From: drh <>
Date: Wed, 16 Oct 2024 15:03:12 +0000 (+0000)
Subject: Merge the latest trunk enhancements into the wal2 branch.
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=da6f00cc630d66a08337669f5b8c67864375271e;p=thirdparty%2Fsqlite.git

Merge the latest trunk enhancements into the wal2 branch.

FossilOrigin-Name: 2e96c8bb7aab48f373dae9edabfdc070c9d727e192ced51ab1ce633f3f9a7638
---

da6f00cc630d66a08337669f5b8c67864375271e
diff --cc manifest
index 1fde4e10a9,ff584761e6..19940a9953
--- a/manifest
+++ b/manifest
@@@ -1,11 -1,11 +1,11 @@@
- C Fix\sa\susan\swarning\sin\stest_hexio.c\son\sthis\sbranch.
- D 2024-09-30T17:53:47.829
 -C Add\shas_tclconfig\sto\sthe\stidy\smakefile\starget.
 -D 2024-10-16T14:05:39.591
++C Merge\sthe\slatest\strunk\senhancements\sinto\sthe\swal2\sbranch.
++D 2024-10-16T15:03:12.769
  F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
  F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
  F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
- F Makefile.in 7a0afecbf7249a59c6f3a4270d1f7ffbd736a7db8c1aa89a49549192566e32c0
 -F Makefile.in fac8bdd16e874e06ed635af0671da745467c48ac18746f39b0ed5bea5eb7c3cd
++F Makefile.in edb9d4d1e6a442fca546701a1117345541fbe496d2319dcac13e3544c15fbca0
  F Makefile.linux-gcc f3842a0b1efbfbb74ac0ef60e56b301836d05b4d867d014f714fa750048f1ab6
- F Makefile.msc 20f594d77f988ecacfe713442201e019066caf70274006b4bd8f7e1dae2177e9
 -F Makefile.msc 58b69eda1faad5d475092b8aeffab9156ee4901a82db089b166607f2ec907ee4
++F Makefile.msc 51b23c16484ab33359f7d4e859a77b38df06251e0f1021f082376adae4484d1c
  F README.md c3c0f19532ce28f6297a71870f3c7b424729f0e6d9ab889616d3587dd2332159
  F VERSION 0db40f92c04378404eb45bff93e9e42c148c7e54fd3da99469ed21e22411f5a6
  F aclocal.m4 a5c22d164aff7ed549d53a90fa56d56955281f50
@@@ -22,7 -22,7 +22,7 @@@ F autoconf/README.first 6c4f34fe115ff55
  F autoconf/README.txt 42cfd21d0b19dc7d5d85fb5c405c5f3c6a4c923021c39128f6ba685355d8fd56
  F autoconf/configure.ac ec7fa914c5e74ff212fe879f9bb6918e1234497e05facfb641f30c4d5893b277
  F autoconf/tea/Makefile.in 106a96f2f745d41a0f6193f1de98d7355830b65d45032c18cd7c90295ec24196
- F autoconf/tea/README 3e9a3c060f29a44344ab50aec506f4db903fb873
 -F autoconf/tea/README.txt 94fa2472d3ee4139ab24b364d99a70445d0a25531dac3ce03af2055d581f76b4
++F autoconf/tea/README.txt 94fa2472d3ee4139ab24b364d99a70445d0a25531dac3ce03af2055d581f76b4 w autoconf/tea/README
  F autoconf/tea/aclocal.m4 52c47aac44ce0ddb1f918b6993e8beb8eee88f43
  F autoconf/tea/configure.ac 0deb5d6c49c8119f75f436488219fc043127d72057af5dfba2c9ce096a5734bc
  F autoconf/tea/doc/sqlite3.n e1fe45d4f5286ee3d0ccc877aca2a0def488e9bb
@@@ -604,8 -605,8 +607,8 @@@ F ext/session/test_session.c aa29abdcc9
  F ext/userauth/sqlite3userauth.h 7f3ea8c4686db8e40b0a0e7a8e0b00fac13aa7a3
  F ext/userauth/user-auth.txt ca7e9ee82ca4e1c1744295f8184dd70edfae1992865d26c64303f539eb6c084c
  F ext/userauth/userauth.c 7f00cded7dcaa5d47f54539b290a43d2e59f4b1eb5f447545fa865f002fc80cb
 -F ext/wasm/EXPORTED_FUNCTIONS.fiddle.in 27450c8b8c70875a260aca55435ec927068b34cef801a96205adb81bdcefc65c
 +F ext/wasm/EXPORTED_FUNCTIONS.fiddle 7fb73f7150ab79d83bb45a67d257553c905c78cd3d693101699243f36c5ae6c3
- F ext/wasm/GNUmakefile 6b94c3125c40932e71bbe46e582d24ed4c829b9fa2ff34dd842b0ed8a948ac6a
+ F ext/wasm/GNUmakefile bfd63f0462ac7e5b814a267e9101b8284d61731574ec673dae3178643cdb89ef
