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SQLite training in Houston TX on 2019-11-05 (details)
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Overview
Comment:Further performance tweaks to OP_Column.
Downloads: Tarball | ZIP archive | SQL archive
Timelines: family | ancestors | descendants | both | OP_Column-refactor
Files: files | file ages | folders
SHA1: 0e3f5df695216a27602a53eed5d25231b055adc8
User & Date: drh 2013-11-20 19:28:03
Context
2013-11-20
20:58
Improved comments on the OP_Column changes. Optimize out loading of overflow pages for content with zero length. Add test cases for the latter. check-in: 0e05679d user: drh tags: OP_Column-refactor
19:28
Further performance tweaks to OP_Column. check-in: 0e3f5df6 user: drh tags: OP_Column-refactor
17:25
Refactoring the OP_Column opcode for improved performance and maintainability. check-in: 7c914e39 user: drh tags: OP_Column-refactor
Changes
Hide Diffs Unified Diffs Ignore Whitespace Patch

Changes to src/vdbe.c.

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** If the OPFLAG_LENGTHARG and OPFLAG_TYPEOFARG bits are set on P5 when
** the result is guaranteed to only be used as the argument of a length()
** or typeof() function, respectively.  The loading of large blobs can be
** skipped for length() and all content loading can be skipped for typeof().
*/
case OP_Column: {
  i64 payloadSize64; /* Number of bytes in the record */
  int p1;            /* P1 value of the opcode */
  int p2;            /* column number to retrieve */
  VdbeCursor *pC;    /* The VDBE cursor */
  BtCursor *pCrsr;   /* The BTree cursor */
  u32 *aType;        /* aType[i] holds the numeric type of the i-th column */
  u32 *aOffset;      /* aOffset[i] is offset to start of data for i-th column */
  int nField;        /* number of fields in the record */
  int len;           /* The length of the serialized data for the column */
  int i;             /* Loop counter */
  Mem *pDest;        /* Where to write the extracted value */
  Mem sMem;          /* For storing the record being decoded */
  const u8 *zData;   /* Part of the record being decoded */
  const u8 *zHdr;    /* Next unparsed byte of the header */
  const u8 *zEndHdr; /* Pointer to first byte after the header */
  u32 offset;        /* Offset into the data */
  u32 szField;       /* Number of bytes in the content of a field */
  int avail;         /* Number of bytes of available data */
  u32 t;             /* A type code from the record header */
  Mem *pReg;         /* PseudoTable input register */

  p1 = pOp->p1;
  assert( p1<p->nCursor );
  p2 = pOp->p2;
  sMem.zMalloc = 0;
  assert( pOp->p3>0 && pOp->p3<=(p->nMem-p->nCursor) );
  pDest = &aMem[pOp->p3];
  memAboutToChange(p, pDest);

  pC = p->apCsr[p1];
  assert( pC!=0 );
  nField = pC->nField;
  assert( p2<nField );
  aType = pC->aType;
  aOffset = pC->aOffset;
#ifndef SQLITE_OMIT_VIRTUALTABLE
  assert( pC->pVtabCursor==0 );
#endif
  pCrsr = pC->pCursor;
  assert( pCrsr!=0 || pC->pseudoTableReg>0 );


  /* If the cursor cache is stale, bring it up-to-date */
  rc = sqlite3VdbeCursorMoveto(pC);
  if( rc ) goto abort_due_to_error;
  if( pC->cacheStatus!=p->cacheCtr || (pOp->p5&OPFLAG_CLEARCACHE)!=0 ){

    if( pCrsr==0 ){
      assert( pC->pseudoTableReg>0 );
      pReg = &aMem[pC->pseudoTableReg];
      if( pC->multiPseudo ){
        sqlite3VdbeMemShallowCopy(pDest, pReg+p2, MEM_Ephem);
        Deephemeralize(pDest);
        goto op_column_out;
      }
      assert( pReg->flags & MEM_Blob );
      assert( memIsValid(pReg) );
      pC->payloadSize = pC->szRow = avail = pReg->n;
      pC->aRow = (u8*)pReg->z;
    }else if( pC->nullRow ){

      MemSetTypeFlag(pDest, MEM_Null);
      goto op_column_out;

