Comment and documentation changes. (CVS 331)
FossilOrigin-Name: e8595579a5218aa3f344f967a23ac52ea89daca1
This commit is contained in:
drh
parent
a3cf986fa5
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20
manifest
20
manifest
@ -1,5 +1,5 @@
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C Version\s2.1.7\s(CVS\s454)
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D 2001-12-15T03:05:00
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C Comment\sand\sdocumentation\schanges.\s(CVS\s331)
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D 2001-12-15T14:22:19
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F Makefile.in 352fed589f09dd94347e0bb391d047118ebd6105
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F Makefile.template 0fbf0ee1fe38183d760170a13e91fffec64e73f5
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F README a4c0ba11354ef6ba0776b400d057c59da47a4cc0
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@ -19,8 +19,8 @@ F libtool c56e618713c9510a103bda6b95f3ea3900dcacd6
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F ltmain.sh e9ed72eb1d690f447c13945eaf69e28af531eda1
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F publish.sh cb0f8f7bcb65b8360d0f6668a216a9ac9d5da892
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F src/TODO af7f3cab0228e34149cf98e073aa83d45878e7e6
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F src/btree.c c27474fdafb7036eef17673c7291e54c2116d6ff
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F src/btree.h 0250a0a577a98cc64ddf1582d50c08b8d2451650
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F src/btree.c c3c36b3b5f07c3efdabf76df9ea423086b1ce142
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F src/btree.h 8767bd4ecf841c4999b7aee6876906bd607546e7
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F src/build.c 5127f737837a9d2a8cb4b998dbab505c08b8f06a
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F src/delete.c 5d93a21c1388cfb1359bda01c072f25583a2f4f2
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F src/expr.c 6b25c5bb1e750af2e2217c0134a7aa1fc0b11444
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@ -31,8 +31,8 @@ F src/main.c e5fa4773e6684b81fc0bcd9d9ae4578d56660c0c
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F src/md5.c 52f677bfc590e09f71d07d7e327bd59da738d07c
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F src/os.c 07882cde5c61f26751b8ee76fd84726c1f7e453c
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F src/os.h 00a18e0ae1139a64f1d3ead465ae2b9ff43f3db2
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F src/pager.c f39d99e9339e5fff3fd9852f48d2fc8308933d3b
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F src/pager.h df1fb8a759ab69112ea88b9f14601a7633d0ccc0
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F src/pager.c dde0eb5bf9af0ac0ff8a4429b2bee2aec2194ec9
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F src/pager.h f78d064c780855ff70beacbeba0e2324471b26fe
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F src/parse.y 5295f393f41ea89958287e5738e6c12c7cd67482
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F src/printf.c 300a90554345751f26e1fc0c0333b90a66110a1d
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F src/random.c 2a9cc2c9716d14815fd4c2accf89d87a1143e46b
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@ -108,7 +108,7 @@ F www/changes.tcl 0b921ad20b5dd262e5a9594691b9708a311e5912
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F www/crosscompile.tcl 3622ebbe518927a3854a12de51344673eb2dd060
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F www/download.tcl 1ea61f9d89a2a5a9b2cee36b0d5cf97321bdefe0
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F www/dynload.tcl 02eb8273aa78cfa9070dd4501dca937fb22b466c
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F www/faq.tcl 3c26fb2f2acfc9254f2685e23a34acae2490b44f
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F www/faq.tcl 5c6fba68e238a52b4d9d86b0a63ed2d706fc7f1f
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F www/index.tcl 6d6d847dd3e39e9aa7b0c9b8f3144819ff3f9f51
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F www/lang.tcl 6482d90e40fb5ee004a86cf98f3007312a75444e
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F www/mingw.tcl f1c7c0a7f53387dd9bb4f8c7e8571b7561510ebc
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@ -117,7 +117,7 @@ F www/speed.tcl 83457b2bf6bb430900bd48ca3dd98264d9a916a5
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F www/sqlite.tcl 8b5884354cb615049aed83039f8dfe1552a44279
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F www/tclsqlite.tcl 880ef67cb4f2797b95bf1368fc4e0d8ca0fda956
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F www/vdbe.tcl 2013852c27a02a091d39a766bc87cff329f21218
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P 3a31daf6465b989a2b0790a2d1ba22ff955486a0
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R fe372d30b06d43519de0595e4ea6a38e
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P 0d44465347125c8e7e962ffb67213f9953a9b7ab
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R f9524b24c72db56ae24d23e4dfe8d2a7
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U drh
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Z 1ebde59941b4e5e9dcfe12e6c3caef81
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Z c454c32fd5ff2d794a364b8c8ca2dfec
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@ -1 +1 @@
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0d44465347125c8e7e962ffb67213f9953a9b7ab
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e8595579a5218aa3f344f967a23ac52ea89daca1
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12
src/btree.c
12
src/btree.c
@ -9,7 +9,7 @@
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** May you share freely, never taking more than you give.