  F ext/wasm/README-dist.txt 6382cb9548076fca472fb3330bbdba3a55c1ea0b180ff9253f084f07ff383576
  F ext/wasm/README.md a8a2962c3aebdf8d2104a9102e336c5554e78fc6072746e5daf9c61514e7d193
  F ext/wasm/SQLTester/GNUmakefile e0794f676d55819951bbfae45cc5e8d7818dc460492dc317ce7f0d2eca15caff
@@@ -689,7 -690,7 +692,7 @@@ F ext/wasm/wasmfs.make bc8bb227f35d5bd3
  F install-sh 9d4de14ab9fb0facae2f48780b874848cbf2f895 x
  F ltmain.sh 3ff0879076df340d2e23ae905484d8c15d5fdea8
  F magic.txt 5ade0bc977aa135e79e3faaea894d5671b26107cc91e70783aa7dc83f22f3ba0
- F main.mk 31c11018fd9debe1a767a9b32f30a0c5aad8d47a321b7a60dd048f98942f8d02
 -F main.mk c6501abe2d915ed1a2ec3d074e652c096177f93c50ac91f815c831e3417f9019
++F main.mk 8cb748d4e172d081d72650c08d58444ad7b26b7810f629c70ab29d66e0501426
  F mptest/config01.test 3c6adcbc50b991866855f1977ff172eb6d901271
  F mptest/config02.test 4415dfe36c48785f751e16e32c20b077c28ae504
  F mptest/crash01.test 61e61469e257df0850df4293d7d4d6c2af301421
@@@ -714,16 -715,16 +717,16 @@@ F src/btreeInt.h 98aadb6dcb77b012cab257
  F src/build.c 3a1840d9d171ce2d24f4c1f7acda7266ab796c664290c1acba65ff98ce2bd01e
  F src/callback.c db3a45e376deff6a16c0058163fe0ae2b73a2945f3f408ca32cf74960b28d490
  F src/complete.c a3634ab1e687055cd002e11b8f43eb75c17da23e
 -F src/ctime.c b224d3db0f28c4a5f1407c50107a0a8133bd244ff3c7f6f8cedeb896a8cf1b64
 +F src/ctime.c 193f6f9a75204274b7e7f45ac6d6517c12c70b55a5dfb39312dfc3a52e2a8138
  F src/date.c 89ce1ff20512a7fa5070ba6e7dd5c171148ca7d580955795bf97c79c2456144a
- F src/dbpage.c 12e49515d67d4a59625d71f9aa42499556cfdc2e4f1ea49086e674a7f47f46e5
+ F src/dbpage.c db1be8adaf1f839ad733c08baeac5c22aa912f7b535865c0c061382602081360
  F src/dbstat.c 73362c0df0f40ad5523a6f5501224959d0976757b511299bf892313e79d14f5c
  F src/delete.c 03a77ba20e54f0f42ebd8eddf15411ed6bdb06a2c472ac4b6b336521bf7cea42
- F src/expr.c 6d5f2c38fe3ec06a7eac599dac822788b36064124e20112a844e9cd5156cb239
+ F src/expr.c a9d9f5fdfbdd3b2c94d7af1b11f181464b8a641736cf32cb92fa3c5e7ecb30df
  F src/fault.c 460f3e55994363812d9d60844b2a6de88826e007
  F src/fkey.c 928ed2517e8732113d2b9821aa37af639688d752f4ea9ac6e0e393d713eeb76f
- F src/func.c df400a1d3f4625997d4dd8a81951c303e066277c29b861d37e03cd152d7858dd
- F src/global.c 61a419dd9e993b9be0f91de4c4ccf322b053eb829868e089f0321dd669be3b90
+ F src/func.c 1d093b93b8f097665721e59a1c404d7db4dc591e1a777a7a1022dfbda21e108b
+ F src/global.c a19e4b1ca1335f560e9560e590fc13081e21f670643367f99cb9e8f9dc7d615b
  F src/hash.c 9ee4269fb1d6632a6fecfb9479c93a1f29271bddbbaf215dd60420bcb80c7220
  F src/hash.h 3340ab6e1d13e725571d7cee6d3e3135f0779a7d8e76a9ce0a85971fa3953c51
  F src/hwtime.h f9c2dfb84dce7acf95ce6d289e46f5f9d3d1afd328e53da8f8e9008e3b3caae6
@@@ -753,16 -754,16 +756,16 @@@ F src/os.h 1ff5ae51d339d0e30d8a9d814f4b
  F src/os_common.h 6c0eb8dd40ef3e12fe585a13e709710267a258e2c8dd1c40b1948a1d14582e06
  F src/os_kv.c 4d39e1f1c180b11162c6dc4aa8ad34053873a639bac6baae23272fc03349986a
  F src/os_setup.h 6011ad7af5db4e05155f385eb3a9b4470688de6f65d6166b8956e58a3d872107
- F src/os_unix.c 779e83666ecd535f6725497ba6da069c1d15138ff6a4ee123edad1ae0cdfbe83
+ F src/os_unix.c 14d0f80e4779f5f76bcc71e7af97e3efe318fa3d0b22335623c59fab7d39302b
  F src/os_win.c 6ff43bac175bd9ed79e7c0f96840b139f2f51d01689a638fd05128becf94908a
  F src/os_win.h 7b073010f1451abe501be30d12f6bc599824944a
