[sql] SQLite patch to implement "smart" auto-vacuum.

third_party/sqlite/patches/0011-Allow-auto-vacuum-to-work-with-chunks.patch

+From d62ff0d64a8738fd8bb07b82bcebd65143a17045 Mon Sep 17 00:00:00 2001
+From: Scott Hess <shess@chromium.org>
+Date: Thu, 2 Mar 2017 15:23:09 -0800
+Subject: [PATCH 11/11] Allow auto-vacuum to work with chunks.
+
+SQLITE_FCNTL_CHUNK_SIZE can advise the VFS to resize files in quantum
+amounts, to reduce fragmentation from tiny appends.  This change allows
+a new PRAGMA auto_vacuum_slack_pages to provide auto_vacuum with a hint
+to only rearrange pages when an entire quantum can be released.
+
+BUG=698010
+---
+ third_party/sqlite/src/src/btree.c    | 56 ++++++++++++++++++++++++++++++++++-
+ third_party/sqlite/src/src/btree.h    |  2 ++
+ third_party/sqlite/src/src/btreeInt.h |  1 +
+ third_party/sqlite/src/src/pragma.c   | 21 +++++++++++++
+ third_party/sqlite/src/src/pragma.h   |  8 +++++
+ 5 files changed, 87 insertions(+), 1 deletion(-)
+
+diff --git a/third_party/sqlite/src/src/btree.c b/third_party/sqlite/src/src/btree.c
+index de553423b884..3335ced417ca 100644
+--- a/third_party/sqlite/src/src/btree.c
++++ b/third_party/sqlite/src/src/btree.c
+@@ -2812,6 +2812,46 @@ int sqlite3BtreeGetAutoVacuum(Btree *p){
+ #endif
+ }
+ 
++/*
++** Change the 'auto-vacuum-slack-pages' property of the database. If auto vacuum
++** is enabled, this is the number of chunks of slack to allow before
++** automatically running an incremental vacuum.
++*/
++int sqlite3BtreeSetAutoVacuumSlackPages(Btree *p, int autoVacuumSlack){
++#ifdef SQLITE_OMIT_AUTOVACUUM
++  return SQLITE_READONLY;
++#else
++  BtShared *pBt = p->pBt;
++  int rc = SQLITE_OK;
++  u8 avs = (u8)autoVacuumSlack;
++  if( autoVacuumSlack>avs ){
++    avs = 0xFF;
++  }
++
++  sqlite3BtreeEnter(p);
++  pBt->autoVacuumSlack = avs;
++  sqlite3BtreeLeave(p);
++  return rc;
++#endif
++}
++
++/*
++** Return the value of the 'auto-vacuum-slack-pages' property.
++*/
++int sqlite3BtreeGetAutoVacuumSlackPages(Btree *p){
++#ifdef SQLITE_OMIT_AUTOVACUUM
++  return 0;
++#else
++  int rc = 0;
++  sqlite3BtreeEnter(p);
++  if( p->pBt->autoVacuum!=0 ){
++    rc = p->pBt->autoVacuumSlack;
++  }
++  sqlite3BtreeLeave(p);
++  return rc;
++#endif
++}
++
+ 
+ /*
+ ** Get a reference to pPage1 of the database file.  This will
+@@ -3653,13 +3693,27 @@ int sqlite3BtreeIncrVacuum(Btree *p){
+ */
+ static int autoVacuumCommit(BtShared *pBt){
+   int rc = SQLITE_OK;
++  int bShouldVacuum = pBt->autoVacuum && !pBt->incrVacuum;
+   Pager *pPager = pBt->pPager;
+   VVA_ONLY( int nRef = sqlite3PagerRefcount(pPager); )
+ 
+   assert( sqlite3_mutex_held(pBt->mutex) );
+   invalidateAllOverflowCache(pBt);
+   assert(pBt->autoVacuum);
+-  if( !pBt->incrVacuum ){
++  if( bShouldVacuum && pBt->autoVacuumSlack ){
++    Pgno nOrig;        /* Database size before freeing */
++    Pgno nFree;        /* Number of pages on the freelist initially */
++
++    nOrig = btreePagecount(pBt);
++    nFree = get4byte(&pBt->pPage1->aData[36]);
++    bShouldVacuum =
++        (nOrig-nFree-1)/pBt->autoVacuumSlack < (nOrig-1)/pBt->autoVacuumSlack;
++    /* TODO: When integrating this test with the following code, contrive to
++    ** trim to the integral chunk boundary, rather than trimming the entire free
++    ** list.
