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Add pg_sequences view 

Like pg_tables, pg_views, and others, this view contains information
about sequences in a way that is independent of the system catalog
layout but more comprehensive than the information schema.

To help implement the view, add a new internal function
pg_sequence_last_value() to return the last value of a sequence.  This
is kept separate from pg_sequence_parameters() to separate querying
run-time state from catalog-like information.

Reviewed-by: Andreas Karlsson <andreas@proxel.se>
This commit is contained in:
Peter Eisentraut 2016-11-18 12:00:00 -05:00
parent 8f91f323b4
commit 67dc4ccbb2
10 changed files with 233 additions and 10 deletions
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97
doc/src/sgml/catalogs.sgml
View File

@ -7394,6 +7394,11 @@
<entry>security labels</entry>
</row>
<row>
<entry><link linkend="view-pg-sequences"><structname>pg_sequences</structname></link></entry>
<entry>sequences</entry>
</row>
<row>
<entry><link linkend="view-pg-settings"><structname>pg_settings</structname></link></entry>
<entry>parameter settings</entry>
@ -9135,6 +9140,98 @@ SELECT * FROM pg_locks pl LEFT JOIN pg_prepared_xacts ppx
</table>
</sect1>
<sect1 id="view-pg-sequences">
<title><structname>pg_sequences</structname></title>
<indexterm zone="view-pg-sequences">
<primary>pg_sequences</primary>
</indexterm>
<para>
The view <structname>pg_sequences</structname> provides access to
useful information about each sequence in the database.
</para>
<table>
<title><structname>pg_sequences</> Columns</title>
<tgroup cols="4">
<thead>
<row>
<entry>Name</entry>
<entry>Type</entry>
<entry>References</entry>
<entry>Description</entry>
</row>
</thead>
<tbody>
<row>
<entry><structfield>schemaname</structfield></entry>
<entry><type>name</type></entry>
<entry><literal><link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link>.nspname</literal></entry>
<entry>Name of schema containing sequence</entry>
</row>
<row>
<entry><structfield>sequencename</structfield></entry>
<entry><type>name</type></entry>
<entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.relname</literal></entry>
<entry>Name of sequence</entry>
</row>
<row>
<entry><structfield>sequenceowner</structfield></entry>
<entry><type>name</type></entry>
<entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.rolname</literal></entry>
<entry>Name of sequence's owner</entry>
</row>
<row>
<entry><structfield>start_value</structfield></entry>
<entry><type>bigint</type></entry>
<entry></entry>
<entry>Start value of the sequence</entry>
</row>
<row>
<entry><structfield>min_value</structfield></entry>
<entry><type>bigint</type></entry>
<entry></entry>
<entry>Minimum value of the sequence</entry>
</row>
<row>
<entry><structfield>max_value</structfield></entry>
<entry><type>bigint</type></entry>
<entry></entry>
<entry>Maximum value of the sequence</entry>
</row>
<row>
<entry><structfield>increment_by</structfield></entry>
<entry><type>bigint</type></entry>
<entry></entry>
<entry>Increment value of the sequence</entry>
</row>
<row>
<entry><structfield>cycle</structfield></entry>
<entry><type>boolean</type></entry>
<entry></entry>
<entry>Whether the sequence cycles</entry>
</row>
<row>
<entry><structfield>cache_size</structfield></entry>
<entry><type>bigint</type></entry>
<entry></entry>
<entry>Cache size of the sequence</entry>
</row>
<row>
<entry><structfield>last_value</structfield></entry>
<entry><type>bigint</type></entry>
<entry></entry>
<entry>The last sequence value written to disk. If caching is used,
this value can be greater than the last value handed out from the
sequence. Null if the sequence has not been read from yet.</entry>
</row>
</tbody>
</tgroup>
</table>
</sect1>
<sect1 id="view-pg-settings">
<title><structname>pg_settings</structname></title>