 -F src/pager.c b08600ebf0db90b6d1e9b8b6577c6fa3877cbe1a100bd0b2899e4c6e9adad4b3
 -F src/pager.h 4b1140d691860de0be1347474c51fee07d5420bd7f802d38cbab8ea4ab9f538a
 +F src/pager.c d2f77fe2133a3c33ee5552bde00efec2afae790a75e7903aeff3bdb193f30a8a
 +F src/pager.h fc0c95d27f2aefffcb39b4373b3557e89e1b4b9a36b183cc04d6f22002bf0ad2
  F src/parse.y a7a8d42eeff01d267444ddb476029b0b1726fb70ae3d77984140f17ad02e2d61
  F src/pcache.c 588cc3c5ccaaadde689ed35ce5c5c891a1f7b1f4d1f56f6cf0143b74d8ee6484
  F src/pcache.h 1497ce1b823cf00094bb0cf3bac37b345937e6f910890c626b16512316d3abf5
  F src/pcache1.c 49516ad7718a3626f28f710fa7448ef1fce3c07fd169acbb4817341950264319
- F src/pragma.c d206a9a757faceb812183faa2ed328145795c8067a44f981b0478736f68d4144
 -F src/pragma.c cd613126f7cdd0c2ded4648c3c7b7b0239e678d7f3489e88c4b6d6858372fd07
++F src/pragma.c 92daeda7cadb4d96564f9326a6558e1eb73b81afab584e188b7b8b9463de5cec
  F src/pragma.h e690a356c18e98414d2e870ea791c1be1545a714ba623719deb63f7f226d8bb7
  F src/prepare.c 3ba0ad907b7773ed642f66cea8a2c9c8edc18841aa1050b6218dbb3479e86225
  F src/printf.c 6a87534ebfb9e5346011191b1f3a7ebc457f5938c7e4feeea478ecf53f6a41b2
@@@ -836,14 -837,14 +839,14 @@@ F src/treeview.c 88aa39b754f5ef7214385c
  F src/trigger.c 0bb986a5b96047fd597c6aac28588853df56064e576e6b81ba777ef2ccaac461
  F src/update.c 0e01aa6a3edf9ec112b33eb714b9016a81241497b1fb7c3e74332f4f71756508
  F src/upsert.c 215328c3f91623c520ec8672c44323553f12caeb4f01b1090ebdca99fdf7b4f1
- F src/utf.c 7bc550af6f3ddd5f5dc82d092c41f728acb760c92e0b47f391963b01ae52569b
- F src/util.c 5d1a0134cf4240648d1c6bb5cc8efaca0ea2b5d5c840985aec7e947271f04375
+ F src/utf.c 8b29d9a5956569ea2700f869669b8ef67a9662ee5e724ff77ab3c387e27094ba
+ F src/util.c 4d57ae861d0e234019be9596818228d7715e44e6efaccb612cf4498bedc2e023
  F src/vacuum.c b763b6457bd058d2072ef9364832351fd8d11e8abf70cbb349657360f7d55c40
 -F src/vdbe.c be5f58bc29f60252e041a618eae59e8d57d460ba136c5403cf0abf955560c457
 +F src/vdbe.c f2e6668400689ed448c6865fc5748fcbbdc1ed0861e3773d10c69ffd7001d742
  F src/vdbe.h c2549a215898a390de6669cfa32adba56f0d7e17ba5a7f7b14506d6fd5f0c36a
  F src/vdbeInt.h af7d7e8291edd0b19f2cd698e60e4d4031078f9a2f2328ac8f0b7efb134f8a1d
  F src/vdbeapi.c 53c7e26a2c0821a892b20eee2cde4656e31998212f3d515576c780dfaa45fd17
- F src/vdbeaux.c 3b2bd3264442f38d05b6180acccaaf0de55e34177e6e38d5ed2abb52e4584784
 -F src/vdbeaux.c f06f011e4fac948941ea821ac365a9f1c163ef473e63756d6e499a37c6bda9ef
++F src/vdbeaux.c 7a87d215ea1814160634748ebebd919c921984e60ddef91fc3161480ff623ddc
  F src/vdbeblob.c 255be187436da38b01f276c02e6a08103489bbe2a7c6c21537b7aecbe0e1f797
  F src/vdbemem.c df568ef0187e4be2788c35174f6d9b8566ab9475f9aff2d73907ed05aa5684b2
  F src/vdbesort.c d0a3c7056c081703c8b6d91ad60f17da5e062a5c64bf568ed0fa1b5f4cae311f
@@@ -851,13 -852,13 +854,13 @@@ F src/vdbetrace.c fe0bc29ebd4e02c8bc5c1
  F src/vdbevtab.c fc46b9cbd759dc013f0b3724549cc0d71379183c667df3a5988f7e2f1bd485f3
  F src/vtab.c 316cd48e9320660db3047cd306cd056e4361180cebb4d0f10a39244e10c11422
  F src/vxworks.h d2988f4e5a61a4dfe82c6524dd3d6e4f2ce3cdb9
- F src/wal.c 83d1d292547df87573278731973be245797e28fbae4154bfb7cd1471cf48a6ee
 -F src/wal.c a0d42bfdef935e1389737152394d08e59e7c48697f40a9fc2e0552cb19dc731f
 -F src/wal.h ba252daaa94f889f4b2c17c027e823d9be47ce39da1d3799886bbd51f0490452