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**
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*************************************************************************
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** $Id: btree.c,v 1.44 2001/12/15 02:47:28 drh Exp $
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** $Id: btree.c,v 1.45 2001/12/15 14:22:19 drh Exp $
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**
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** This file implements a external (disk-based) database using BTrees.
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** For a detailed discussion of BTrees, refer to
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@ -251,7 +251,7 @@ struct OverflowPage {
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/*
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** For every page in the database file, an instance of the following structure
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** is stored in memory. The u.aDisk[] array contains the raw bits read from
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** the disk. The rest is auxiliary information that held in memory only. The
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** the disk. The rest is auxiliary information held in memory only. The
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** auxiliary info is only valid for regular database pages - it is not
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** used for overflow pages and pages on the freelist.
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**
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@ -635,7 +635,7 @@ int sqliteBtreeClose(Btree *pBt){
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}
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/*
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** Change the number of pages in the cache.
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** Change the limit on the number of pages allowed the cache.
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*/
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int sqliteBtreeSetCacheSize(Btree *pBt, int mxPage){
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sqlitepager_set_cachesize(pBt->pPager, mxPage);
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@ -806,9 +806,13 @@ int sqliteBtreeRollback(Btree *pBt){
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** If wrFlag==0, then the cursor can only be used for reading.
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** If wrFlag==1, then the cursor can be used for reading or writing.
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** A read/write cursor requires exclusive access to its table. There
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** cannot be two or more cursors open on the same table is any one of
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** cannot be two or more cursors open on the same table if any one of
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** cursors is a read/write cursor. But there can be two or more
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** read-only cursors open on the same table.
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**
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** No checking is done to make sure that page iTable really is the
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** root page of a b-tree. If it is not, then the cursor acquired
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** will not work correctly.
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*/
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int sqliteBtreeCursor(Btree *pBt, int iTable, int wrFlag, BtCursor **ppCur){
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int rc;
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@ -10,9 +10,10 @@
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**
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*************************************************************************
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** This header file defines the interface that the sqlite B-Tree file
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** subsystem.
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** subsystem. See comments in the source code for a detailed description
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** of what each interface routine does.
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**
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** @(#) $Id: btree.h,v 1.17 2001/11/07 14:22:00 drh Exp $
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** @(#) $Id: btree.h,v 1.18 2001/12/15 14:22:19 drh Exp $
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*/
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#ifndef _BTREE_H_
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#define _BTREE_H_
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59
src/pager.c
59
src/pager.c
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** file simultaneously, or one process from reading the database while
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** another is writing.
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**
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** @(#) $Id: pager.c,v 1.33 2001/12/14 15:09:57 drh Exp $
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** @(#) $Id: pager.c,v 1.34 2001/12/15 14:22:19 drh Exp $
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*/
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#include "sqliteInt.h"
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#include "pager.h"
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@ -230,17 +230,6 @@ static void pager_reset(Pager *pPager){
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** a write lock on the database. This routine releases the database
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** write lock and acquires a read lock in its place. The journal file
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** is deleted and closed.
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**
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** We have to release the write lock before acquiring the read lock,
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** so there is a race condition where another process can get the lock
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** while we are not holding it. But, no other process should do this
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** because we are also holding a lock on the journal, and no process
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** should get a write lock on the database without first getting a lock
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** on the journal. So this routine should never fail. But it can fail
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** if another process is not playing by the rules. If it does fail,
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** all in-memory cache pages are invalidated, the PAGER_ERR_LOCK bit
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** is set in pPager->errMask, and this routine returns SQLITE_PROTOCOL.
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** SQLITE_OK is returned on success.
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*/
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static int pager_unwritelock(Pager *pPager){
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int rc;
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@ -273,8 +262,15 @@ static int pager_unwritelock(Pager *pPager){
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** consists of a Pgno and SQLITE_PAGE_SIZE bytes of data. See
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** the PageRecord structure for details.