17
src/backend/catalog/system_views.sql
View File

@ -158,6 +158,23 @@ CREATE VIEW pg_indexes AS
LEFT JOIN pg_tablespace T ON (T.oid = I.reltablespace)
WHERE C.relkind IN ('r', 'm') AND I.relkind = 'i';
CREATE OR REPLACE VIEW pg_sequences AS
SELECT
N.nspname AS schemaname,
C.relname AS sequencename,
pg_get_userbyid(C.relowner) AS sequenceowner,
p.start_value AS start_value,
p.minimum_value AS min_value,
p.maximum_value AS max_value,
p.increment AS increment_by,
p.cycle_option AS cycle,
p.cache_size AS cache_size,
pg_sequence_last_value(C.oid) AS last_value
FROM pg_class C LEFT JOIN pg_namespace N ON (N.oid = C.relnamespace),
LATERAL pg_sequence_parameters(C.oid) p
WHERE NOT pg_is_other_temp_schema(N.oid)
AND relkind = 'S';
CREATE VIEW pg_stats WITH (security_barrier) AS
SELECT
nspname AS schemaname,

49
src/backend/commands/sequence.c
View File

@ -1534,8 +1534,8 @@ pg_sequence_parameters(PG_FUNCTION_ARGS)
{
Oid relid = PG_GETARG_OID(0);
TupleDesc tupdesc;
Datum values[5];
bool isnull[5];
Datum values[6];
bool isnull[6];
SeqTable elm;
Relation seqrel;
Buffer buf;
@ -1551,7 +1551,7 @@ pg_sequence_parameters(PG_FUNCTION_ARGS)
errmsg("permission denied for sequence %s",
RelationGetRelationName(seqrel))));
tupdesc = CreateTemplateTupleDesc(5, false);
tupdesc = CreateTemplateTupleDesc(6, false);
TupleDescInitEntry(tupdesc, (AttrNumber) 1, "start_value",
INT8OID, -1, 0);
TupleDescInitEntry(tupdesc, (AttrNumber) 2, "minimum_value",
@ -1562,6 +1562,8 @@ pg_sequence_parameters(PG_FUNCTION_ARGS)
INT8OID, -1, 0);
TupleDescInitEntry(tupdesc, (AttrNumber) 5, "cycle_option",
BOOLOID, -1, 0);
TupleDescInitEntry(tupdesc, (AttrNumber) 6, "cache_size",
INT8OID, -1, 0);
BlessTupleDesc(tupdesc);
@ -1574,6 +1576,7 @@ pg_sequence_parameters(PG_FUNCTION_ARGS)
values[2] = Int64GetDatum(seq->max_value);
values[3] = Int64GetDatum(seq->increment_by);
values[4] = BoolGetDatum(seq->is_cycled);
values[5] = Int64GetDatum(seq->cache_value);
UnlockReleaseBuffer(buf);
relation_close(seqrel, NoLock);
@ -1581,6 +1584,46 @@ pg_sequence_parameters(PG_FUNCTION_ARGS)
return HeapTupleGetDatum(heap_form_tuple(tupdesc, values, isnull));
}
/*
* Return the last value from the sequence
*
* Note: This has a completely different meaning than lastval().
*/
Datum
pg_sequence_last_value(PG_FUNCTION_ARGS)
{
Oid relid = PG_GETARG_OID(0);
SeqTable elm;
Relation seqrel;
Buffer buf;
HeapTupleData seqtuple;
Form_pg_sequence seq;
bool is_called;
int64 result;
/* open and AccessShareLock sequence */
init_sequence(relid, &elm, &seqrel);
if (pg_class_aclcheck(relid, GetUserId(), ACL_SELECT | ACL_USAGE) != ACLCHECK_OK)
ereport(ERROR,
(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
errmsg("permission denied for sequence %s",
RelationGetRelationName(seqrel))));
seq = read_seq_tuple(elm, seqrel, &buf, &seqtuple);
is_called = seq->is_called;
result = seq->last_value;
UnlockReleaseBuffer(buf);
relation_close(seqrel, NoLock);
if (is_called)
PG_RETURN_INT64(result);
else
PG_RETURN_NULL();
}
void
seq_redo(XLogReaderState *record)