++F src/wal.c bb476dcec9baa4b19118a7ec393a2005583be79029fcf58b10eb46f63b5e7540
 +F src/wal.h 97b8a9903387401377b59507e86b93a148ef1ad4e5ce0f23659a12dcdce56af2
  F src/walker.c d5006d6b005e4ea7302ad390957a8d41ed83faa177e412f89bc5600a7462a014
- F src/where.c 461d41017d900d4248a268df96d2d30506c4dcc2257f4167c4f46072003ce2cf
+ F src/where.c 12fe24880901997372b88fd7ca9a21457404ad35201712c02cc57978578abb10
  F src/whereInt.h a5d079c346a658b7a6e9e47bb943d021e02fa1e6aed3b964ca112112a4892192
  F src/wherecode.c 5172d647798134e7c92536ddffe7e530c393d79b5dedd648b88faf2646c65baf
- F src/whereexpr.c 44f41ae554c7572e1de1485b3169b233ee04d464b2ee5881687ede3bf07cacfa
+ F src/whereexpr.c 0f93a29cabd3a338d09a1f5c6770620a1ac51ec1157f3229502a7e7767c60b6f
  F src/window.c 499d48f315a09242dc68f2fac635ed27dcf6bbb0d9ab9084857898c64489e975
  F test/8_3_names.test ebbb5cd36741350040fd28b432ceadf495be25b2
  F test/affinity2.test ce1aafc86e110685b324e9a763eab4f2a73f737842ec3b687bd965867de90627
@@@ -1716,9 -1718,9 +1720,9 @@@ F test/temptable.test d2c9b87a54147161b
  F test/temptable2.test 76821347810ecc88203e6ef0dd6897b6036ac788e9dd3e6b04fd4d1631311a16
  F test/temptable3.test d11a0974e52b347e45ee54ef1923c91ed91e4637
  F test/temptrigger.test 38f0ca479b1822d3117069e014daabcaacefffcc
 -F test/tester.tcl 7b44f1a9b9a2de8112695b908afc21dd9a68cd2d44e84b73f1b27b53492c0d59
 +F test/tester.tcl b1ffedf6bc6e0044448813e37f3ec3496e35268c35802a508f2f013cf5f74247
  F test/testrunner.tcl 3dd75b45593d2afa2e3bca76121297a9f163bebb98474b13536f326829a71db1 x
- F test/testrunner_data.tcl dbc0bb1c5b912dfd1e32b25d544318e412edd6085bd5fc9e6619cb93a739b786
+ F test/testrunner_data.tcl c7b3b911e44f7e8c01cc6bc7571e16115cdc2e4db46630bd2acd7a931a46380e
  F test/thread001.test a0985c117eab62c0c65526e9fa5d1360dd1cac5b03bde223902763274ce21899
  F test/thread002.test c24c83408e35ba5a952a3638b7ac03ccdf1ce4409289c54a050ac4c5f1de7502
  F test/thread003.test ee4c9efc3b86a6a2767516a37bd64251272560a7
@@@ -2188,11 -2178,11 +2192,11 @@@ F tool/speedtest8inst1.c 7ce07da76b5e74
  F tool/spellsift.tcl 52b4b04dc4333c7ab024f09d9d66ed6b6f7c6eb00b38497a09f338fa55d40618 x
  F tool/split-sqlite3c.tcl 5aa60643afca558bc732b1444ae81a522326f91e1dc5665b369c54f09e20de60
  F tool/sqldiff.c 2a0987d183027c795ced13d6749061c1d2f38e24eddb428f56fa64c3a8f51e4b
- F tool/sqlite3-rsync.c 187b262035c1159b047dbfa1959c168b87b5a153b63465e8c8bd1b54fabf4460
  F tool/sqlite3_analyzer.c.in 348ba349bbdc93c9866439f9f935d7284866a2a4e6898bc906ae1204ade56918
 -F tool/sqlite3_rsync.c 2a2b79a0463d400696aa9429be5c0ddec6b1f7ceefa5fed7acfdc859a435221f
++F tool/sqlite3_rsync.c 2a2b79a0463d400696aa9429be5c0ddec6b1f7ceefa5fed7acfdc859a435221f w tool/sqlite3-rsync.c
  F tool/sqltclsh.c.in 1bcc2e9da58fadf17b0bf6a50e68c1159e602ce057210b655d50bad5aaaef898
  F tool/sqltclsh.tcl 862f4cf1418df5e1315b5db3b5ebe88969e2a784525af5fbf9596592f14ed848
- F tool/src-verify.c 41c586dee84d0b190ad13e0282ed83d4a65ec9fefde9adf4943efdf6558eea7f
+ F tool/src-verify.c d00f93263aa2fa6ba0cba0106d95458e6effb94fdb5fc634f56834f90c05bbb4
  F tool/srcck1.c 371de5363b70154012955544f86fdee8f6e5326f
  F tool/srctree-check.tcl c15f860a3c97d5f7b4c14b60392d9466af29dd006c4ef18127f502641e2977a8
  F tool/stack_usage.tcl f8e71b92cdb099a147dad572375595eae55eca43
@@@ -2227,8 -2217,8 +2231,8 @@@ F vsixtest/vsixtest.tcl 6195aba1f12a5e1
  F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
