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Commit49d6c7d

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Add SQL function array_reverse()
This function takes in input an array, and reverses the position of allits elements. This operation only affects the first dimension of thearray, like array_shuffle().The implementation structure is inspired by array_shuffle(), with asubroutine called array_reverse_n() that may come in handy in thefuture, should more functions able to reverse portions of arrays beintroduced.Bump catalog version.Author: Aleksander AlekseevReviewed-by: Ashutosh Bapat, Tom Lane, Vladlen PopolitovDiscussion:https://postgr.es/m/CAJ7c6TMpeO_ke+QGOaAx9xdJuxa7r=49-anMh3G5476e3CX1CA@mail.gmail.com
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6 files changed

+171
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6 files changed

+171
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lines changed

‎doc/src/sgml/func.sgml

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@@ -20379,6 +20379,23 @@ SELECT NULLIF(value, '(none)') ...
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</para></entry>
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</row>
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<row>
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<entry role="func_table_entry"><para role="func_signature">
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<indexterm>
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<primary>array_reverse</primary>
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</indexterm>
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<function>array_reverse</function> ( <type>anyarray</type> )
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<returnvalue>anyarray</returnvalue>
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</para>
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<para>
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Reverses the first dimension of the array.
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</para>
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<para>
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<literal>array_reverse(ARRAY[[1,2],[3,4],[5,6]])</literal>
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<returnvalue>{{5,6},{3,4},{1,2}}</returnvalue>
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</para></entry>
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</row>
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<row>
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<entry role="func_table_entry"><para role="func_signature">
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<indexterm>

‎src/backend/utils/adt/array_userfuncs.c

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@@ -1685,3 +1685,115 @@ array_sample(PG_FUNCTION_ARGS)
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PG_RETURN_ARRAYTYPE_P(result);
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}
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/*
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* array_reverse_n
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*Return a copy of array with reversed items.
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*
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* NOTE: it would be cleaner to look up the elmlen/elmbval/elmalign info
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* from the system catalogs, given only the elmtyp. However, the caller is
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* in a better position to cache this info across multiple calls.
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*/
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staticArrayType*
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array_reverse_n(ArrayType*array,Oidelmtyp,TypeCacheEntry*typentry)
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{
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ArrayType*result;
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intndim,
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*dims,
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*lbs,
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nelm,
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nitem,
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rdims[MAXDIM],
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rlbs[MAXDIM];
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int16elmlen;
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boolelmbyval;
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charelmalign;
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Datum*elms,
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*ielms;
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bool*nuls,
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*inuls;
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ndim=ARR_NDIM(array);
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dims=ARR_DIMS(array);
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lbs=ARR_LBOUND(array);
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elmlen=typentry->typlen;
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elmbyval=typentry->typbyval;
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elmalign=typentry->typalign;
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deconstruct_array(array,elmtyp,elmlen,elmbyval,elmalign,
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&elms,&nuls,&nelm);
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nitem=dims[0];/* total number of items */
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nelm /=nitem;/* number of elements per item */
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/* Reverse the array */
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ielms=elms;
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inuls=nuls;
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for (inti=0;i<nitem /2;i++)
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{
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intj= (nitem-i-1)*nelm;
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Datum*jelms=elms+j;
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bool*jnuls=nuls+j;
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/* Swap i'th and j'th items; advance ielms/inuls to next item */
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for (intk=0;k<nelm;k++)
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{
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Datumelm=*ielms;
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boolnul=*inuls;
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*ielms++=*jelms;
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*inuls++=*jnuls;
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*jelms++=elm;
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*jnuls++=nul;
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}
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}
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/* Set up dimensions of the result */
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memcpy(rdims,dims,ndim*sizeof(int));
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memcpy(rlbs,lbs,ndim*sizeof(int));
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rdims[0]=nitem;
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result=construct_md_array(elms,nuls,ndim,rdims,rlbs,
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elmtyp,elmlen,elmbyval,elmalign);
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pfree(elms);
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pfree(nuls);
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returnresult;
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}
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/*
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* array_reverse
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*
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* Returns an array with the same dimensions as the input array, with its
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* first-dimension elements in reverse order.
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*/
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Datum
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array_reverse(PG_FUNCTION_ARGS)
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{
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ArrayType*array=PG_GETARG_ARRAYTYPE_P(0);
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ArrayType*result;
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Oidelmtyp;
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TypeCacheEntry*typentry;
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/*
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* There is no point in reversing empty arrays or arrays with less than
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* two items.
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*/
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if (ARR_NDIM(array)<1||ARR_DIMS(array)[0]<2)
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PG_RETURN_ARRAYTYPE_P(array);
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elmtyp=ARR_ELEMTYPE(array);
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typentry= (TypeCacheEntry*)fcinfo->flinfo->fn_extra;
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if (typentry==NULL||typentry->type_id!=elmtyp)
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{
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typentry=lookup_type_cache(elmtyp,0);
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fcinfo->flinfo->fn_extra= (void*)typentry;
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}
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result=array_reverse_n(array,elmtyp,typentry);
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PG_RETURN_ARRAYTYPE_P(result);
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}