2
src/include/catalog/catversion.h
View File

@ -53,6 +53,6 @@
*/
/* yyyymmddN */
#define CATALOG_VERSION_NO 201611041
#define CATALOG_VERSION_NO 201611181
#endif

4
src/include/catalog/pg_proc.h
View File

@ -1763,8 +1763,10 @@ DATA(insert OID = 1576 ( setval PGNSP PGUID 12 1 0 0 0 f f f f t f v u 2 0 20
DESCR("set sequence value");
DATA(insert OID = 1765 ( setval PGNSP PGUID 12 1 0 0 0 f f f f t f v u 3 0 20 "2205 20 16" _null_ _null_ _null_ _null_ _null_ setval3_oid _null_ _null_ _null_ ));
DESCR("set sequence value and is_called status");
DATA(insert OID = 3078 ( pg_sequence_parameters PGNSP PGUID 12 1 0 0 0 f f f f t f s s 1 0 2249 "26" "{26,20,20,20,20,16}" "{i,o,o,o,o,o}" "{sequence_oid,start_value,minimum_value,maximum_value,increment,cycle_option}" _null_ _null_ pg_sequence_parameters _null_ _null_ _null_));
DATA(insert OID = 3078 ( pg_sequence_parameters PGNSP PGUID 12 1 0 0 0 f f f f t f s s 1 0 2249 "26" "{26,20,20,20,20,16,20}" "{i,o,o,o,o,o,o}" "{sequence_oid,start_value,minimum_value,maximum_value,increment,cycle_option,cache_size}" _null_ _null_ pg_sequence_parameters _null_ _null_ _null_));
DESCR("sequence parameters, for use by information schema");
DATA(insert OID = 4032 ( pg_sequence_last_value PGNSP PGUID 12 1 0 0 0 f f f f t f v u 1 0 20 "2205" _null_ _null_ _null_ _null_ _null_ pg_sequence_last_value _null_ _null_ _null_ ));
DESCR("sequence last value");
DATA(insert OID = 1579 ( varbit_in PGNSP PGUID 12 1 0 0 0 f f f f t f i s 3 0 1562 "2275 26 23" _null_ _null_ _null_ _null_ _null_ varbit_in _null_ _null_ _null_ ));
DESCR("I/O");

1
src/include/commands/sequence.h
View File

@ -73,6 +73,7 @@ extern Datum setval3_oid(PG_FUNCTION_ARGS);
extern Datum lastval(PG_FUNCTION_ARGS);
extern Datum pg_sequence_parameters(PG_FUNCTION_ARGS);
extern Datum pg_sequence_last_value(PG_FUNCTION_ARGS);
extern ObjectAddress DefineSequence(ParseState *pstate, CreateSeqStmt *stmt);
extern ObjectAddress AlterSequence(ParseState *pstate, AlterSeqStmt *stmt);

14
src/test/regress/expected/rules.out
View File

@ -1615,6 +1615,20 @@ UNION ALL
l.label
FROM (pg_shseclabel l
JOIN pg_authid rol ON (((l.classoid = rol.tableoid) AND (l.objoid = rol.oid))));
pg_sequences| SELECT n.nspname AS schemaname,
c.relname AS sequencename,
pg_get_userbyid(c.relowner) AS sequenceowner,
p.start_value,
p.minimum_value AS min_value,
p.maximum_value AS max_value,
p.increment AS increment_by,
p.cycle_option AS cycle,
p.cache_size,
pg_sequence_last_value((c.oid)::regclass) AS last_value
FROM (pg_class c
LEFT JOIN pg_namespace n ON ((n.oid = c.relnamespace))),
LATERAL pg_sequence_parameters(c.oid) p(start_value, minimum_value, maximum_value, increment, cycle_option, cache_size)
WHERE ((NOT pg_is_other_temp_schema(n.oid)) AND (c.relkind = 'S'::"char"));
pg_settings| SELECT a.name,
a.setting,
a.unit,