    }else{

      if( pC->isIndex ){
        assert( sqlite3BtreeCursorIsValid(pCrsr) );
        VVA_ONLY(rc =) sqlite3BtreeKeySize(pCrsr, &payloadSize64);
        assert( rc==SQLITE_OK ); /* True because of CursorMoveto() call above */
        /* sqlite3BtreeParseCellPtr() uses getVarint32() to extract the
        ** payload size, so it is impossible for payloadSize64 to be
        ** larger than 32 bits. */
................................................................................
    ** types use so much data space that there can only be 4096 and 32 of
    ** them, respectively.  So the maximum header length results from a
    ** 3-byte type for each of the maximum of 32768 columns plus three
    ** extra bytes for the header length itself.  32768*3 + 3 = 98307.
    */
    if( offset > 98307 || offset > pC->payloadSize ){
      rc = SQLITE_CORRUPT_BKPT;
      goto op_column_out;
    }
  }

  /* Make sure at least the first p2+1 entries of the header have been
  ** parsed and valid information is in aOffset[] and aType[].
  */




  if( pC->nHdrParsed<=p2 && pC->iHdrOffset<aOffset[0] ){
    /* Make sure zData points to enough of the record to cover the header. */
    if( pC->aRow==0 ){
      memset(&sMem, 0, sizeof(sMem));
      rc = sqlite3VdbeMemFromBtree(pCrsr, 0, pC->aOffset[0], pC->isIndex,&sMem);

      if( rc!=SQLITE_OK ){
        goto op_column_out;
      }
      zData = (u8*)sMem.z;
    }else{
      zData = pC->aRow;
    }

    /* Fill in aType[i] and aOffset[i] values through the p2-th field. */
    i = pC->nHdrParsed;
    offset = aOffset[i];
    zHdr = zData + pC->iHdrOffset;
    zEndHdr = zData + pC->aOffset[0];
    for(; i<=p2 && zHdr<zEndHdr; i++){

      if( zHdr[0]<0x80 ){
        t = zHdr[0];
        zHdr++;
      }else{
        zHdr += sqlite3GetVarint32(zHdr, &t);
      }
      aType[i] = t;
      szField = sqlite3VdbeSerialTypeLen(t);
      offset += szField;
      if( offset<szField ){  /* True if offset overflows */
        zHdr = &zEndHdr[1];  /* Forces SQLITE_CORRUPT return below */
        break;
      }

      aOffset[i+1] = offset;
    }

    pC->nHdrParsed = i;
    pC->iHdrOffset = (u32)(zHdr - zData);
    if( pC->aRow==0 ){
      sqlite3VdbeMemRelease(&sMem);
      sMem.flags = MEM_Null;
    }

    /* If we have read more header data than was contained in the header,
    ** or if the end of the last field appears to be past the end of the
    ** record, or if the end of the last field appears to be before the end
    ** of the record (when all fields present), then we must be dealing 
    ** with a corrupt database.
    */
    if( (zHdr > zEndHdr)
     || (offset > pC->payloadSize)
     || (zHdr==zEndHdr && offset!=pC->payloadSize)
    ){
      rc = SQLITE_CORRUPT_BKPT;













      goto op_column_out;
    }
  }

  /* Get the column information. If aOffset[p2] is non-zero, then 
  ** deserialize the value from the record. If aOffset[p2] is zero,
  ** then there are not enough fields in the record to satisfy the
  ** request.  In this case, set the value NULL or to P4 if P4 is
  ** a pointer to a Mem object.
  */
  if( p2<pC->nHdrParsed ){
    assert( rc==SQLITE_OK );
    if( pC->szRow>=aOffset[p2+1] ){
      /* This is the common case where the whole row fits on a single page */
      VdbeMemRelease(pDest);
      sqlite3VdbeSerialGet(pC->aRow+aOffset[p2], aType[p2], pDest);
    }else{
      /* This branch happens only when the row overflows onto multiple pages */
      t = aType[p2];
      if( (pOp->p5 & (OPFLAG_LENGTHARG|OPFLAG_TYPEOFARG))!=0
       && ((t>=12 && (t&1)==0) || (pOp->p5 & OPFLAG_TYPEOFARG)!=0)
      ){
        /* Content is irrelevant for the typeof() function and for
        ** the length(X) function if X is a blob.  So we might as well use
        ** bogus content rather than reading content from disk.  NULL works
        ** for text and blob and whatever is in the payloadSize64 variable
        ** will work for everything else. */
        zData = t<12 ? (u8*)&payloadSize64 : 0;