++    */
++  }
++  if( bShouldVacuum ){
+     Pgno nFin;         /* Number of pages in database after autovacuuming */
+     Pgno nFree;        /* Number of pages on the freelist initially */
+     Pgno iFree;        /* The next page to be freed */
+diff --git a/third_party/sqlite/src/src/btree.h b/third_party/sqlite/src/src/btree.h
+index ae57468e3fd5..e0da44957564 100644
+--- a/third_party/sqlite/src/src/btree.h
++++ b/third_party/sqlite/src/src/btree.h
+@@ -78,6 +78,8 @@ int sqlite3BtreeGetOptimalReserve(Btree*);
+ int sqlite3BtreeGetReserveNoMutex(Btree *p);
+ int sqlite3BtreeSetAutoVacuum(Btree *, int);
+ int sqlite3BtreeGetAutoVacuum(Btree *);
++int sqlite3BtreeSetAutoVacuumSlackPages(Btree *, int);
++int sqlite3BtreeGetAutoVacuumSlackPages(Btree *);
+ int sqlite3BtreeBeginTrans(Btree*,int);
+ int sqlite3BtreeCommitPhaseOne(Btree*, const char *zMaster);
+ int sqlite3BtreeCommitPhaseTwo(Btree*, int);
+diff --git a/third_party/sqlite/src/src/btreeInt.h b/third_party/sqlite/src/src/btreeInt.h
+index b01163c33f49..eb9d1b5ef58d 100644
+--- a/third_party/sqlite/src/src/btreeInt.h
++++ b/third_party/sqlite/src/src/btreeInt.h
+@@ -412,6 +412,7 @@ struct BtShared {
+   u8 openFlags;         /* Flags to sqlite3BtreeOpen() */
+ #ifndef SQLITE_OMIT_AUTOVACUUM
+   u8 autoVacuum;        /* True if auto-vacuum is enabled */
++  u8 autoVacuumSlack;   /* Optional pages of slack for auto-vacuum */
+   u8 incrVacuum;        /* True if incr-vacuum is enabled */
+   u8 bDoTruncate;       /* True to truncate db on commit */
+ #endif
+diff --git a/third_party/sqlite/src/src/pragma.c b/third_party/sqlite/src/src/pragma.c
+index b1775a4082a3..1d5ebfca098d 100644
+--- a/third_party/sqlite/src/src/pragma.c
++++ b/third_party/sqlite/src/src/pragma.c
+@@ -736,6 +736,27 @@ void sqlite3Pragma(
+   }
+ #endif
+ 
++  /*
++  **  PRAGMA [schema.]auto_vacuum_slack_pages(N)
++  **
++  ** Control chunk size of auto-vacuum.
++  */
++#ifndef SQLITE_OMIT_AUTOVACUUM
++  case PragTyp_AUTO_VACUUM_SLACK_PAGES: {
++    Btree *pBt = pDb->pBt;
++    assert( pBt!=0 );
++    if( !zRight ){
++      returnSingleInt(v, sqlite3BtreeGetAutoVacuumSlackPages(pBt));
++    }else{
++      int nPages = 8;
++      if( sqlite3GetInt32(zRight, &nPages) ){
++        sqlite3BtreeSetAutoVacuumSlackPages(pBt, nPages);
++      }
++    }
++    break;
++  }
++#endif
++
+ #ifndef SQLITE_OMIT_PAGER_PRAGMAS
+   /*
+   **  PRAGMA [schema.]cache_size
+diff --git a/third_party/sqlite/src/src/pragma.h b/third_party/sqlite/src/src/pragma.h
+index 5d8d0aa35b3f..e47f80fefac4 100644
+--- a/third_party/sqlite/src/src/pragma.h
++++ b/third_party/sqlite/src/src/pragma.h
+@@ -48,6 +48,7 @@
+ #define PragTyp_REKEY                         40
+ #define PragTyp_LOCK_STATUS                   41
+ #define PragTyp_PARSER_TRACE                  42
++#define PragTyp_AUTO_VACUUM_SLACK_PAGES       43
+ 
+ /* Property flags associated with various pragma. */
+ #define PragFlg_NeedSchema 0x01 /* Force schema load before running */
+@@ -145,6 +146,13 @@ static const PragmaName aPragmaName[] = {
+   /* ColNames:  */ 0, 0,
+   /* iArg:      */ 0 },
+ #endif
++#if !defined(SQLITE_OMIT_AUTOVACUUM)
++  { /* zName:     */ "auto_vacuum_slack_pages",
++    /* ePragTyp:  */ PragTyp_AUTO_VACUUM_SLACK_PAGES,
++    /* ePragFlg:  */ PragFlg_NeedSchema|PragFlg_Result0|PragFlg_SchemaReq|PragFlg_NoColumns1,
++    /* ColNames:  */ 0, 0,
++    /* iArg:      */ 0 },
++#endif
+ #if !defined(SQLITE_OMIT_FLAG_PRAGMAS)
+ #if !defined(SQLITE_OMIT_AUTOMATIC_INDEX)
+  {/* zName:     */ "automatic_index",
+-- 
+2.11.0
+