23
src/test/regress/expected/sequence.out
View File

@ -300,20 +300,39 @@ SELECT nextval('sequence_test2');
5
(1 row)
CREATE SEQUENCE sequence_test3; -- not read from, to test is_called
-- Information schema
SELECT * FROM information_schema.sequences WHERE sequence_name IN
('sequence_test2', 'serialtest2_f2_seq', 'serialtest2_f3_seq',
('sequence_test2', 'sequence_test3', 'serialtest2_f2_seq', 'serialtest2_f3_seq',
'serialtest2_f4_seq', 'serialtest2_f5_seq', 'serialtest2_f6_seq')
ORDER BY sequence_name ASC;
sequence_catalog | sequence_schema | sequence_name | data_type | numeric_precision | numeric_precision_radix | numeric_scale | start_value | minimum_value | maximum_value | increment | cycle_option
------------------+-----------------+--------------------+-----------+-------------------+-------------------------+---------------+-------------+---------------+---------------------+-----------+--------------
regression | public | sequence_test2 | bigint | 64 | 2 | 0 | 32 | 5 | 36 | 4 | YES
regression | public | sequence_test3 | bigint | 64 | 2 | 0 | 1 | 1 | 9223372036854775807 | 1 | NO
regression | public | serialtest2_f2_seq | bigint | 64 | 2 | 0 | 1 | 1 | 9223372036854775807 | 1 | NO
regression | public | serialtest2_f3_seq | bigint | 64 | 2 | 0 | 1 | 1 | 9223372036854775807 | 1 | NO
regression | public | serialtest2_f4_seq | bigint | 64 | 2 | 0 | 1 | 1 | 9223372036854775807 | 1 | NO
regression | public | serialtest2_f5_seq | bigint | 64 | 2 | 0 | 1 | 1 | 9223372036854775807 | 1 | NO
regression | public | serialtest2_f6_seq | bigint | 64 | 2 | 0 | 1 | 1 | 9223372036854775807 | 1 | NO
(6 rows)
(7 rows)
SELECT schemaname, sequencename, start_value, min_value, max_value, increment_by, cycle, cache_size, last_value
FROM pg_sequences
WHERE sequencename IN
('sequence_test2', 'sequence_test3', 'serialtest2_f2_seq', 'serialtest2_f3_seq',
'serialtest2_f4_seq', 'serialtest2_f5_seq', 'serialtest2_f6_seq')
ORDER BY sequencename ASC;
schemaname | sequencename | start_value | min_value | max_value | increment_by | cycle | cache_size | last_value
------------+--------------------+-------------+-----------+---------------------+--------------+-------+------------+------------
public | sequence_test2 | 32 | 5 | 36 | 4 | t | 1 | 5
public | sequence_test3 | 1 | 1 | 9223372036854775807 | 1 | f | 1 |
public | serialtest2_f2_seq | 1 | 1 | 9223372036854775807 | 1 | f | 1 | 2
public | serialtest2_f3_seq | 1 | 1 | 9223372036854775807 | 1 | f | 1 | 2
public | serialtest2_f4_seq | 1 | 1 | 9223372036854775807 | 1 | f | 1 | 2
public | serialtest2_f5_seq | 1 | 1 | 9223372036854775807 | 1 | f | 1 | 2
public | serialtest2_f6_seq | 1 | 1 | 9223372036854775807 | 1 | f | 1 | 2
(7 rows)
-- Test comments
COMMENT ON SEQUENCE asdf IS 'won''t work';