  F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
  F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
- P ab6356181274016571124989bc10e16256666567bb284612a0a689cf18a50adb
- R b05282f64f82f52e60568844e5597fe7
- U dan
- Z 7723f16e0d8ec4b8fecc8e3015d59289
 -P 86e794cbaa5ae600635c933b46298a39f2465daf4c5cd1570f2a03e19ac08d9d
 -R 6d7f362ce02ddb09816fb4a964c469dc
 -U stephan
 -Z cd1d3303e56f0d3e84aeead9caca08c6
++P 59fba0288d8fb68f9b6e4936c09ae9169bc002bfe6548354504563a674000c20 309e6d6f07d4169fbd6ea1d8b3d4809186ad9b7a2e69bbd33eedb9a55e831d68
++R 1bda8bee6dbcdca1292e34845f00228f
++U drh
++Z d8af42625b43acc1020d428bf990ef75
  # Remove this line to create a well-formed Fossil manifest.
diff --cc manifest.uuid
index 91c0e60e6f,7e839ca5a8..cc607bbae4
--- a/manifest.uuid
+++ b/manifest.uuid
@@@ -1,1 -1,1 +1,1 @@@
- 59fba0288d8fb68f9b6e4936c09ae9169bc002bfe6548354504563a674000c20
 -309e6d6f07d4169fbd6ea1d8b3d4809186ad9b7a2e69bbd33eedb9a55e831d68
++2e96c8bb7aab48f373dae9edabfdc070c9d727e192ced51ab1ce633f3f9a7638
diff --cc src/wal.c
index ad5e3965a3,f4aa663fd3..59be868f94
--- a/src/wal.c
+++ b/src/wal.c
@@@ -802,9 -541,8 +802,10 @@@ struct Wal 
  #endif
  #ifdef SQLITE_ENABLE_SNAPSHOT
    WalIndexHdr *pSnapshot;    /* Start transaction here if not NULL */
+   int bGetSnapshot;          /* Transaction opened for sqlite3_get_snapshot() */
  #endif
 +  int bClosing;              /* Set to true at start of sqlite3WalClose() */
 +  int bWal2;                 /* bWal2 flag passed to WalOpen() */
  #ifdef SQLITE_ENABLE_SETLK_TIMEOUT
    sqlite3 *db;
  #endif
@@@ -3718,175 -3096,141 +3719,175 @@@ static int walTryBeginRead(Wal *pWal, i
    assert( pWal->apWiData[0]!=0 );
    pInfo = walCkptInfo(pWal);
    SEH_INJECT_FAULT;
 -  if( !useWal && AtomicLoad(&pInfo->nBackfill)==pWal->hdr.mxFrame
 -#ifdef SQLITE_ENABLE_SNAPSHOT
 -   && ((pWal->bGetSnapshot==0 && pWal->pSnapshot==0) || pWal->hdr.mxFrame==0)
 -#endif
 -  ){
 -    /* The WAL has been completely backfilled (or it is empty).
 -    ** and can be safely ignored.
 -    */
 -    rc = walLockShared(pWal, WAL_READ_LOCK(0));
 +  if( isWalMode2(pWal) ){
 +    /* This connection needs a "part" lock on the current wal file and, 
 +    ** unless pInfo->nBackfill is set to indicate that it has already been
 +    ** checkpointed, a "full" lock on the other wal file.  */
 +    int iWal = walidxGetFile(&pWal->hdr);
 +    int nBackfill = pInfo->nBackfill || walidxGetMxFrame(&pWal->hdr, !iWal)==0;
 +    int eLock = 1 + (iWal*2) + (nBackfill==iWal);
 +
 +    assert( nBackfill==0 || nBackfill==1 );
 +    assert( iWal==0 || iWal==1 );
 +    assert( iWal!=0 || nBackfill!=1 || eLock==WAL_LOCK_PART1 );
 +    assert( iWal!=0 || nBackfill!=0 || eLock==WAL_LOCK_PART1_FULL2 );
 +    assert( iWal!=1 || nBackfill!=1 || eLock==WAL_LOCK_PART2 );
 +    assert( iWal!=1 || nBackfill!=0 || eLock==WAL_LOCK_PART2_FULL1 );
 +
 +    rc = walLockShared(pWal, WAL_READ_LOCK(eLock));
 +    if( rc!=SQLITE_OK ){
 +      return (rc==SQLITE_BUSY ? WAL_RETRY : rc);
 +    }
      walShmBarrier(pWal);
 -    if( rc==SQLITE_OK ){
 -      if( memcmp((void *)walIndexHdr(pWal), &pWal->hdr, sizeof(WalIndexHdr)) ){
 -        /* It is not safe to allow the reader to continue here if frames
 -        ** may have been appended to the log before READ_LOCK(0) was obtained.
