polardbxengine/storage/innobase/include/page0zip.ic

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/** @file include/page0zip.ic
 Compressed page interface

 Created June 2005 by Marko Makela
 *******************************************************/

#ifdef UNIV_MATERIALIZE
#undef UNIV_INLINE
#define UNIV_INLINE
#endif

#include "mtr0log.h"
#include "page0page.h"
#include "page0zip.h"
#include "srv0srv.h"

/* The format of compressed pages is as follows.

The header and trailer of the uncompressed pages, excluding the page
directory in the trailer, are copied as is to the header and trailer
of the compressed page.

At the end of the compressed page, there is a dense page directory
pointing to every user record contained on the page, including deleted
records on the free list.  The dense directory is indexed in the
collation order, i.e., in the order in which the record list is
linked on the uncompressed page.  The infimum and supremum records are
excluded.  The two most significant bits of the entries are allocated
for the delete-mark and an n_owned flag indicating the last record in
a chain of records pointed to from the sparse page directory on the
uncompressed page.

The data between PAGE_ZIP_START and the last page directory entry will
be written in compressed format, starting at offset PAGE_DATA.
Infimum and supremum records are not stored.  We exclude the
REC_N_NEW_EXTRA_BYTES in every record header.  These can be recovered
from the dense page directory stored at the end of the compressed
page.

The fields node_ptr (in non-leaf B-tree nodes; level>0), trx_id and
roll_ptr (in leaf B-tree nodes; level=0), and BLOB pointers of
externally stored columns are stored separately, in ascending order of
heap_no and column index, starting backwards from the dense page
directory.

The compressed data stream may be followed by a modification log
covering the compressed portion of the page, as follows.

MODIFICATION LOG ENTRY FORMAT
- write record:
  - (heap_no - 1) << 1 (1..2 bytes)
  - extra bytes backwards
  - data bytes
- clear record:
  - (heap_no - 1) << 1 | 1 (1..2 bytes)

The integer values are stored in a variable-length format:
- 0xxxxxxx: 0..127
- 1xxxxxxx xxxxxxxx: 0..32767

The end of the modification log is marked by a 0 byte.

In summary, the compressed page looks like this:

(1) Uncompressed page header (PAGE_DATA bytes)
(2) Compressed index information
(3) Compressed page data
(4) Page modification log (page_zip->m_start..page_zip->m_end)
(5) Empty zero-filled space
(6) BLOB pointers (on leaf pages)
  - BTR_EXTERN_FIELD_REF_SIZE for each externally stored column
  - in descending collation order
(7) Uncompressed columns of user records, n_dense * uncompressed_size bytes,
  - indexed by heap_no
  - DATA_TRX_ID_LEN + DATA_ROLL_PTR_LEN + DATA_SCN_ID_LEN + DATA_UNDO_PTR_LEN
    for leaf pages of clustered indexes
  - REC_NODE_PTR_SIZE for non-leaf pages
  - 0 otherwise
(8) dense page directory, stored backwards
  - n_dense = n_heap - 2
  - existing records in ascending collation order
  - deleted records (free list) in link order
*/

/** Set the size of a compressed page in bytes. */
UNIV_INLINE
void page_zip_set_size(page_zip_des_t *page_zip, /*!< in/out: compressed page */
                       ulint size)               /*!< in: size in bytes */
{
  if (size) {
    int ssize;

    ut_ad(ut_is_2pow(size));

    for (ssize = 1; size > (ulint)(512 << ssize); ssize++) {
    }

    page_zip->ssize = ssize;
  } else {
    page_zip->ssize = 0;
  }

  ut_ad(page_zip_get_size(page_zip) == size);
}

#ifndef UNIV_HOTBACKUP
/** Determine if a record is so big that it needs to be stored externally.
@param[in]	rec_size	length of the record in bytes
@param[in]	comp		nonzero=compact format
@param[in]	n_fields	number of fields in the record; ignored if
tablespace is not compressed
@param[in]	page_size	page size
@return false if the entire record can be stored locally on the page */
UNIV_INLINE
ibool page_zip_rec_needs_ext(ulint rec_size, ulint comp, ulint n_fields,
                             const page_size_t &page_size) {
  ut_ad(rec_size > (comp ? REC_N_NEW_EXTRA_BYTES : REC_N_OLD_EXTRA_BYTES));
  ut_ad(comp || !page_size.is_compressed());

  if (UNIV_PAGE_SIZE_MAX > REC_MAX_DATA_SIZE && rec_size >= REC_MAX_DATA_SIZE) {
    return (TRUE);
  }

  if (page_size.is_compressed()) {
    ut_ad(comp);
    /* On a compressed page, there is a two-byte entry in
    the dense page directory for every record.  But there
    is no record header.  There should be enough room for
    one record on an empty leaf page.  Subtract 1 byte for
    the encoded heap number.  Check also the available space
    on the uncompressed page. */
    return (rec_size - (REC_N_NEW_EXTRA_BYTES - 2 - 1) >=
                page_zip_empty_size(n_fields, page_size.physical()) ||
            rec_size >= page_get_free_space_of_empty(TRUE) / 2);
  }

  return (rec_size >= page_get_free_space_of_empty(comp) / 2);
}
#endif /* !UNIV_HOTBACKUP */