23
src/test/regress/expected/sequence_1.out
View File

@ -300,20 +300,39 @@ SELECT nextval('sequence_test2');
5
(1 row)
CREATE SEQUENCE sequence_test3; -- not read from, to test is_called
-- Information schema
SELECT * FROM information_schema.sequences WHERE sequence_name IN
('sequence_test2', 'serialtest2_f2_seq', 'serialtest2_f3_seq',
('sequence_test2', 'sequence_test3', 'serialtest2_f2_seq', 'serialtest2_f3_seq',
'serialtest2_f4_seq', 'serialtest2_f5_seq', 'serialtest2_f6_seq')
ORDER BY sequence_name ASC;
sequence_catalog | sequence_schema | sequence_name | data_type | numeric_precision | numeric_precision_radix | numeric_scale | start_value | minimum_value | maximum_value | increment | cycle_option
------------------+-----------------+--------------------+-----------+-------------------+-------------------------+---------------+-------------+---------------+---------------------+-----------+--------------
regression | public | sequence_test2 | bigint | 64 | 2 | 0 | 32 | 5 | 36 | 4 | YES
regression | public | sequence_test3 | bigint | 64 | 2 | 0 | 1 | 1 | 9223372036854775807 | 1 | NO
regression | public | serialtest2_f2_seq | bigint | 64 | 2 | 0 | 1 | 1 | 9223372036854775807 | 1 | NO
regression | public | serialtest2_f3_seq | bigint | 64 | 2 | 0 | 1 | 1 | 9223372036854775807 | 1 | NO
regression | public | serialtest2_f4_seq | bigint | 64 | 2 | 0 | 1 | 1 | 9223372036854775807 | 1 | NO
regression | public | serialtest2_f5_seq | bigint | 64 | 2 | 0 | 1 | 1 | 9223372036854775807 | 1 | NO
regression | public | serialtest2_f6_seq | bigint | 64 | 2 | 0 | 1 | 1 | 9223372036854775807 | 1 | NO
(6 rows)
(7 rows)
SELECT schemaname, sequencename, start_value, min_value, max_value, increment_by, cycle, cache_size, last_value
FROM pg_sequences
WHERE sequencename IN
('sequence_test2', 'sequence_test3', 'serialtest2_f2_seq', 'serialtest2_f3_seq',
'serialtest2_f4_seq', 'serialtest2_f5_seq', 'serialtest2_f6_seq')
ORDER BY sequencename ASC;
schemaname | sequencename | start_value | min_value | max_value | increment_by | cycle | cache_size | last_value
------------+--------------------+-------------+-----------+---------------------+--------------+-------+------------+------------
public | sequence_test2 | 32 | 5 | 36 | 4 | t | 1 | 5
public | sequence_test3 | 1 | 1 | 9223372036854775807 | 1 | f | 1 |
public | serialtest2_f2_seq | 1 | 1 | 9223372036854775807 | 1 | f | 1 | 2
public | serialtest2_f3_seq | 1 | 1 | 9223372036854775807 | 1 | f | 1 | 2
public | serialtest2_f4_seq | 1 | 1 | 9223372036854775807 | 1 | f | 1 | 2
public | serialtest2_f5_seq | 1 | 1 | 9223372036854775807 | 1 | f | 1 | 2
public | serialtest2_f6_seq | 1 | 1 | 9223372036854775807 | 1 | f | 1 | 2
(7 rows)
-- Test comments
COMMENT ON SEQUENCE asdf IS 'won''t work';

13
src/test/regress/sql/sequence.sql
View File

@ -138,12 +138,23 @@ SELECT nextval('sequence_test2');
SELECT nextval('sequence_test2');
SELECT nextval('sequence_test2');
CREATE SEQUENCE sequence_test3; -- not read from, to test is_called
-- Information schema
SELECT * FROM information_schema.sequences WHERE sequence_name IN
('sequence_test2', 'serialtest2_f2_seq', 'serialtest2_f3_seq',
('sequence_test2', 'sequence_test3', 'serialtest2_f2_seq', 'serialtest2_f3_seq',
'serialtest2_f4_seq', 'serialtest2_f5_seq', 'serialtest2_f6_seq')
ORDER BY sequence_name ASC;
SELECT schemaname, sequencename, start_value, min_value, max_value, increment_by, cycle, cache_size, last_value
FROM pg_sequences
WHERE sequencename IN
('sequence_test2', 'sequence_test3', 'serialtest2_f2_seq', 'serialtest2_f3_seq',
'serialtest2_f4_seq', 'serialtest2_f5_seq', 'serialtest2_f6_seq')
ORDER BY sequencename ASC;
-- Test comments
COMMENT ON SEQUENCE asdf IS 'won''t work';
COMMENT ON SEQUENCE sequence_test2 IS 'will work';