 -        ** When holding READ_LOCK(0), the reader ignores the entire log file,
 -        ** which implies that the database file contains a trustworthy
 -        ** snapshot. Since holding READ_LOCK(0) prevents a checkpoint from
 -        ** happening, this is usually correct.
 -        **
 -        ** However, if frames have been appended to the log (or if the log
 -        ** is wrapped and written for that matter) before the READ_LOCK(0)
 -        ** is obtained, that is not necessarily true. A checkpointer may
 -        ** have started to backfill the appended frames but crashed before
 -        ** it finished. Leaving a corrupt image in the database file.
 -        */
 -        walUnlockShared(pWal, WAL_READ_LOCK(0));
 -        return WAL_RETRY;
 +    if( memcmp((void *)walIndexHdr(pWal), &pWal->hdr, sizeof(WalIndexHdr)) ){
 +      walUnlockShared(pWal, WAL_READ_LOCK(eLock));
 +      return WAL_RETRY;
 +    }else{
 +      pWal->readLock = eLock;
 +    }
 +    assert( pWal->minFrame==0 && walFramePage(pWal->minFrame)==0 );
 +  }else{
 +    u32 mxReadMark;               /* Largest aReadMark[] value */
 +    int mxI;                      /* Index of largest aReadMark[] value */
 +    int i;                        /* Loop counter */
 +    u32 mxFrame;                  /* Wal frame to lock to */
 +    if( !useWal && pInfo->nBackfill==pWal->hdr.mxFrame
 +  #ifdef SQLITE_ENABLE_SNAPSHOT
-      && (pWal->pSnapshot==0 || pWal->hdr.mxFrame==0)
++     && ((pWal->bGetSnapshot==0 && pWal->pSnapshot==0) || pWal->hdr.mxFrame==0)
 +  #endif
 +    ){
 +      /* The WAL has been completely backfilled (or it is empty).
 +      ** and can be safely ignored.
 +      */
 +      rc = walLockShared(pWal, WAL_READ_LOCK(0));
 +      walShmBarrier(pWal);
 +      if( rc==SQLITE_OK ){
 +        if( memcmp((void *)walIndexHdr(pWal), &pWal->hdr,sizeof(WalIndexHdr)) ){
 +          /* It is not safe to allow the reader to continue here if frames
 +          ** may have been appended to the log before READ_LOCK(0) was obtained.
 +          ** When holding READ_LOCK(0), the reader ignores the entire log file,
 +          ** which implies that the database file contains a trustworthy
 +          ** snapshot. Since holding READ_LOCK(0) prevents a checkpoint from
 +          ** happening, this is usually correct.
 +          **
 +          ** However, if frames have been appended to the log (or if the log 
 +          ** is wrapped and written for that matter) before the READ_LOCK(0)
 +          ** is obtained, that is not necessarily true. A checkpointer may
 +          ** have started to backfill the appended frames but crashed before
 +          ** it finished. Leaving a corrupt image in the database file.
 +          */
 +          walUnlockShared(pWal, WAL_READ_LOCK(0));
 +          return WAL_RETRY;
 +        }
 +        pWal->readLock = 0;
 +        return SQLITE_OK;
 +      }else if( rc!=SQLITE_BUSY ){
 +        return rc;
        }
 -      pWal->readLock = 0;
 -      return SQLITE_OK;
 -    }else if( rc!=SQLITE_BUSY ){
 -      return rc;
      }
 -  }
 -
 -  /* If we get this far, it means that the reader will want to use
 -  ** the WAL to get at content from recent commits.  The job now is
 -  ** to select one of the aReadMark[] entries that is closest to
 -  ** but not exceeding pWal->hdr.mxFrame and lock that entry.
 -  */
 -  mxReadMark = 0;
 -  mxI = 0;
 -  mxFrame = pWal->hdr.mxFrame;
 -#ifdef SQLITE_ENABLE_SNAPSHOT
 -  if( pWal->pSnapshot && pWal->pSnapshot->mxFrame<mxFrame ){
 -    mxFrame = pWal->pSnapshot->mxFrame;
 -  }
 -#endif
 -  for(i=1; i<WAL_NREADER; i++){
 -    u32 thisMark = AtomicLoad(pInfo->aReadMark+i); SEH_INJECT_FAULT;
 -    if( mxReadMark<=thisMark && thisMark<=mxFrame ){
 -      assert( thisMark!=READMARK_NOT_USED );
 -      mxReadMark = thisMark;
 -      mxI = i;
 +  
 +    /* If we get this far, it means that the reader will want to use
 +    ** the WAL to get at content from recent commits.  The job now is
 +    ** to select one of the aReadMark[] entries that is closest to
 +    ** but not exceeding pWal->hdr.mxFrame and lock that entry.
