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Trial implementation of ALTER DROP COLUMN.
They are #ifdef'd. Add -D_DROP_COLUMN_HACK__ compile option to evaluate it.
This commit is contained in:
Hiroshi Inoue
@ -8,7 +8,7 @@
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*
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*
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* IDENTIFICATION
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* $Header: /cvsroot/pgsql/src/backend/commands/Attic/command.c,v 1.69 2000/02/15 18:15:12 tgl Exp $
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* $Header: /cvsroot/pgsql/src/backend/commands/Attic/command.c,v 1.70 2000/03/09 05:00:23 inoue Exp $
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*
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* NOTES
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* The PortalExecutorHeapMemory crap needs to be eliminated
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@ -43,6 +43,15 @@
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#include "utils/syscache.h"
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#include "utils/temprel.h"
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#include "commands/trigger.h"
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#ifdef _DROP_COLUMN_HACK__
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#include "catalog/pg_index.h"
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#include "catalog/pg_relcheck.h"
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#include "commands/defrem.h"
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#include "commands/comment.h"
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#include "access/genam.h"
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#include "optimizer/clauses.h"
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#include "../parser/parse.h"
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#endif /* _DROP_COLUMN_HACK__ */
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/* ----------------
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* PortalExecutorHeapMemory stuff
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@ -668,6 +677,213 @@ drop_default(Oid relid, int16 attnum)
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}
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#ifdef _DROP_COLUMN_HACK__
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/*
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* ALTER TABLE DROP COLUMN trial implementation
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*
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*/
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/*
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* system table scan(index scan/sequential scan)
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*/
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typedef struct SysScanDescData
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{
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Relation heap_rel;
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Relation irel;
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HeapScanDesc scan;
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IndexScanDesc iscan;
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HeapTupleData tuple;
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Buffer buffer;
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} SysScanDescData, *SysScanDesc;
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static void *
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systable_beginscan(Relation rel, const char *indexRelname, int nkeys, ScanKey entry)
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{
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bool hasindex = (rel->rd_rel->relhasindex && !IsIgnoringSystemIndexes());
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SysScanDesc sysscan;
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sysscan = (SysScanDesc) palloc(sizeof(SysScanDescData));
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sysscan->heap_rel = rel;
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sysscan->irel = (Relation) NULL;
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sysscan->tuple.t_datamcxt = NULL;
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sysscan->tuple.t_data = NULL;
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sysscan->buffer = InvalidBuffer;
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if (hasindex)
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{
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sysscan->irel = index_openr((char *)indexRelname);
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sysscan->iscan = index_beginscan(sysscan->irel, false, nkeys, entry);
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}
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else
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sysscan->scan = heap_beginscan(rel, false, SnapshotNow, nkeys, entry);
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return (void *) sysscan;
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}
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static void
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systable_endscan(void *scan)
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{
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SysScanDesc sysscan = (SysScanDesc) scan;
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if (sysscan->irel)
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{
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if (BufferIsValid(sysscan->buffer))
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ReleaseBuffer(sysscan->buffer);
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index_endscan(sysscan->iscan);
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index_close(sysscan->irel);
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}
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else
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heap_endscan(sysscan->scan);
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pfree(scan);
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}
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static HeapTuple
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systable_getnext(void *scan)
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{
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SysScanDesc sysscan = (SysScanDesc) scan;
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HeapTuple htup = (HeapTuple) NULL;
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RetrieveIndexResult indexRes;
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if (sysscan->irel)
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{
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if (BufferIsValid(sysscan->buffer))
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{
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ReleaseBuffer(sysscan->buffer);
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sysscan->buffer = InvalidBuffer;
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}
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while (indexRes = index_getnext(sysscan->iscan, ForwardScanDirection), indexRes != NULL)
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{
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sysscan->tuple.t_self = indexRes->heap_iptr;
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heap_fetch(sysscan->heap_rel, SnapshotNow, &sysscan->tuple, &(sysscan->buffer));
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pfree(indexRes);
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if (sysscan->tuple.t_data != NULL)
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{
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htup = &sysscan->tuple;
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break;
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}
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}
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}
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else
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htup = heap_getnext(sysscan->scan, 0);
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return htup;
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}
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/*
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* find a specified attribute in a node entry
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*/
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static bool
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find_attribute_walker(Node *node, int attnum)
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{
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if (node == NULL)
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return false;
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if (IsA(node, Var))
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{
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Var *var = (Var *) node;
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if (var->varlevelsup == 0 && var->varno == 1 &&
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var->varattno == attnum)
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return true;
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}
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return expression_tree_walker(node, find_attribute_walker, (void *)attnum);
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}
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static bool
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find_attribute_in_node(Node *node, int attnum)
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{
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return expression_tree_walker(node, find_attribute_walker, (void *)attnum);
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}
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/*
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* Remove/check references for the column
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*/
