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Commitc8b06bb

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Introduce pg_sequence_read_tuple().
This new function returns the data for the given sequence, i.e.,the values within the sequence tuple. Since this function is asubstitute for SELECT from the sequence, the SELECT privilege isrequired on the sequence in question. It returns all NULLs forsequences for which we lack privileges, other sessions' temporarysequences, and unlogged sequences on standbys.This function is primarily intended for use by pg_dump in afollow-up commit that will use it to optimize dumpSequenceData().Like pg_sequence_last_value(), which is a support function for thepg_sequences system view, pg_sequence_read_tuple() is leftundocumented.Bumps catversion.Reviewed-by: Michael Paquier, Tom LaneDiscussion:https://postgr.es/m/20240503025140.GA1227404%40nathanxps13
1 parent68e9629 commitc8b06bb

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5 files changed

+78
-1
lines changed

5 files changed

+78
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lines changed

‎src/backend/commands/sequence.c‎

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Original file line numberDiff line numberDiff line change
@@ -1773,6 +1773,67 @@ pg_sequence_parameters(PG_FUNCTION_ARGS)
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returnHeapTupleGetDatum(heap_form_tuple(tupdesc,values,isnull));
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}
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/*
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* Return the sequence tuple.
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*
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* This is primarily intended for use by pg_dump to gather sequence data
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* without needing to individually query each sequence relation.
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*/
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Datum
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pg_sequence_read_tuple(PG_FUNCTION_ARGS)
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{
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Oidrelid=PG_GETARG_OID(0);
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SeqTableelm;
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Relationseqrel;
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Datumvalues[SEQ_COL_LASTCOL]= {0};
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boolisnull[SEQ_COL_LASTCOL]= {0};
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TupleDescresultTupleDesc;
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HeapTupleresultHeapTuple;
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Datumresult;
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resultTupleDesc=CreateTemplateTupleDesc(SEQ_COL_LASTCOL);
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TupleDescInitEntry(resultTupleDesc, (AttrNumber)1,"last_value",
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INT8OID,-1,0);
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TupleDescInitEntry(resultTupleDesc, (AttrNumber)2,"log_cnt",
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INT8OID,-1,0);
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TupleDescInitEntry(resultTupleDesc, (AttrNumber)3,"is_called",
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BOOLOID,-1,0);
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resultTupleDesc=BlessTupleDesc(resultTupleDesc);
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init_sequence(relid,&elm,&seqrel);
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/*
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* Return all NULLs for sequences for which we lack privileges, other
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* sessions' temporary sequences, and unlogged sequences on standbys.
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*/
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if (pg_class_aclcheck(relid,GetUserId(),ACL_SELECT)==ACLCHECK_OK&&
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!RELATION_IS_OTHER_TEMP(seqrel)&&
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(RelationIsPermanent(seqrel)|| !RecoveryInProgress()))
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{
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Bufferbuf;
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HeapTupleDataseqtuple;
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Form_pg_sequence_dataseq;
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seq=read_seq_tuple(seqrel,&buf,&seqtuple);
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values[0]=Int64GetDatum(seq->last_value);
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values[1]=Int64GetDatum(seq->log_cnt);
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values[2]=BoolGetDatum(seq->is_called);
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UnlockReleaseBuffer(buf);
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}
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else
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memset(isnull, true,sizeof(isnull));
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sequence_close(seqrel,NoLock);
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resultHeapTuple=heap_form_tuple(resultTupleDesc,values,isnull);
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result=HeapTupleGetDatum(resultHeapTuple);
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PG_RETURN_DATUM(result);
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}
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/*
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* Return the last value from the sequence
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*

‎src/include/catalog/catversion.h‎

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -57,6 +57,6 @@
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*/
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/*yyyymmddN */
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#defineCATALOG_VERSION_NO202407252
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#defineCATALOG_VERSION_NO202407311
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#endif

‎src/include/catalog/pg_proc.dat‎

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@@ -3329,6 +3329,12 @@
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proname => 'pg_sequence_last_value', provolatile => 'v', proparallel => 'u',
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prorettype => 'int8', proargtypes => 'regclass',
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prosrc => 'pg_sequence_last_value' },
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{ oid => '9876', descr => 'return sequence tuple, for use by pg_dump',
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proname => 'pg_sequence_read_tuple', provolatile => 'v', proparallel => 'u',
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prorettype => 'record', proargtypes => 'regclass',
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proallargtypes => '{regclass,int8,int8,bool}', proargmodes => '{i,o,o,o}',
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proargnames => '{sequence_oid,last_value,log_cnt,is_called}',
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prosrc => 'pg_sequence_read_tuple' },
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{ oid => '275', descr => 'return the next oid for a system table',
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proname => 'pg_nextoid', provolatile => 'v', proparallel => 'u',

‎src/test/regress/expected/sequence.out‎

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Original file line numberDiff line numberDiff line change
@@ -839,4 +839,11 @@ SELECT nextval('test_seq1');
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3
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(1 row)
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-- pg_sequence_read_tuple
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SELECT * FROM pg_sequence_read_tuple('test_seq1');
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last_value | log_cnt | is_called
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------------+---------+-----------
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10 | 32 | t
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(1 row)
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DROP SEQUENCE test_seq1;

‎src/test/regress/sql/sequence.sql‎

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Original file line numberDiff line numberDiff line change
@@ -413,4 +413,7 @@ SELECT nextval('test_seq1');
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SELECT nextval('test_seq1');
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SELECT nextval('test_seq1');
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-- pg_sequence_read_tuple
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SELECT*FROM pg_sequence_read_tuple('test_seq1');
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DROPSEQUENCE test_seq1;

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