‎src/include/catalog/catversion.h

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@@ -57,6 +57,6 @@
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*/
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/*yyyymmddN */
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#defineCATALOG_VERSION_NO202410311
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#defineCATALOG_VERSION_NO202411011
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#endif

‎src/include/catalog/pg_proc.dat

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@@ -1741,6 +1741,9 @@
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{ oid => '6216', descr => 'take samples from array',
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proname => 'array_sample', provolatile => 'v', prorettype => 'anyarray',
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proargtypes => 'anyarray int4', prosrc => 'array_sample' },
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{ oid => '8686', descr => 'reverse array',
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proname => 'array_reverse', prorettype => 'anyarray',
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proargtypes => 'anyarray', prosrc => 'array_reverse' },
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{ oid => '3816', descr => 'array typanalyze',
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proname => 'array_typanalyze', provolatile => 's', prorettype => 'bool',
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proargtypes => 'internal', prosrc => 'array_typanalyze' },

‎src/test/regress/expected/arrays.out

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@@ -2703,3 +2703,34 @@ SELECT array_sample('{1,2,3,4,5,6}'::int[], -1); -- fail
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ERROR: sample size must be between 0 and 6
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SELECT array_sample('{1,2,3,4,5,6}'::int[], 7); --fail
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ERROR: sample size must be between 0 and 6
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-- array_reverse
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SELECT array_reverse('{}'::int[]);
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array_reverse
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---------------
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{}
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(1 row)
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SELECT array_reverse('{1}'::int[]);
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array_reverse
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---------------
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{1}
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(1 row)
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SELECT array_reverse('{1,2}'::int[]);
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array_reverse
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---------------
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{2,1}
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(1 row)
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SELECT array_reverse('{1,2,3,NULL,4,5,6}'::int[]);
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array_reverse
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--------------------
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{6,5,4,NULL,3,2,1}
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(1 row)
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SELECT array_reverse('{{1,2},{3,4},{5,6},{7,8}}'::int[]);
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array_reverse
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---------------------------
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{{7,8},{5,6},{3,4},{1,2}}
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(1 row)
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‎src/test/regress/sql/arrays.sql

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@@ -827,3 +827,10 @@ SELECT array_dims(array_sample('[-1:2][2:3]={{1,2},{3,NULL},{5,6},{7,8}}'::int[]
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SELECT array_dims(array_sample('{{{1,2},{3,NULL}},{{5,6},{7,8}},{{9,10},{11,12}}}'::int[],2));
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SELECT array_sample('{1,2,3,4,5,6}'::int[],-1);-- fail
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SELECT array_sample('{1,2,3,4,5,6}'::int[],7);--fail
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-- array_reverse
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SELECT array_reverse('{}'::int[]);
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SELECT array_reverse('{1}'::int[]);
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SELECT array_reverse('{1,2}'::int[]);
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SELECT array_reverse('{1,2,3,NULL,4,5,6}'::int[]);
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SELECT array_reverse('{{1,2},{3,4},{5,6},{7,8}}'::int[]);

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