      }else{
        len = sqlite3VdbeSerialTypeLen(t);
        memset(&sMem, 0, sizeof(sMem));
        sqlite3VdbeMemMove(&sMem, pDest);
        rc = sqlite3VdbeMemFromBtree(pCrsr, aOffset[p2], len,  pC->isIndex,
                                     &sMem);
        if( rc!=SQLITE_OK ){
          goto op_column_out;
        }
        zData = (u8*)sMem.z;
      }
      sqlite3VdbeSerialGet(zData, t, pDest);
    }
    pDest->enc = encoding;
  }else{
    if( pOp->p4type==P4_MEM ){
      sqlite3VdbeMemShallowCopy(pDest, pOp->p4.pMem, MEM_Static);
    }else{
      MemSetTypeFlag(pDest, MEM_Null);
    }
  }

  /* If we dynamically allocated space to hold the data (in the
  ** sqlite3VdbeMemFromBtree() call above) then transfer control of that
  ** dynamically allocated space over to the pDest structure.
  ** This prevents a memory copy.
  */
  if( sMem.zMalloc ){
    assert( sMem.z==sMem.zMalloc );
    assert( !(pDest->flags & MEM_Dyn) );
    assert( !(pDest->flags & (MEM_Blob|MEM_Str)) || pDest->z==sMem.z );
    pDest->flags &= ~(MEM_Ephem|MEM_Static);
    pDest->flags |= MEM_Term;
    pDest->z = sMem.z;
    pDest->zMalloc = sMem.zMalloc;
  }

  rc = sqlite3VdbeMemMakeWriteable(pDest);


op_column_out:


  UPDATE_MAX_BLOBSIZE(pDest);
  REGISTER_TRACE(pOp->p3, pDest);
  break;
}

/* Opcode: Affinity P1 P2 * P4 *
** Synopsis: affinity(r[P1@P2])







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** If the OPFLAG_LENGTHARG and OPFLAG_TYPEOFARG bits are set on P5 when
** the result is guaranteed to only be used as the argument of a length()
** or typeof() function, respectively.  The loading of large blobs can be
** skipped for length() and all content loading can be skipped for typeof().
*/
case OP_Column: {
  i64 payloadSize64; /* Number of bytes in the record */

  int p2;            /* column number to retrieve */
  VdbeCursor *pC;    /* The VDBE cursor */
  BtCursor *pCrsr;   /* The BTree cursor */
  u32 *aType;        /* aType[i] holds the numeric type of the i-th column */
  u32 *aOffset;      /* aOffset[i] is offset to start of data for i-th column */

  int len;           /* The length of the serialized data for the column */
  int i;             /* Loop counter */
  Mem *pDest;        /* Where to write the extracted value */
  Mem sMem;          /* For storing the record being decoded */
  const u8 *zData;   /* Part of the record being decoded */
  const u8 *zHdr;    /* Next unparsed byte of the header */
  const u8 *zEndHdr; /* Pointer to first byte after the header */
  u32 offset;        /* Offset into the data */
  u32 szField;       /* Number of bytes in the content of a field */
  int avail;         /* Number of bytes of available data */
  u32 t;             /* A type code from the record header */
  Mem *pReg;         /* PseudoTable input register */



  p2 = pOp->p2;

  assert( pOp->p3>0 && pOp->p3<=(p->nMem-p->nCursor) );
  pDest = &aMem[pOp->p3];
  memAboutToChange(p, pDest);
  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
  pC = p->apCsr[pOp->p1];
  assert( pC!=0 );

  assert( p2<pC->nField );
  aType = pC->aType;
  aOffset = pC->aOffset;
#ifndef SQLITE_OMIT_VIRTUALTABLE
  assert( pC->pVtabCursor==0 );
#endif
  pCrsr = pC->pCursor;
  assert( pCrsr!=0 || pC->pseudoTableReg>0 );
  assert( pC->pseudoTableReg==0 || pC->nullRow );