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static bool
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RemoveColumnReferences(Oid reloid, int attnum, bool checkonly, HeapTuple reltup)
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{
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Relation indexRelation, rcrel;
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ScanKeyData entry;
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HeapScanDesc scan;
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void *sysscan;
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HeapTuple htup, indexTuple;
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Form_pg_index index;
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Form_pg_relcheck relcheck;
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Form_pg_class pgcform = (Form_pg_class) NULL;
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int i;
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bool checkok = true;
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if (!checkonly)
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pgcform = (Form_pg_class) GETSTRUCT (reltup);
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/*
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* Remove/check constraints here
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*/
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ScanKeyEntryInitialize(&entry, (bits16) 0x0, Anum_pg_relcheck_rcrelid,
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(RegProcedure) F_OIDEQ, ObjectIdGetDatum(reloid));
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rcrel = heap_openr(RelCheckRelationName, RowExclusiveLock);
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sysscan = systable_beginscan(rcrel, RelCheckIndex,1 ,&entry);
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while (HeapTupleIsValid(htup = systable_getnext(sysscan)))
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{
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char *ccbin;
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Node *node;
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relcheck = (Form_pg_relcheck) GETSTRUCT(htup);
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ccbin = textout(&relcheck->rcbin);
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if (!ccbin)
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continue;
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node = stringToNode(ccbin);
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pfree(ccbin);
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if (find_attribute_in_node(node, attnum))
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{
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if (checkonly)
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{
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checkok = false;
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elog(ERROR, "target column is used in a constraint");
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}
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else
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{
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heap_delete(rcrel, &htup->t_self, NULL);
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pgcform->relchecks--;
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}
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}
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}
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systable_endscan(sysscan);
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heap_close(rcrel, NoLock);
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/*
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* What to do with triggers/rules/views/procedues ?
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*/
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/*
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* Remove/check indexes
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*/
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indexRelation = heap_openr(IndexRelationName, RowExclusiveLock);
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ScanKeyEntryInitialize(&entry, 0, Anum_pg_index_indrelid, F_OIDEQ,
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ObjectIdGetDatum(reloid));
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scan = heap_beginscan(indexRelation, false, SnapshotNow, 1, &entry);
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while (HeapTupleIsValid(indexTuple = heap_getnext(scan, 0)))
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{
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index = (Form_pg_index) GETSTRUCT(indexTuple);
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for (i = 0; i < INDEX_MAX_KEYS; i++)
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{
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if (index->indkey[i] == InvalidAttrNumber)
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break;
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else if (index->indkey[i] == attnum)
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{
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if (checkonly)
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{
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checkok = false;
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elog(ERROR, "target column is used in an index");
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}
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else
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{
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htup = SearchSysCacheTuple(RELOID,
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ObjectIdGetDatum(index->indexrelid),
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0, 0, 0);
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RemoveIndex(NameStr(((Form_pg_class) GETSTRUCT(htup))->relname));
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}
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break;
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}
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}
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}
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heap_endscan(scan);
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heap_close(indexRelation, NoLock);
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return checkok;
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}
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#endif /* _DROP_COLUMN_HACK__ */
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/*
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* ALTER TABLE DROP COLUMN
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@ -677,7 +893,170 @@ AlterTableDropColumn(const char *relationName,
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bool inh, const char *colName,
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int behavior)
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{
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#ifdef _DROP_COLUMN_HACK__
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Relation rel, attrdesc, adrel;
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Oid myrelid, attoid;
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HeapTuple reltup;
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HeapTupleData classtuple;
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Buffer buffer;
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Form_pg_attribute attribute;
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HeapTuple tup;
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Relation idescs[Num_pg_attr_indices];
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int attnum;
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bool hasindex;
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char dropColname[32];
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void *sysscan;
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ScanKeyData scankeys[2];
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if (inh)
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elog(ERROR, "ALTER TABLE / DROP COLUMN with inherit option is not supported yet");
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/*
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* permissions checking. this would normally be done in utility.c,
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* but this particular routine is recursive.
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*
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* normally, only the owner of a class can change its schema.
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*/
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if (!allowSystemTableMods && IsSystemRelationName(relationName))
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elog(ERROR, "ALTER TABLE: relation \"%s\" is a system catalog",
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relationName);
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#ifndef NO_SECURITY
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if (!pg_ownercheck(UserName, relationName, RELNAME))
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elog(ERROR, "ALTER TABLE: permission denied");
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#endif
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/*
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* Grab an exclusive lock on the target table, which we will NOT release
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* until end of transaction.
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*/
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rel = heap_openr(relationName, AccessExclusiveLock);
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myrelid = RelationGetRelid(rel);
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heap_close(rel, NoLock); /* close rel but keep lock! */
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/*
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* What to do when rel has inheritors ?