/** Determine if the length of the page trailer.
 @return length of the page trailer, in bytes, not including the
 terminating zero byte of the modification log */
UNIV_INLINE
ibool page_zip_get_trailer_len(
    const page_zip_des_t *page_zip, /*!< in: compressed page */
    bool is_clust)                  /*!< in: TRUE if clustered index */
{
  ulint uncompressed_size;

  ut_ad(page_zip_simple_validate(page_zip));
  UNIV_MEM_ASSERT_RW(page_zip->data, page_zip_get_size(page_zip));

  if (!page_is_leaf(page_zip->data)) {
    uncompressed_size = PAGE_ZIP_DIR_SLOT_SIZE + REC_NODE_PTR_SIZE;
    ut_ad(!page_zip->n_blobs);
  } else if (is_clust) {
    uncompressed_size = PAGE_ZIP_DIR_SLOT_SIZE + PAGE_ZIP_TRX_FIELDS_SIZE;
  } else {
    uncompressed_size = PAGE_ZIP_DIR_SLOT_SIZE;
    ut_ad(!page_zip->n_blobs);
  }

  return ((page_dir_get_n_heap(page_zip->data) - 2) * uncompressed_size +
          page_zip->n_blobs * BTR_EXTERN_FIELD_REF_SIZE);
}

/** Determine how big record can be inserted without recompressing the page.
 @return a positive number indicating the maximum size of a record
 whose insertion is guaranteed to succeed, or zero or negative */
UNIV_INLINE
lint page_zip_max_ins_size(
    const page_zip_des_t *page_zip, /*!< in: compressed page */
    ibool is_clust)                 /*!< in: TRUE if clustered index */
{
  ulint trailer_len;

  trailer_len = page_zip_get_trailer_len(page_zip, is_clust);

  /* When a record is created, a pointer may be added to
  the dense directory.
  Likewise, space for the columns that will not be
  compressed will be allocated from the page trailer.
  Also the BLOB pointers will be allocated from there, but
  we may as well count them in the length of the record. */

  trailer_len += PAGE_ZIP_DIR_SLOT_SIZE;

  return ((lint)page_zip_get_size(page_zip) - trailer_len - page_zip->m_end -
          (REC_N_NEW_EXTRA_BYTES - 2));
}

/** Determine if enough space is available in the modification log.
 @return true if enough space is available */
UNIV_INLINE
ibool page_zip_available(
    const page_zip_des_t *page_zip, /*!< in: compressed page */
    bool is_clust,                  /*!< in: TRUE if clustered index */
    ulint length,                   /*!< in: combined size of the record */
    ulint create)                   /*!< in: nonzero=add the record to
                                    the heap */
{
  ulint trailer_len;

  ut_ad(length > REC_N_NEW_EXTRA_BYTES);

  trailer_len = page_zip_get_trailer_len(page_zip, is_clust);

  /* Subtract the fixed extra bytes and add the maximum
  space needed for identifying the record (encoded heap_no). */
  length -= REC_N_NEW_EXTRA_BYTES - 2;

  if (create > 0) {
    /* When a record is created, a pointer may be added to
    the dense directory.
    Likewise, space for the columns that will not be
    compressed will be allocated from the page trailer.
    Also the BLOB pointers will be allocated from there, but
    we may as well count them in the length of the record. */

    trailer_len += PAGE_ZIP_DIR_SLOT_SIZE;
  }

  return (length + trailer_len + page_zip->m_end < page_zip_get_size(page_zip));
}

/** Initialize a compressed page descriptor. */
UNIV_INLINE
void page_zip_des_init(page_zip_des_t *page_zip) /*!< in/out: compressed page
                                                 descriptor */
{
  memset(page_zip, 0, sizeof *page_zip);
}

/** Write a log record of writing to the uncompressed header portion of a page.
 */
void page_zip_write_header_log(
    const byte *data, /*!< in: data on the uncompressed page */
    ulint length,     /*!< in: length of the data */
    mtr_t *mtr);      /*!< in: mini-transaction */

/** Write data to the uncompressed header portion of a page.  The data must
already have been written to the uncompressed page.
@param[in,out]	page_zip	compressed page
@param[in]	str		address on the uncompressed page
@param[in]	length		length of the data
@param[in]	mtr		mini-transaction, or NULL */
UNIV_INLINE
void page_zip_write_header(page_zip_des_t *page_zip, const byte *str,
                           ulint length, mtr_t *mtr) {
  ulint pos;

  ut_ad(page_zip_simple_validate(page_zip));
  UNIV_MEM_ASSERT_RW(page_zip->data, page_zip_get_size(page_zip));

  pos = page_offset(str);

  ut_ad(pos < PAGE_DATA);

  memcpy(page_zip->data + pos, str, length);

