AA, 0xBE0B1010, 0xC90C2086,
+	0x5768B525, 0x206F85B3, 0xB966D409, 0xCE61E49F,
+	0x5EDEF90E, 0x29D9C998, 0xB0D09822, 0xC7D7A8B4,
+	0x59B33D17, 0x2EB40D81, 0xB7BD5C3B, 0xC0BA6CAD,
+	0xEDB88320, 0x9ABFB3B6, 0x03B6E20C, 0x74B1D29A,
+	0xEAD54739, 0x9DD277AF, 0x04DB2615, 0x73DC1683,
+	0xE3630B12, 0x94643B84, 0x0D6D6A3E, 0x7A6A5AA8,
+	0xE40ECF0B, 0x9309FF9D, 0x0A00AE27, 0x7D079EB1,
+	0xF00F9344, 0x8708A3D2, 0x1E01F268, 0x6906C2FE,
+	0xF762575D, 0x806567CB, 0x196C3671, 0x6E6B06E7,
+	0xFED41B76, 0x89D32BE0, 0x10DA7A5A, 0x67DD4ACC,
+	0xF9B9DF6F, 0x8EBEEFF9, 0x17B7BE43, 0x60B08ED5,
+	0xD6D6A3E8, 0xA1D1937E, 0x38D8C2C4, 0x4FDFF252,
+	0xD1BB67F1, 0xA6BC5767, 0x3FB506DD, 0x48B2364B,
+	0xD80D2BDA, 0xAF0A1B4C, 0x36034AF6, 0x41047A60,
+	0xDF60EFC3, 0xA867DF55, 0x316E8EEF, 0x4669BE79,
+	0xCB61B38C, 0xBC66831A, 0x256FD2A0, 0x5268E236,
+	0xCC0C7795, 0xBB0B4703, 0x220216B9, 0x5505262F,
+	0xC5BA3BBE, 0xB2BD0B28, 0x2BB45A92, 0x5CB36A04,
+	0xC2D7FFA7, 0xB5D0CF31, 0x2CD99E8B, 0x5BDEAE1D,
+	0x9B64C2B0, 0xEC63F226, 0x756AA39C, 0x026D930A,
+	0x9C0906A9, 0xEB0E363F, 0x72076785, 0x05005713,
+	0x95BF4A82, 0xE2B87A14, 0x7BB12BAE, 0x0CB61B38,
+	0x92D28E9B, 0xE5D5BE0D, 0x7CDCEFB7, 0x0BDBDF21,
+	0x86D3D2D4, 0xF1D4E242, 0x68DDB3F8, 0x1FDA836E,
+	0x81BE16CD, 0xF6B9265B, 0x6FB077E1, 0x18B74777,
+	0x88085AE6, 0xFF0F6A70, 0x66063BCA, 0x11010B5C,
+	0x8F659EFF, 0xF862AE69, 0x616BFFD3, 0x166CCF45,
+	0xA00AE278, 0xD70DD2EE, 0x4E048354, 0x3903B3C2,
+	0xA7672661, 0xD06016F7, 0x4969474D, 0x3E6E77DB,
+	0xAED16A4A, 0xD9D65ADC, 0x40DF0B66, 0x37D83BF0,
+	0xA9BCAE53, 0xDEBB9EC5, 0x47B2CF7F, 0x30B5FFE9,
+	0xBDBDF21C, 0xCABAC28A, 0x53B39330, 0x24B4A3A6,
+	0xBAD03605, 0xCDD70693, 0x54DE5729, 0x23D967BF,
+	0xB3667A2E, 0xC4614AB8, 0x5D681B02, 0x2A6F2B94,
+	0xB40BBE37, 0xC30C8EA1, 0x5A05DF1B, 0x2D02EF8D
+};
+
+
+#ifdef PROVIDE_64BIT_CRC
+
+/*
+ * This table is based on the polynomial
+ *
+ * x^64 + x^62 + x^57 + x^55 + x^54 + x^53 + x^52 + x^47 + x^46 + x^45 +
+ * x^40 + x^39 + x^38 + x^37 + x^35 + x^33 + x^32 + x^31 + x^29 + x^27 +
+ * x^24 + x^23 + x^22 + x^21 + x^19 + x^17 + x^13 + x^12 + x^10 + x^9 +
+ * x^7 + x^4 + x + 1
+ *
+ * which is borrowed from the DLT1 spec
+ * (ECMA-182, available from http://www.ecma.ch/ecma1/STAND/ECMA-182.HTM)
+ */
+
 #ifdef INT64_IS_BUSTED
 
-const uint32 crc_table0[256] = {
+const uint32 pg_crc64_table0[256] = {
 	0x00000000, 0xA9EA3693,
 	0x53D46D26, 0xFA3E5BB5,
 	0x0E42ECDF, 0xA7A8DA4C,
@@ -150,7 +248,7 @@ const uint32 crc_table0[256] = {
 	0x676F8394, 0xCE85B507
 };
 
-const uint32 crc_table1[256] = {
+const uint32 pg_crc64_table1[256] = {
 	0x00000000, 0x42F0E1EB,
 	0x85E1C3D7, 0xC711223C,
 	0x49336645, 0x0BC387AE,
@@ -283,7 +381,7 @@ const uint32 crc_table1[256] = {
 
 #else							/* int64 works */
 
-const uint64 crc_table[256] = {
+const uint64 pg_crc64_table[256] = {
 	UINT64CONST(0x0000000000000000), UINT64CONST(0x42F0E1EBA9EA3693),
 	UINT64CONST(0x85E1C3D753D46D26), UINT64CONST(0xC711223CFA3E5BB5),
 	UINT64CONST(0x493366450E42ECDF), UINT64CONST(0x0BC387AEA7A8DA4C),
@@ -415,3 +513,5 @@ const uint64 crc_table[256] = {
 };
 
 #endif   /* INT64_IS_BUSTED */
+
+#endif	/* PROVIDE_64BIT_CRC */