Home • Explore • Blog • CI
☰



postgresql
85th chunk of `doc/src/sgml/monitoring.sgml`
193df17e2b25e40ae0cc81b909bc2d3b8f3e7ca21a129b200000000100000fa2
    arg2, arg3, and arg4 contain the tablespace, database, and relation OIDs
      identifying the relation.
      arg5 is the ID of the backend which created the temporary relation for a
      local buffer, or <symbol>INVALID_PROC_NUMBER</symbol> (-1) for a shared buffer.
      arg6 is the number of bytes actually read, while arg7 is the number
      requested (if these are different it indicates a short read).</entry>
    </row>
    <row>
     <entry><literal>smgr-md-write-start</literal></entry>
     <entry><literal>(ForkNumber, BlockNumber, Oid, Oid, Oid, int)</literal></entry>
     <entry>Probe that fires when beginning to write a block to a relation.
      arg0 and arg1 contain the fork and block numbers of the page.
      arg2, arg3, and arg4 contain the tablespace, database, and relation OIDs
      identifying the relation.
      arg5 is the ID of the backend which created the temporary relation for a
      local buffer, or <symbol>INVALID_PROC_NUMBER</symbol> (-1) for a shared buffer.</entry>
    </row>
    <row>
     <entry><literal>smgr-md-write-done</literal></entry>
     <entry><literal>(ForkNumber, BlockNumber, Oid, Oid, Oid, int, int, int)</literal></entry>
     <entry>Probe that fires when a block write is complete.
      arg0 and arg1 contain the fork and block numbers of the page.
      arg2, arg3, and arg4 contain the tablespace, database, and relation OIDs
      identifying the relation.
      arg5 is the ID of the backend which created the temporary relation for a
      local buffer, or <symbol>INVALID_PROC_NUMBER</symbol> (-1) for a shared buffer.
      arg6 is the number of bytes actually written, while arg7 is the number
      requested (if these are different it indicates a short write).</entry>
    </row>
    <row>
     <entry><literal>sort-start</literal></entry>
     <entry><literal>(int, bool, int, int, bool, int)</literal></entry>
     <entry>Probe that fires when a sort operation is started.
      arg0 indicates heap, index or datum sort.
      arg1 is true for unique-value enforcement.
      arg2 is the number of key columns.
      arg3 is the number of kilobytes of work memory allowed.
      arg4 is true if random access to the sort result is required.
      arg5 indicates serial when <literal>0</literal>, parallel worker when
      <literal>1</literal>, or parallel leader when <literal>2</literal>.</entry>
    </row>
    <row>
     <entry><literal>sort-done</literal></entry>
     <entry><literal>(bool, long)</literal></entry>
     <entry>Probe that fires when a sort is complete.
      arg0 is true for external sort, false for internal sort.
      arg1 is the number of disk blocks used for an external sort,
      or kilobytes of memory used for an internal sort.</entry>
    </row>
    <row>
     <entry><literal>lwlock-acquire</literal></entry>
     <entry><literal>(char *, LWLockMode)</literal></entry>
     <entry>Probe that fires when an LWLock has been acquired.
      arg0 is the LWLock's tranche.
      arg1 is the requested lock mode, either exclusive or shared.</entry>
    </row>
    <row>
     <entry><literal>lwlock-release</literal></entry>
     <entry><literal>(char *)</literal></entry>
     <entry>Probe that fires when an LWLock has been released (but note
      that any released waiters have not yet been awakened).
      arg0 is the LWLock's tranche.</entry>
    </row>
    <row>
     <entry><literal>lwlock-wait-start</literal></entry>
     <entry><literal>(char *, LWLockMode)</literal></entry>
     <entry>Probe that fires when an LWLock was not immediately available and
      a server process has begun to wait for the lock to become available.
      arg0 is the LWLock's tranche.
      arg1 is the requested lock mode, either exclusive or shared.</entry>
    </row>
    <row>
     <entry><literal>lwlock-wait-done</literal></entry>
     <entry><literal>(char *, LWLockMode)</literal></entry>
     <entry>Probe that fires when a server process has been released from its
      wait for an LWLock
Title: Built-in DTrace Probes in PostgreSQL (SMGR and Sort Operations, and LWLock)
Summary
This section details DTrace probes in PostgreSQL related to SMGR (Storage Manager), sort operations, and lightweight locks (LWLock). For SMGR, probes are described that fire at the start and completion of writing a block to a relation, providing information about forks, block numbers, relation identifiers, and the backend creating the temporary relation. The probes for sort operations indicate the start and completion of a sort, differentiating between heap, index, and datum sorts, and providing details about unique value enforcement, the number of key columns, memory allowed, random access requirements, and parallel worker status. Finally, LWLock probes are described, including those for acquiring and releasing locks, and for the start and end of waiting for a lock, including the LWLock's tranche and the requested lock mode.