In wal mode, if a "BEGIN EXCLUSIVE" command (or any other command that

upgrades from no transaction directly to a write transaction) hits an
SQLITE_BUSY_SNAPSHOT error, change the error code to SQLITE_BUSY to indicate
to the caller that the condition may be transient.

FossilOrigin-Name: e6108047cb136119d8ed19af010a669ed9750b4e7f991ccabc9e3d15774eda31

diff --cc manifest
index 2357a1bfd45638db86fadd3a4c29a9f9847674f0,b888f1874b92ad4ee035f21b0fc8faa24a2afc9b..64d53e2fec5cd1a00ce1589aa49188ee414dbef9
--- 1/manifest
--- 2/manifest
+++ b/manifest
@@@ -1,5 -1,5 +1,5 @@@
- C Test\sthat\sa\srace\scondition\scan\scause\sa\s"BEGIN\sEXCLUSIVE"\sto\sreturn\nSQLITE_BUSY_SNAPSHOT\sin\swal\smode.
- D 2018-07-03T20:17:27.649
 -C Fix\sa\stypo\sinside\san\sassert()\sstatement\sintroduced\sby\sthe\sprevious\scommit.
 -D 2018-07-05T17:03:43.644
++C In\swal\smode,\sif\sa\s"BEGIN\sEXCLUSIVE"\scommand\s(or\sany\sother\scommand\sthat\nupgrades\sfrom\sno\stransaction\sdirectly\sto\sa\swrite\stransaction)\shits\san\nSQLITE_BUSY_SNAPSHOT\serror,\schange\sthe\serror\scode\sto\sSQLITE_BUSY\sto\sindicate\nto\sthe\scaller\sthat\sthe\scondition\smay\sbe\stransient.
++D 2018-07-05T17:16:55.340
  F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
  F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
  F Makefile.in 0a3a6c81e6fcb969ff9106e882f0a08547014ba463cb6beca4c4efaecc924ee6
@@@ -436,7 -436,7 +436,7 @@@ F src/auth.c a38f3c63c974787ecf75e3213f
  F src/backup.c 78d3cecfbe28230a3a9a1793e2ead609f469be43e8f486ca996006be551857ab
  F src/bitvec.c 17ea48eff8ba979f1f5b04cc484c7bb2be632f33
  F src/btmutex.c 8acc2f464ee76324bf13310df5692a262b801808984c1b79defb2503bbafadb6
- F src/btree.c bb23e5470ec0c9b9ae8e17c86cb686bc4112642d8f457bd42b3b3727d5ef78be
 -F src/btree.c 757b29862c2fa6db149cf92117a6d22591bcad4b5ff1388fd480e479852a9694
++F src/btree.c 0c27fb9b4bfd610261e2ac8956090fbf04b607b0d12bc0f1d77b6c5bf3ab3c7d
  F src/btree.h febb2e817be499570b7a2e32a9bbb4b607a9234f6b84bb9ae84916d4806e96f2
  F src/btreeInt.h 620ab4c7235f43572cf3ac2ac8723cbdf68073be4d29da24897c7b77dda5fd96
  F src/build.c 3b3bfa88800739e1f11313dcecfba5ef8e4757b6c929cdf7de9fcfc01002b81f
@@@ -1745,7 -1745,7 +1745,8 @@@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a9
  F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
  F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
  F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
- P b6563647382634588ebe5c6a3c35c65a321dc1b3732c809d48ce46759b9dd80f
- R 85d71bbec8ad4dcf2f8e9507c907b291
 -P 221ff63e7902226ebf728bb7442727420636831163708f360724506ce9487ab6
 -R 6292256afd58b3bdc21661c68c4c01f5
++P 5a12db75d1da65daa92413a6b5892309e9d9479bb3610764e1015abe5bf28dbe e3357728472d5e57db6d7eef0ce008bdee071b5b07b60e242f383440eebe85bd
++R 033b09a0f95c9e18f2482abfb8812158
++T +closed e3357728472d5e57db6d7eef0ce008bdee071b5b07b60e242f383440eebe85bd
  U dan
- Z 38cb85199c9d8fc14bf46fba2bfb3f49
 -Z 7030dc2937cfaf6aca4912e5a05c04a5
++Z e957a80e23c286301ec669959e08c13c

diff --cc manifest.uuid
index e6f611aeb3068299f474cc80de0323a8778727e4,8c9534cf91879b10790e232f4c7e756e6f15ca0c..84b34c2982c6bae603a5a96542b40c631689baa5
--- 1/manifest.uuid
--- 2/manifest.uuid
+++ b/manifest.uuid
@@@ -1,1 -1,1 +1,1 @@@
- 5a12db75d1da65daa92413a6b5892309e9d9479bb3610764e1015abe5bf28dbe
 -e3357728472d5e57db6d7eef0ce008bdee071b5b07b60e242f383440eebe85bd
++e6108047cb136119d8ed19af010a669ed9750b4e7f991ccabc9e3d15774eda31

diff --cc src/btree.c
index d2c580d11d470a70099765bc9a17eaadc578f312,27e20e8ace7f5d7f6ddf09b1ae008f66b68f45a6..20cc3eb106af95a394d58d59a482570ef076367c
--- 1/src/btree.c
--- 2/src/btree.c
+++ b/src/btree.c
@@@ -3375,6 -3375,6 +3375,11 @@@ int sqlite3BtreeBeginTrans(Btree *p, in
          rc = sqlite3PagerBegin(pBt->pPager,wrflag>1,sqlite3TempInMemory(p->db));
          if( rc==SQLITE_OK ){
            rc = newDatabase(pBt);
++        }else if( rc==SQLITE_BUSY_SNAPSHOT && pBt->inTransaction==TRANS_NONE ){
++          /* if there was no transaction opened when this function was
++          ** called and SQLITE_BUSY_SNAPSHOT is returned, change the error
++          ** code to SQLITE_BUSY. */
++          rc = SQLITE_BUSY;
          }
        }
      }
@@@ -3424,9 -3424,17 +3429,8 @@@
          }
        }
      }
 -  }else if( rc==SQLITE_BUSY_SNAPSHOT && pBt->inTransaction==TRANS_NONE ){
 -    /* Even if there was no transaction opened when this function was
 -    ** called, a race condition may cause an SQLITE_BUSY_SNAPSHOT error
 -    ** in wal mode (since the code above opens a read-transaction and then
 -    ** upgrades it to a write-transaction - it does not take the write lock
 -    ** atomically). In this case change the error code to SQLITE_BUSY.  */
 -    assert( wrflag );
 -    rc = SQLITE_BUSY;
    }
  
--
  trans_begun:
    if( rc==SQLITE_OK ){
      if( pSchemaVersion ){