  /* The following would fail in page_cur_insert_rec_zip(). */
  /* ut_ad(page_zip_validate(page_zip, str - pos)); */

  if (mtr) {
#ifndef UNIV_HOTBACKUP
    page_zip_write_header_log(str, length, mtr);
#endif /* !UNIV_HOTBACKUP */
  }
}

/** Write a log record of compressing an index page without the data on the
 * page.
 */
UNIV_INLINE
void page_zip_compress_write_log_no_data(
    ulint level,         /*!< in: compression level */
    const page_t *page,  /*!< in: page that is compressed */
    dict_index_t *index, /*!< in: index */
    mtr_t *mtr)          /*!< in: mtr */
{
#ifndef UNIV_HOTBACKUP
  byte *log_ptr = mlog_open_and_write_index(mtr, page, index,
                                            MLOG_ZIP_PAGE_COMPRESS_NO_DATA, 1);

  if (log_ptr) {
    mach_write_to_1(log_ptr, level);
    mlog_close(mtr, log_ptr + 1);
  }
#endif /* !UNIV_HOTBACKUP */
}

/** Parses a log record of compressing an index page without the data.
 @return end of log record or NULL */
UNIV_INLINE
byte *page_zip_parse_compress_no_data(
    byte *ptr,                /*!< in: buffer */
    byte *end_ptr,            /*!< in: buffer end */
    page_t *page,             /*!< in: uncompressed page */
    page_zip_des_t *page_zip, /*!< out: compressed page */
    dict_index_t *index)      /*!< in: index */
{
  ulint level;
  if (end_ptr == ptr) {
    return (NULL);
  }

  level = mach_read_from_1(ptr);

  /* If page compression fails then there must be something wrong
  because a compress log record is logged only if the compression
  was successful. Crash in this case. */

  if (page && !page_zip_compress(page_zip, page, index, level, NULL)) {
    ut_error;
  }

  return (ptr + 1);
}

#ifndef UNIV_HOTBACKUP
/** Reset the counters used for filling
 INFORMATION_SCHEMA.innodb_cmp_per_index. */
UNIV_INLINE
void page_zip_reset_stat_per_index() {
  mutex_enter(&page_zip_stat_per_index_mutex);

  page_zip_stat_per_index.erase(page_zip_stat_per_index.begin(),
                                page_zip_stat_per_index.end());

  mutex_exit(&page_zip_stat_per_index_mutex);
}
#endif /* !UNIV_HOTBACKUP */

/** Find the slot of the given record in the dense page directory.
 @return dense directory slot, or NULL if record not found */
UNIV_INLINE
byte *page_zip_dir_find_low(byte *slot,   /*!< in: start of records */
                            byte *end,    /*!< in: end of records */
                            ulint offset) /*!< in: offset of user record */
{
  ut_ad(slot <= end);

  for (; slot < end; slot += PAGE_ZIP_DIR_SLOT_SIZE) {
    if ((mach_read_from_2(slot) & PAGE_ZIP_DIR_SLOT_MASK) == offset) {
      return (slot);
    }
  }

  return (NULL);
}

/** Gets the size of the compressed page trailer (the dense page directory),
 only including user records (excluding the free list).
 @return length of dense page directory comprising existing records, in bytes */
UNIV_INLINE
ulint page_zip_dir_user_size(
    const page_zip_des_t *page_zip) /*!< in: compressed page */
{
  ulint size = PAGE_ZIP_DIR_SLOT_SIZE * page_get_n_recs(page_zip->data);
  ut_ad(size <= page_zip_dir_size(page_zip));
  return (size);
}

/** Find the slot of the given free record in the dense page directory.
 @return dense directory slot, or NULL if record not found */
UNIV_INLINE
byte *page_zip_dir_find_free(
    page_zip_des_t *page_zip, /*!< in: compressed page */
    ulint offset)             /*!< in: offset of user record */
{
  byte *end = page_zip->data + page_zip_get_size(page_zip);

  ut_ad(page_zip_simple_validate(page_zip));

  return (page_zip_dir_find_low(end - page_zip_dir_size(page_zip),
                                end - page_zip_dir_user_size(page_zip),
                                offset));
}

/** Gets an offset to the compressed page trailer (the dense page directory),
 including deleted records (the free list).
 @return offset of the dense page directory */
UNIV_INLINE
ulint page_zip_dir_start_offs(
    const page_zip_des_t *page_zip, /*!< in: compressed page */
    ulint n_dense)                  /*!< in: directory size */
{
  ut_ad(n_dense * PAGE_ZIP_DIR_SLOT_SIZE < page_zip_get_size(page_zip));

  return (page_zip_get_size(page_zip) - n_dense * PAGE_ZIP_DIR_SLOT_SIZE);
}

#ifdef UNIV_MATERIALIZE
#undef UNIV_INLINE
#define UNIV_INLINE UNIV_INLINE_ORIGINAL
#endif