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**
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** For playback, the pages have to be read from the journal in
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** For playback, the pages are read from the journal in
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** reverse order and put back into the original database file.
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** It used to be required to replay pages in reverse order because
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** there was a possibility of a page appearing in the journal more
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** than once. In that case, the original value of the page was
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** the first entry so it should be reset last. But now, a bitmap
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** is used to record every page that is in the journal. No pages
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** are ever repeated. So we could, in theory, playback the journal
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** in the forward direction and it would still work.
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**
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** If the file opened as the journal file is not a well-formed
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** journal file (as determined by looking at the magic number
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@ -383,9 +379,9 @@ void sqlitepager_set_cachesize(Pager *pPager, int mxPage){
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** the first call to sqlitepager_get() and is only held open until the
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** last page is released using sqlitepager_unref().
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**
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** If zFilename is NULL then a random temporary file is created and used
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** as the file to be cached. The file will be deleted automatically when
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** it is closed.
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** If zFilename is NULL then a randomly-named temporary file is created
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** and used as the file to be cached. The file will be deleted
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** automatically when it is closed.
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*/
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int sqlitepager_open(
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Pager **ppPager, /* Return the Pager structure here */
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@ -573,11 +569,12 @@ int sqlitepager_ref(void *pData){
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**
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** Writing all free dirty pages to the database after the sync is a
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** non-obvious optimization. fsync() is an expensive operation so we
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** want to minimize the number that occur. So after an fsync() is forced
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** and we are free to write dirty pages back to the database, it is best
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** to go ahead and do as much of that as possible to minimize the chance
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** of having to do another fsync() later on. Writing dirty free pages
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** in this way make database operations go up to 10 times faster.
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** want to minimize the number it is called. After an fsync() call,
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** we are free to write dirty pages back to the database. It is best
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** to go ahead and write as many dirty pages as possible to minimize
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** the risk of having to do another fsync() later on. Writing dirty
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** free pages in this way was observed to make database operations go
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** up to 10 times faster.
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*/
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static int syncAllPages(Pager *pPager){
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PgHdr *pPg;
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@ -652,7 +649,7 @@ int sqlitepager_get(Pager *pPager, Pgno pgno, void **ppPage){
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*/
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rc = sqliteOsWriteLock(&pPager->fd);
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if( rc!=SQLITE_OK ){
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rc = sqliteOsReadLock(&pPager->fd);
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rc = sqliteOsUnlock(&pPager->fd);
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assert( rc==SQLITE_OK );
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*ppPage = 0;
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return SQLITE_BUSY;
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@ -912,14 +909,25 @@ int sqlitepager_write(void *pData){
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Pager *pPager = pPg->pPager;
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int rc = SQLITE_OK;
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/* Check for errors
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*/
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if( pPager->errMask ){
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return pager_errcode(pPager);
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}
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if( pPager->readOnly ){
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return SQLITE_PERM;
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}
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/* Mark the page as dirty. If the page has already been written
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** to the journal then we can return right away.
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*/
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pPg->dirty = 1;
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if( pPg->inJournal ){ return SQLITE_OK; }
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/* If we get this far, it means that the page needs to be
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** written to the journal file. First check to see if the
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** journal exists and create it if it does not.
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*/
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assert( pPager->state!=SQLITE_UNLOCK );
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if( pPager->state==SQLITE_READLOCK ){
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assert( pPager->aInJournal==0 );
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@ -956,6 +964,10 @@ int sqlitepager_write(void *pData){
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}
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assert( pPager->state==SQLITE_WRITELOCK );
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assert( pPager->journalOpen );
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/* The journal now exists and we have a write lock on the
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** main database file. Write the current page to the journal.
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*/
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if( pPg->pgno <= pPager->origDbSize ){
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rc = sqliteOsWrite(&pPager->jfd, &pPg->pgno, sizeof(Pgno));
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if( rc==SQLITE_OK ){
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@ -970,6 +982,9 @@ int sqlitepager_write(void *pData){
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pPager->aInJournal[pPg->pgno/8] |= 1<<(pPg->pgno&7);
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pPager->needSync = 1;
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}
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/* Mark the current page as being in the journal and return.
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*/
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pPg->inJournal = 1;
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if( pPager->dbSize<pPg->pgno ){
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pPager->dbSize = pPg->pgno;
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@ -13,7 +13,7 @@
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** subsystem. The page cache subsystem reads and writes a file a page
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** at a time and provides a journal for rollback.