  /* If the cursor cache is stale, bring it up-to-date */
  rc = sqlite3VdbeCursorMoveto(pC);
  if( rc ) goto abort_due_to_error;
  if( pC->cacheStatus!=p->cacheCtr || (pOp->p5&OPFLAG_CLEARCACHE)!=0 ){
    if( pC->nullRow ){
      if( pCrsr==0 ){
        assert( pC->pseudoTableReg>0 );
        pReg = &aMem[pC->pseudoTableReg];
        if( pC->multiPseudo ){
          sqlite3VdbeMemShallowCopy(pDest, pReg+p2, MEM_Ephem);
          Deephemeralize(pDest);
          goto op_column_out;
        }
        assert( pReg->flags & MEM_Blob );
        assert( memIsValid(pReg) );
        pC->payloadSize = pC->szRow = avail = pReg->n;
        pC->aRow = (u8*)pReg->z;

      }else{
        MemSetTypeFlag(pDest, MEM_Null);
        goto op_column_out;
      }
    }else{
      assert( pCrsr );
      if( pC->isIndex ){
        assert( sqlite3BtreeCursorIsValid(pCrsr) );
        VVA_ONLY(rc =) sqlite3BtreeKeySize(pCrsr, &payloadSize64);
        assert( rc==SQLITE_OK ); /* True because of CursorMoveto() call above */
        /* sqlite3BtreeParseCellPtr() uses getVarint32() to extract the
        ** payload size, so it is impossible for payloadSize64 to be
        ** larger than 32 bits. */
................................................................................
    ** types use so much data space that there can only be 4096 and 32 of
    ** them, respectively.  So the maximum header length results from a
    ** 3-byte type for each of the maximum of 32768 columns plus three
    ** extra bytes for the header length itself.  32768*3 + 3 = 98307.
    */
    if( offset > 98307 || offset > pC->payloadSize ){
      rc = SQLITE_CORRUPT_BKPT;
      goto op_column_error;
    }
  }

  /* Make sure at least the first p2+1 entries of the header have been
  ** parsed and valid information is in aOffset[] and aType[].
  */
  if( pC->nHdrParsed<=p2 ){
    /* If there is more header available for parsing, try to extract 
    ** additional fields up through the p2-th field 
    */
    if( pC->iHdrOffset<aOffset[0] ){
      /* Make sure zData points to enough of the record to cover the header. */
      if( pC->aRow==0 ){
        memset(&sMem, 0, sizeof(sMem));
        rc = sqlite3VdbeMemFromBtree(pCrsr, 0, pC->aOffset[0], pC->isIndex,
                                     &sMem);
        if( rc!=SQLITE_OK ){
          goto op_column_error;
        }
        zData = (u8*)sMem.z;
      }else{
        zData = pC->aRow;
      }
  
      /* Fill in aType[i] and aOffset[i] values through the p2-th field. */
      i = pC->nHdrParsed;
      offset = aOffset[i];
      zHdr = zData + pC->iHdrOffset;
      zEndHdr = zData + aOffset[0];
      assert( i<=p2 && zHdr<zEndHdr );
      do{
        if( zHdr[0]<0x80 ){
          t = zHdr[0];
          zHdr++;
        }else{
          zHdr += sqlite3GetVarint32(zHdr, &t);
        }
        aType[i] = t;
        szField = sqlite3VdbeSerialTypeLen(t);
        offset += szField;
        if( offset<szField ){  /* True if offset overflows */
          zHdr = &zEndHdr[1];  /* Forces SQLITE_CORRUPT return below */
          break;
        }
        i++;
        aOffset[i] = offset;

      }while( i<=p2 && zHdr<zEndHdr );
      pC->nHdrParsed = i;
      pC->iHdrOffset = (u32)(zHdr - zData);
      if( pC->aRow==0 ){
        sqlite3VdbeMemRelease(&sMem);
        sMem.flags = MEM_Null;
      }
  
      /* If we have read more header data than was contained in the header,
      ** or if the end of the last field appears to be past the end of the
      ** record, or if the end of the last field appears to be before the end
      ** of the record (when all fields present), then we must be dealing 
      ** with a corrupt database.
      */
      if( (zHdr > zEndHdr)
       || (offset > pC->payloadSize)
       || (zHdr==zEndHdr && offset!=pC->payloadSize)
      ){
        rc = SQLITE_CORRUPT_BKPT;
        goto op_column_error;
      }
    }

    /* If after nHdrParsed is still not up to p2, that means that the record
    ** has fewer than p2 columns.  So the result will be either the default
    ** value or a NULL. */
    if( pC->nHdrParsed<=p2 ){
      if( pOp->p4type==P4_MEM ){
        sqlite3VdbeMemShallowCopy(pDest, pOp->p4.pMem, MEM_Static);
      }else{
        MemSetTypeFlag(pDest, MEM_Null);
      }
      goto op_column_out;
    }
  }

