I did some light editing to prepare this for commit. -- Nathan Bossart Amazon Web Services: https://aws.amazon.com
>From 38c78bd92a7b4d4600e6f0dbe58283c21ea87d50 Mon Sep 17 00:00:00 2001 From: Nathan Bossart <nat...@postgresql.org> Date: Tue, 12 Mar 2024 22:04:25 -0500 Subject: [PATCH v10 1/1] Add pg_column_toast_chunk_id().
This function returns the chunk_id of an on-disk TOASTed value, or NULL if the value is un-TOASTed or not on-disk. This is useful for identifying which values are actually TOASTed and for investigating "unexpected chunk number" errors. XXX: REQUIRES CATVERSION BUMP Author: Yugo Nagata Reviewed-by: Jian He Discussion: https://postgr.es/m/20230329105507.d764497456eeac1ca491b5bd%40sraoss.co.jp --- doc/src/sgml/func.sgml | 17 ++++++++ src/backend/utils/adt/varlena.c | 41 ++++++++++++++++++++ src/include/catalog/pg_proc.dat | 3 ++ src/test/regress/expected/misc_functions.out | 16 ++++++++ src/test/regress/sql/misc_functions.sql | 12 ++++++ 5 files changed, 89 insertions(+) diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml index 0bb7aeb40e..fe9c1a38b9 100644 --- a/doc/src/sgml/func.sgml +++ b/doc/src/sgml/func.sgml @@ -28552,6 +28552,23 @@ postgres=# SELECT '0/0'::pg_lsn + pd.segment_number * ps.setting::int + :offset </para></entry> </row> + <row> + <entry role="func_table_entry"><para role="func_signature"> + <indexterm> + <primary>pg_column_toast_chunk_id</primary> + </indexterm> + <function>pg_column_toast_chunk_id</function> ( <type>"any"</type> ) + <returnvalue>oid</returnvalue> + </para> + <para> + Shows the <structfield>chunk_id</structfield> of an on-disk + <acronym>TOAST</acronym>ed value. Returns <literal>NULL</literal> + if the value is un-<acronym>TOAST</acronym>ed or not on-disk. See + <xref linkend="storage-toast"/> for more information about + <acronym>TOAST</acronym>. + </para></entry> + </row> + <row> <entry role="func_table_entry"><para role="func_signature"> <indexterm> diff --git a/src/backend/utils/adt/varlena.c b/src/backend/utils/adt/varlena.c index 543afb66e5..8d28dd42ce 100644 --- a/src/backend/utils/adt/varlena.c +++ b/src/backend/utils/adt/varlena.c @@ -5105,6 +5105,47 @@ pg_column_compression(PG_FUNCTION_ARGS) PG_RETURN_TEXT_P(cstring_to_text(result)); } +/* + * Return the chunk_id of the on-disk TOASTed value. Return NULL if the value + * is un-TOASTed or not on-disk. + */ +Datum +pg_column_toast_chunk_id(PG_FUNCTION_ARGS) +{ + int typlen; + struct varlena *attr; + struct varatt_external toast_pointer; + + /* On first call, get the input type's typlen, and save at *fn_extra */ + if (fcinfo->flinfo->fn_extra == NULL) + { + /* Lookup the datatype of the supplied argument */ + Oid argtypeid = get_fn_expr_argtype(fcinfo->flinfo, 0); + + typlen = get_typlen(argtypeid); + if (typlen == 0) /* should not happen */ + elog(ERROR, "cache lookup failed for type %u", argtypeid); + + fcinfo->flinfo->fn_extra = MemoryContextAlloc(fcinfo->flinfo->fn_mcxt, + sizeof(int)); + *((int *) fcinfo->flinfo->fn_extra) = typlen; + } + else + typlen = *((int *) fcinfo->flinfo->fn_extra); + + if (typlen != -1) + PG_RETURN_NULL(); + + attr = (struct varlena *) DatumGetPointer(PG_GETARG_DATUM(0)); + + if (!VARATT_IS_EXTERNAL_ONDISK(attr)) + PG_RETURN_NULL(); + + VARATT_EXTERNAL_GET_POINTER(toast_pointer, attr); + + PG_RETURN_OID(toast_pointer.va_valueid); +} + /* * string_agg - Concatenates values and returns string. * diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat index 291ed876fc..443ca854a6 100644 --- a/src/include/catalog/pg_proc.dat +++ b/src/include/catalog/pg_proc.dat @@ -7447,6 +7447,9 @@ { oid => '2121', descr => 'compression method for the compressed datum', proname => 'pg_column_compression', provolatile => 's', prorettype => 'text', proargtypes => 'any', prosrc => 'pg_column_compression' }, +{ oid => '8393', descr => 'chunk ID of on-disk TOASTed value', + proname => 'pg_column_toast_chunk_id', provolatile => 's', prorettype => 'oid', + proargtypes => 'any', prosrc => 'pg_column_toast_chunk_id' }, { oid => '2322', descr => 'total disk space usage for the specified tablespace', proname => 'pg_tablespace_size', provolatile => 'v', prorettype => 'int8', diff --git a/src/test/regress/expected/misc_functions.out b/src/test/regress/expected/misc_functions.out index d5f61dfad9..e0ba9fdafa 100644 --- a/src/test/regress/expected/misc_functions.out +++ b/src/test/regress/expected/misc_functions.out @@ -703,3 +703,19 @@ SELECT has_function_privilege('regress_current_logfile', (1 row) DROP ROLE regress_current_logfile; +-- pg_column_toast_chunk_id +CREATE TABLE test_chunk_id (a TEXT, b TEXT STORAGE EXTERNAL); +INSERT INTO test_chunk_id VALUES ('x', repeat('x', 8192)); +SELECT t.relname AS toastrel FROM pg_class c + LEFT JOIN pg_class t ON c.reltoastrelid = t.oid + WHERE c.relname = 'test_chunk_id' +\gset +SELECT pg_column_toast_chunk_id(a) IS NULL, + pg_column_toast_chunk_id(b) IN (SELECT chunk_id FROM pg_toast.:toastrel) + FROM test_chunk_id; + ?column? | ?column? +----------+---------- + t | t +(1 row) + +DROP TABLE test_chunk_id; diff --git a/src/test/regress/sql/misc_functions.sql b/src/test/regress/sql/misc_functions.sql index 928b04db7f..ff5ed5edde 100644 --- a/src/test/regress/sql/misc_functions.sql +++ b/src/test/regress/sql/misc_functions.sql @@ -265,3 +265,15 @@ GRANT pg_monitor TO regress_current_logfile; SELECT has_function_privilege('regress_current_logfile', 'pg_current_logfile()', 'EXECUTE'); DROP ROLE regress_current_logfile; + +-- pg_column_toast_chunk_id +CREATE TABLE test_chunk_id (a TEXT, b TEXT STORAGE EXTERNAL); +INSERT INTO test_chunk_id VALUES ('x', repeat('x', 8192)); +SELECT t.relname AS toastrel FROM pg_class c + LEFT JOIN pg_class t ON c.reltoastrelid = t.oid + WHERE c.relname = 'test_chunk_id' +\gset +SELECT pg_column_toast_chunk_id(a) IS NULL, + pg_column_toast_chunk_id(b) IN (SELECT chunk_id FROM pg_toast.:toastrel) + FROM test_chunk_id; +DROP TABLE test_chunk_id; -- 2.25.1
