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Overview
Comment:Update and modernize an obsolete comment associated with VACUUM. No changes to code.
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SHA1: 94c914e3fa632f88a0d0c14537f81aa46759e2be
User & Date: drh 2013-09-30 11:01:28
Context
2013-09-30
17:37
Fix memory leaks in the amatch extension. Add a few simple test cases. check-in: 60413473 user: drh tags: trunk
11:01
Update and modernize an obsolete comment associated with VACUUM. No changes to code. check-in: 94c914e3 user: drh tags: trunk
2013-09-29
04:56
Fix typo in comment. No changes to code. check-in: 0b7bd468 user: mistachkin tags: trunk
Changes
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Changes to src/vacuum.c.

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    }
  }

  return vacuumFinalize(db, pStmt, pzErrMsg);
}

/*
** The non-standard VACUUM command is used to clean up the database,
** collapse free space, etc.  It is modelled after the VACUUM command
** in PostgreSQL.
**
** In version 1.0.x of SQLite, the VACUUM command would call
** gdbm_reorganize() on all the database tables.  But beginning
** with 2.0.0, SQLite no longer uses GDBM so this command has
** become a no-op.




















*/
void sqlite3Vacuum(Parse *pParse){
  Vdbe *v = sqlite3GetVdbe(pParse);
  if( v ){
    sqlite3VdbeAddOp2(v, OP_Vacuum, 0, 0);
    sqlite3VdbeUsesBtree(v, 0);
  }







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    }
  }

  return vacuumFinalize(db, pStmt, pzErrMsg);
}

/*
** The VACUUM command is used to clean up the database,
** collapse free space, etc.  It is modelled after the VACUUM command
** in PostgreSQL.  The VACUUM command works as follows:
**
**   (1)  Create a new transient database file
**   (2)  Copy all content from the database being vacuumed into
**        the new transient database file
**   (3)  Copy content from the transient database back into the
**        original database.
**
** The transient database requires temporary disk space approximately
** equal to the size of the original database.  The copy operation of
** step (3) requires additional temporary disk space approximately equal
** to the size of the original database for the rollback journal.
** Hence, temporary disk space that is approximately 2x the size of the
** orginal database is required.  Every page of the database is written
** approximately 3 times:  Once for step (2) and twice for step (3).
** Two writes per page are required in step (3) because the original
** database content must be written into the rollback journal prior to
** overwriting the database with the vacuumed content.
**
** Only 1x temporary space and only 1x writes would be required if
** the copy of step (3) were replace by deleting the original database
** and renaming the transient database as the original.  But that will
** not work if other processes are attached to the original database.
** And a power loss in between deleting the original and renaming the
** transient would cause the database file to appear to be deleted
** following reboot.
*/
void sqlite3Vacuum(Parse *pParse){
  Vdbe *v = sqlite3GetVdbe(pParse);
  if( v ){
    sqlite3VdbeAddOp2(v, OP_Vacuum, 0, 0);
    sqlite3VdbeUsesBtree(v, 0);
  }