  /* Get the column information. If aOffset[p2] is non-zero, then 
  ** deserialize the value from the record. If aOffset[p2] is zero,
  ** then there are not enough fields in the record to satisfy the
  ** request.  In this case, set the value NULL or to P4 if P4 is
  ** a pointer to a Mem object.
  */
  assert( p2<pC->nHdrParsed );
  assert( rc==SQLITE_OK );
  if( pC->szRow>=aOffset[p2+1] ){
    /* This is the common case where the whole row fits on a single page */
    VdbeMemRelease(pDest);
    sqlite3VdbeSerialGet(pC->aRow+aOffset[p2], aType[p2], pDest);
  }else{
    /* This branch happens only when the row overflows onto multiple pages */
    t = aType[p2];
    if( (pOp->p5 & (OPFLAG_LENGTHARG|OPFLAG_TYPEOFARG))!=0
     && ((t>=12 && (t&1)==0) || (pOp->p5 & OPFLAG_TYPEOFARG)!=0)
    ){
      /* Content is irrelevant for the typeof() function and for
      ** the length(X) function if X is a blob.  So we might as well use
      ** bogus content rather than reading content from disk.  NULL works
      ** for text and blob and whatever is in the payloadSize64 variable
      ** will work for everything else. */
      zData = t<12 ? (u8*)&payloadSize64 : 0;
      sMem.zMalloc = 0;
    }else{
      len = sqlite3VdbeSerialTypeLen(t);
      memset(&sMem, 0, sizeof(sMem));
      sqlite3VdbeMemMove(&sMem, pDest);
      rc = sqlite3VdbeMemFromBtree(pCrsr, aOffset[p2], len,  pC->isIndex,
                                   &sMem);
      if( rc!=SQLITE_OK ){
        goto op_column_error;
      }
      zData = (u8*)sMem.z;
    }
    sqlite3VdbeSerialGet(zData, t, pDest);










    /* If we dynamically allocated space to hold the data (in the
    ** sqlite3VdbeMemFromBtree() call above) then transfer control of that
    ** dynamically allocated space over to the pDest structure.
    ** This prevents a memory copy. */

    if( sMem.zMalloc ){
      assert( sMem.z==sMem.zMalloc );
      assert( !(pDest->flags & MEM_Dyn) );
      assert( !(pDest->flags & (MEM_Blob|MEM_Str)) || pDest->z==sMem.z );
      pDest->flags &= ~(MEM_Ephem|MEM_Static);
      pDest->flags |= MEM_Term;
      pDest->z = sMem.z;
      pDest->zMalloc = sMem.zMalloc;
    }
  }

  pDest->enc = encoding;

op_column_out:
  rc = sqlite3VdbeMemMakeWriteable(pDest);
op_column_error:
  UPDATE_MAX_BLOBSIZE(pDest);
  REGISTER_TRACE(pOp->p3, pDest);
  break;
}

/* Opcode: Affinity P1 P2 * P4 *
** Synopsis: affinity(r[P1@P2])

Changes to test/analyze9.test.

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  reset_db
  execsql {
    CREATE TABLE t1(a, UNIQUE(a));
    INSERT INTO t1 VALUES($two);
    ANALYZE;
  }
  set nByte2 [lindex [sqlite3_db_status db SCHEMA_USED 0] 1]


  expr {$nByte2 > $nByte+900 && $nByte2 < $nByte+1050}
} {1}

#-------------------------------------------------------------------------
# Test that stat4 data may be used with partial indexes.
#
do_test 17.1 {
  reset_db







>

|







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  reset_db
  execsql {
    CREATE TABLE t1(a, UNIQUE(a));
    INSERT INTO t1 VALUES($two);
    ANALYZE;
  }
  set nByte2 [lindex [sqlite3_db_status db SCHEMA_USED 0] 1]
  puts -nonewline " (nByte=$nByte nByte2=$nByte2)"

  expr {$nByte2 > $nByte+900 && $nByte2 < $nByte+1100}
} {1}

#-------------------------------------------------------------------------
# Test that stat4 data may be used with partial indexes.
#
do_test 17.1 {
  reset_db