 +    */
 +    mxReadMark = 0;
 +    mxI = 0;
 +    mxFrame = pWal->hdr.mxFrame;
 +  #ifdef SQLITE_ENABLE_SNAPSHOT
 +    if( pWal->pSnapshot && pWal->pSnapshot->mxFrame<mxFrame ){
 +      mxFrame = pWal->pSnapshot->mxFrame;
      }
 -  }
 -  if( (pWal->readOnly & WAL_SHM_RDONLY)==0
 -   && (mxReadMark<mxFrame || mxI==0)
 -  ){
 +  #endif
      for(i=1; i<WAL_NREADER; i++){
 -      rc = walLockExclusive(pWal, WAL_READ_LOCK(i), 1);
 -      if( rc==SQLITE_OK ){
 -        AtomicStore(pInfo->aReadMark+i,mxFrame);
 -        mxReadMark = mxFrame;
 +      u32 thisMark = AtomicLoad(pInfo->aReadMark+i); SEH_INJECT_FAULT;
 +      if( mxReadMark<=thisMark && thisMark<=mxFrame ){
 +        assert( thisMark!=READMARK_NOT_USED );
 +        mxReadMark = thisMark;
          mxI = i;
 -        walUnlockExclusive(pWal, WAL_READ_LOCK(i), 1);
 -        break;
 -      }else if( rc!=SQLITE_BUSY ){
 -        return rc;
        }
      }
 -  }
 -  if( mxI==0 ){
 -    assert( rc==SQLITE_BUSY || (pWal->readOnly & WAL_SHM_RDONLY)!=0 );
 -    return rc==SQLITE_BUSY ? WAL_RETRY : SQLITE_READONLY_CANTINIT;
 -  }
 -
 -  (void)walEnableBlockingMs(pWal, nBlockTmout);
 -  rc = walLockShared(pWal, WAL_READ_LOCK(mxI));
 -  walDisableBlocking(pWal);
 -  if( rc ){
 -#ifdef SQLITE_ENABLE_SETLK_TIMEOUT
 -    if( rc==SQLITE_BUSY_TIMEOUT ){
 -      *pCnt |= WAL_RETRY_BLOCKED_MASK;
 +    if( (pWal->readOnly & WAL_SHM_RDONLY)==0
 +     && (mxReadMark<mxFrame || mxI==0)
 +    ){
 +      for(i=1; i<WAL_NREADER; i++){
 +        rc = walLockExclusive(pWal, WAL_READ_LOCK(i), 1);
 +        if( rc==SQLITE_OK ){
 +          AtomicStore(pInfo->aReadMark+i,mxFrame);
 +          mxReadMark = mxFrame;
 +          mxI = i;
 +          walUnlockExclusive(pWal, WAL_READ_LOCK(i), 1);
 +          break;
 +        }else if( rc!=SQLITE_BUSY ){
 +          return rc;
 +        }
 +      }
 +    }
 +    if( mxI==0 ){
 +      assert( rc==SQLITE_BUSY || (pWal->readOnly & WAL_SHM_RDONLY)!=0 );
 +      return rc==SQLITE_BUSY ? WAL_RETRY : SQLITE_READONLY_CANTINIT;
      }
 +  
 +    (void)walEnableBlockingMs(pWal, nBlockTmout);
 +    rc = walLockShared(pWal, WAL_READ_LOCK(mxI));
 +    walDisableBlocking(pWal);
 +    if( rc ){
 +#ifdef SQLITE_ENABLE_SETLK_TIMEOUT
 +      if( rc==SQLITE_BUSY_TIMEOUT ){
 +        *pCnt |= WAL_RETRY_BLOCKED_MASK;
 +      }
  #else
 -    assert( rc!=SQLITE_BUSY_TIMEOUT );
 +      assert( rc!=SQLITE_BUSY_TIMEOUT );
  #endif
 -    assert( (rc&0xFF)!=SQLITE_BUSY||rc==SQLITE_BUSY||rc==SQLITE_BUSY_TIMEOUT );
 -    return (rc&0xFF)==SQLITE_BUSY ? WAL_RETRY : rc;
 -  }
 -  /* Now that the read-lock has been obtained, check that neither the
 -  ** value in the aReadMark[] array or the contents of the wal-index
 -  ** header have changed.
 -  **
 -  ** It is necessary to check that the wal-index header did not change
 -  ** between the time it was read and when the shared-lock was obtained
 -  ** on WAL_READ_LOCK(mxI) was obtained to account for the possibility
 -  ** that the log file may have been wrapped by a writer, or that frames
 -  ** that occur later in the log than pWal->hdr.mxFrame may have been
 -  ** copied into the database by a checkpointer. If either of these things
 -  ** happened, then reading the database with the current value of
 -  ** pWal->hdr.mxFrame risks reading a corrupted snapshot. So, retry
 -  ** instead.