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**
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** @(#) $Id: pager.h,v 1.12 2001/11/10 13:51:09 drh Exp $
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** @(#) $Id: pager.h,v 1.13 2001/12/15 14:22:19 drh Exp $
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*/
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/*
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@ -43,6 +43,10 @@ typedef unsigned int Pgno;
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*/
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typedef struct Pager Pager;
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/*
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** See source code comments for a detailed description of the following
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** routines:
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*/
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int sqlitepager_open(Pager **ppPager,const char *zFilename,int nPage,int nEx);
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void sqlitepager_set_destructor(Pager*, void(*)(void*));
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void sqlitepager_set_cachesize(Pager*, int);
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60
www/faq.tcl
60
www/faq.tcl
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#
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# Run this script to generated a faq.html output file
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#
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set rcsid {$Id: faq.tcl,v 1.3 2001/12/05 00:21:21 drh Exp $}
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set rcsid {$Id: faq.tcl,v 1.4 2001/12/15 14:22:19 drh Exp $}
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puts {<html>
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<head>
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@ -93,29 +93,21 @@ faq {
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}
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faq {
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Why does the second INSERT in the following sequence of commands throw
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a constraint exception?
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<blockquote>
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CREATE TABLE t(s varchar(10) primary key);<br>
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INSERT INTO t VALUES('0');<br>
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INSERT INTO t VALUES('0.0');<br>
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</blockquote>
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Why doesn't SQLite allow me to use '0' and '0.0' as the primary
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key on two different rows of the same table?
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} {
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<p>Because column <b>s</b> is a primary key, all values of <b>s</b> must
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be unique. But SQLite thinks that <b>'0'</b> and <b>'0.0'</b> are the
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<p>Every row much have a unique primary key.
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But SQLite thinks that <b>'0'</b> and <b>'0.0'</b> are the
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same value because they compare equal to one another numerically.
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(See the previous question.) Hence the values are not unique and the
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constraint fails.</p>
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(See the previous question.) Hence the values are not unique.</p>
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<p>You can work around this issue in several ways:</p>
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<p>You can work around this issue in two ways:</p>
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<ol>
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<li><p>Remove the <b>primary key</b> clause from the CREATE TABLE so that
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<b>s</b> can contain more than one entry with the same value.
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If you need an index on the <b>s</b> column then create it separately.
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</p></li>
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<li><p>Prepend a space to the beginning of every <b>s</b> value. The initial
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space will mean that the entries are not pure numerics and hence
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will be compared as strings using <b>strcmp()</b>.</p></li>
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<li><p>Remove the <b>primary key</b> clause from the CREATE TABLE.</p></li>
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<li><p>Prepend a space to the beginning of every value you use for
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the primary key. The initial
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space will mean that the entries are not pure numerics and hence
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will be compared as strings using <b>strcmp()</b>.</p></li>
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</ol>
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}
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@ -234,7 +226,7 @@ ORDER BY name;
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}
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faq {
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Is there any known size limits to SQLite databases.
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Are there any known size limits to SQLite databases.
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} {
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<p>Internally, SQLite can handle databases up to 2^40 bytes (1 terabyte)
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in size. But the backend interface to POSIX and Win32 limits files to
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@ -257,6 +249,32 @@ faq {
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number of columns, etc. Indices are similarly unconstrained.</p>
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}
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faq {
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How do I add or delete columns from an existing table in SQLite.
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} {
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<p>SQLite does not support the "ALTER TABLE" SQL command. If you
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what to change the structure of a table, you have to recreate the
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table. You can save existing data to a temporary table, drop the
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old table, create the new table, then copy the data back in from
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the temporary table.</p>
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<p>For example, suppose you have a table named "t1" with columns
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names "a", "b", and "c" and that you want to delete column "c" from
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this table. The following steps illustrate how this could be done:
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</p>
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<blockquote><pre>
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BEGIN TRANSACTION;
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CREATE TEMPORARY TABLE t1_backup(a,b);
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INSERT INTO t1_backup SELECT a,b FROM t1;
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DROP TABLE t1;
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CREATE TABLE t1(a,b);
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INSERT INTO t1 SELECT a,b FROM t1_backup;
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DROP TABLE t1_backup;
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COMMIT;
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</pre></blockquote>
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}
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# End of questions and answers.
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#############
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Block a user