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Overview
Comment:Enhance the sqlite3_analyzer.exe utility so that it computes and shows the number of bytes of metadata on btree pages and per table and index entry.
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SHA3-256:43ad41efa9e1fdd79a9804197a227491236495f14ed56c656224d6ce181703c1
User & Date: drh 2017-06-15 00:52:03
Context
2017-06-15
12:21
In the command-line shell, enhance the ".schema" command show that it shows the schema for ATTACH-ed databases in addition to "main". check-in: 48e08628 user: drh tags: trunk
00:52
Enhance the sqlite3_analyzer.exe utility so that it computes and shows the number of bytes of metadata on btree pages and per table and index entry. check-in: 43ad41ef user: drh tags: trunk
2017-06-13
16:52
Fix sqlite3rbu_close() so that the pzErrmsg parameter may be passed NULL. check-in: c433672d user: dan tags: trunk
Changes
Hide Diffs Unified Diffs Ignore Whitespace Patch

Changes to tool/spaceanal.tcl.

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  # total_pages_percent: Pages consumed as a percentage of the file.
  # storage: Bytes consumed.
  # payload_percent: Payload bytes used as a percentage of $storage.
  # total_unused: Unused bytes on pages.
  # avg_payload: Average payload per btree entry.
  # avg_fanout: Average fanout for internal pages.
  # avg_unused: Average unused bytes per btree entry.

  # ovfl_cnt_percent: Percentage of btree entries that use overflow pages.
  #
  set total_pages [expr {$leaf_pages+$int_pages+$ovfl_pages}]
  set total_pages_percent [percent $total_pages $file_pgcnt]
  set storage [expr {$total_pages*$pageSize}]
  set payload_percent [percent $payload $storage {of storage consumed}]
  set total_unused [expr {$ovfl_unused+$int_unused+$leaf_unused}]
  set avg_payload [divide $payload $nentry]
  set avg_unused [divide $total_unused $nentry]




  if {$int_pages>0} {
    # TODO: Is this formula correct?
    set nTab [mem eval "
      SELECT count(*) FROM (
          SELECT DISTINCT tblname FROM space_used WHERE $where AND is_index=0
      )
    "]
................................................................................
  if {$compressed_size!=$storage} {
    set compressed_size [expr {$compressed_size+$compressOverhead*$total_pages}]
    set pct [expr {$compressed_size*100.0/$storage}]
    set pct [format {%5.1f%%} $pct]
    statline {Bytes used after compression} $compressed_size $pct
  }
  statline {Bytes of payload} $payload $payload_percent

  if {$cnt==1} {statline {B-tree depth} $depth}
  statline {Average payload per entry} $avg_payload
  statline {Average unused bytes per entry} $avg_unused

  if {[info exists avg_fanout]} {
    statline {Average fanout} $avg_fanout
  }
  if {$showFrag && $total_pages>1} {
    set fragmentation [percent $gap_cnt [expr {$total_pages-1}]]
    statline {Non-sequential pages} $gap_cnt $fragmentation
  }
................................................................................
Bytes of payload

    The amount of payload stored under this category.  Payload is the data
    part of table entries and the key part of index entries.  The percentage
    at the right is the bytes of payload divided by the bytes of storage 
    consumed.










Average payload per entry

    The average amount of payload on each entry.  This is just the bytes of
    payload divided by the number of entries.

Average unused bytes per entry








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  # total_pages_percent: Pages consumed as a percentage of the file.
  # storage: Bytes consumed.
  # payload_percent: Payload bytes used as a percentage of $storage.
  # total_unused: Unused bytes on pages.
  # avg_payload: Average payload per btree entry.
  # avg_fanout: Average fanout for internal pages.
  # avg_unused: Average unused bytes per btree entry.
  # avg_meta: Average metadata overhead per entry.
  # ovfl_cnt_percent: Percentage of btree entries that use overflow pages.
  #
  set total_pages [expr {$leaf_pages+$int_pages+$ovfl_pages}]
  set total_pages_percent [percent $total_pages $file_pgcnt]
  set storage [expr {$total_pages*$pageSize}]
  set payload_percent [percent $payload $storage {of storage consumed}]
  set total_unused [expr {$ovfl_unused+$int_unused+$leaf_unused}]
  set avg_payload [divide $payload $nentry]
  set avg_unused [divide $total_unused $nentry]
  set total_meta [expr {$storage - $payload - $total_unused}]
  set total_meta [expr {$total_meta + 4*($ovfl_pages - $ovfl_cnt)}]
  set meta_percent [percent $total_meta $storage {of metadata}]
  set avg_meta [divide $total_meta $nentry]
  if {$int_pages>0} {
    # TODO: Is this formula correct?
    set nTab [mem eval "
      SELECT count(*) FROM (
          SELECT DISTINCT tblname FROM space_used WHERE $where AND is_index=0
      )
    "]
................................................................................
  if {$compressed_size!=$storage} {
    set compressed_size [expr {$compressed_size+$compressOverhead*$total_pages}]
    set pct [expr {$compressed_size*100.0/$storage}]
    set pct [format {%5.1f%%} $pct]
    statline {Bytes used after compression} $compressed_size $pct
  }
  statline {Bytes of payload} $payload $payload_percent
  statline {Bytes of metadata} $total_meta $meta_percent
  if {$cnt==1} {statline {B-tree depth} $depth}
  statline {Average payload per entry} $avg_payload
  statline {Average unused bytes per entry} $avg_unused
  statline {Average metadata per entry} $avg_meta
  if {[info exists avg_fanout]} {
    statline {Average fanout} $avg_fanout
  }
  if {$showFrag && $total_pages>1} {
    set fragmentation [percent $gap_cnt [expr {$total_pages-1}]]
    statline {Non-sequential pages} $gap_cnt $fragmentation
  }
................................................................................
Bytes of payload

    The amount of payload stored under this category.  Payload is the data
    part of table entries and the key part of index entries.  The percentage
    at the right is the bytes of payload divided by the bytes of storage 
    consumed.

Bytes of metadata

    The amount of formatting and structural information stored on for the
    table or index.  Metadata includes the btree page header, the cell pointer
    array, the size field for each cell, the left child pointer or non-leaf
    cells, the overflow pointers for overflow cells, and the rowid value for
    rowid table cells.  In other words, metadata is everything that is not
    unused space and that is not content.

Average payload per entry

    The average amount of payload on each entry.  This is just the bytes of
    payload divided by the number of entries.

Average unused bytes per entry