 -  **
 -  ** Before checking that the live wal-index header has not changed
 -  ** since it was read, set Wal.minFrame to the first frame in the wal
 -  ** file that has not yet been checkpointed. This client will not need
 -  ** to read any frames earlier than minFrame from the wal file - they
 -  ** can be safely read directly from the database file.
 -  **
 -  ** Because a ShmBarrier() call is made between taking the copy of
 -  ** nBackfill and checking that the wal-header in shared-memory still
 -  ** matches the one cached in pWal->hdr, it is guaranteed that the
 -  ** checkpointer that set nBackfill was not working with a wal-index
 -  ** header newer than that cached in pWal->hdr. If it were, that could
 -  ** cause a problem. The checkpointer could omit to checkpoint
 -  ** a version of page X that lies before pWal->minFrame (call that version
 -  ** A) on the basis that there is a newer version (version B) of the same
 -  ** page later in the wal file. But if version B happens to like past
 -  ** frame pWal->hdr.mxFrame - then the client would incorrectly assume
 -  ** that it can read version A from the database file. However, since
 -  ** we can guarantee that the checkpointer that set nBackfill could not
 -  ** see any pages past pWal->hdr.mxFrame, this problem does not come up.
 -  */
 -  pWal->minFrame = AtomicLoad(&pInfo->nBackfill)+1; SEH_INJECT_FAULT;
 -  walShmBarrier(pWal);
 -  if( AtomicLoad(pInfo->aReadMark+mxI)!=mxReadMark
 -   || memcmp((void *)walIndexHdr(pWal), &pWal->hdr, sizeof(WalIndexHdr))
 -  ){
 -    walUnlockShared(pWal, WAL_READ_LOCK(mxI));
 -    return WAL_RETRY;
 -  }else{
 -    assert( mxReadMark<=pWal->hdr.mxFrame );
 -    pWal->readLock = (i16)mxI;
 +      assert((rc&0xFF)!=SQLITE_BUSY||rc==SQLITE_BUSY||rc==SQLITE_BUSY_TIMEOUT);
 +      return (rc&0xFF)==SQLITE_BUSY ? WAL_RETRY : rc;
 +
 +    }
 +    /* Now that the read-lock has been obtained, check that neither the
 +    ** value in the aReadMark[] array or the contents of the wal-index
 +    ** header have changed.
 +    **
 +    ** It is necessary to check that the wal-index header did not change
 +    ** between the time it was read and when the shared-lock was obtained
 +    ** on WAL_READ_LOCK(mxI) was obtained to account for the possibility
 +    ** that the log file may have been wrapped by a writer, or that frames
 +    ** that occur later in the log than pWal->hdr.mxFrame may have been
 +    ** copied into the database by a checkpointer. If either of these things
 +    ** happened, then reading the database with the current value of
 +    ** pWal->hdr.mxFrame risks reading a corrupted snapshot. So, retry
 +    ** instead.
 +    **
 +    ** Before checking that the live wal-index header has not changed
 +    ** since it was read, set Wal.minFrame to the first frame in the wal
 +    ** file that has not yet been checkpointed. This client will not need
 +    ** to read any frames earlier than minFrame from the wal file - they
 +    ** can be safely read directly from the database file.
 +    **
 +    ** Because a ShmBarrier() call is made between taking the copy of 
 +    ** nBackfill and checking that the wal-header in shared-memory still
 +    ** matches the one cached in pWal->hdr, it is guaranteed that the 
 +    ** checkpointer that set nBackfill was not working with a wal-index
 +    ** header newer than that cached in pWal->hdr. If it were, that could
 +    ** cause a problem. The checkpointer could omit to checkpoint
 +    ** a version of page X that lies before pWal->minFrame (call that version
 +    ** A) on the basis that there is a newer version (version B) of the same
 +    ** page later in the wal file. But if version B happens to like past
 +    ** frame pWal->hdr.mxFrame - then the client would incorrectly assume
 +    ** that it can read version A from the database file. However, since
 +    ** we can guarantee that the checkpointer that set nBackfill could not
 +    ** see any pages past pWal->hdr.mxFrame, this problem does not come up.
 +    */
 +    pWal->minFrame = AtomicLoad(&pInfo->nBackfill)+1; SEH_INJECT_FAULT;
 +    walShmBarrier(pWal);
 +    if( AtomicLoad(pInfo->aReadMark+mxI)!=mxReadMark
 +     || memcmp((void *)walIndexHdr(pWal), &pWal->hdr, sizeof(WalIndexHdr))
 +    ){
 +      walUnlockShared(pWal, WAL_READ_LOCK(mxI));
 +      return WAL_RETRY;
 +    }else{
 +      assert( mxReadMark<=pWal->hdr.mxFrame );
 +      pWal->readLock = (i16)mxI;
 +    }
    }
    return rc;
  }