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*/
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if (length(find_all_inheritors(myrelid)) > 1)
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elog(ERROR, "ALTER TABLE: cannot drop a column on table that is inherited from");
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/*
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* lock the pg_class tuple for update
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*/
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reltup = SearchSysCacheTuple(RELNAME, PointerGetDatum(relationName),
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0, 0, 0);
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if (!HeapTupleIsValid(reltup))
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elog(ERROR, "ALTER TABLE: relation \"%s\" not found",
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relationName);
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rel = heap_openr(RelationRelationName, RowExclusiveLock);
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classtuple.t_self = reltup->t_self;
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switch (heap_mark4update(rel, &classtuple, &buffer))
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{
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case HeapTupleSelfUpdated:
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case HeapTupleMayBeUpdated:
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break;
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default:
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elog(ERROR, "couldn't lock pg_class tuple");
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}
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reltup = heap_copytuple(&classtuple);
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ReleaseBuffer(buffer);
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/*
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* XXX is the following check sufficient?
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*/
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if (((Form_pg_class) GETSTRUCT(reltup))->relkind != RELKIND_RELATION)
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{
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elog(ERROR, "ALTER TABLE: relation \"%s\" is not a table",
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relationName);
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}
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attrdesc = heap_openr(AttributeRelationName, RowExclusiveLock);
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/*
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* Get the target pg_attribute tuple
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*/
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tup = SearchSysCacheTupleCopy(ATTNAME,
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ObjectIdGetDatum(reltup->t_data->t_oid),
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PointerGetDatum(colName), 0, 0);
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if (!HeapTupleIsValid(tup))
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elog(ERROR, "ALTER TABLE: column name \"%s\" doesn't exist in table \"%s\"",
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colName, relationName);
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attribute = (Form_pg_attribute) GETSTRUCT(tup);
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if (attribute->attnum <= 0)
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elog(ERROR, "ALTER TABLE: column name \"%s\" was already dropped", colName);
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attnum = attribute->attnum;
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attoid = tup->t_data->t_oid;
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/*
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* Check constraints/indices etc here
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*/
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if (behavior != CASCADE)
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{
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if (!RemoveColumnReferences(myrelid, attnum, true, NULL))
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elog(ERROR, "the column is referenced");
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}
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/*
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* change the target pg_attribute tuple
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*/
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sprintf(dropColname, "*already Dropped*%d", attnum);
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namestrcpy(&(attribute->attname), dropColname);
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ATTRIBUTE_DROP_COLUMN(attribute);
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heap_update(attrdesc, &tup->t_self, tup, NULL);
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hasindex = (!IsIgnoringSystemIndexes() && RelationGetForm(attrdesc)->relhasindex);
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if (hasindex)
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{
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CatalogOpenIndices(Num_pg_attr_indices, Name_pg_attr_indices, idescs);
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CatalogIndexInsert(idescs, Num_pg_attr_indices,
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attrdesc, tup);
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CatalogCloseIndices(Num_pg_attr_indices, idescs);
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}
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heap_close(attrdesc, NoLock);
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heap_freetuple(tup);
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/* delete comments */
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DeleteComments(attoid);
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/* delete attrdef */
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adrel = heap_openr(AttrDefaultRelationName, RowExclusiveLock);
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ScanKeyEntryInitialize(&scankeys[0], 0x0, Anum_pg_attrdef_adrelid,
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F_OIDEQ, ObjectIdGetDatum(myrelid));
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/* Oops pg_attrdef doesn't have (adrelid,adnum) index
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ScanKeyEntryInitialize(&scankeys[1], 0x0, Anum_pg_attrdef_adnum,
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F_INT2EQ, Int16GetDatum(attnum));
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sysscan = systable_beginscan(adrel, AttrDefaultIndex, 2, scankeys);
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*/
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sysscan = systable_beginscan(adrel, AttrDefaultIndex, 1, scankeys);
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while (HeapTupleIsValid(tup = systable_getnext(sysscan)))
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{
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if (((Form_pg_attrdef) GETSTRUCT(tup))->adnum == attnum)
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{
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heap_delete(adrel, &tup->t_self, NULL);
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break;
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}
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}
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systable_endscan(sysscan);
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heap_close(adrel, NoLock);
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/*
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* Remove objects which reference this column
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*/
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if (behavior == CASCADE)
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{
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Relation ridescs[Num_pg_class_indices];
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RemoveColumnReferences(myrelid, attnum, false, reltup);
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/* update pg_class tuple */
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heap_update(rel, &reltup->t_self, reltup, NULL);
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CatalogOpenIndices(Num_pg_class_indices, Name_pg_class_indices, ridescs);
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CatalogIndexInsert(ridescs, Num_pg_class_indices, rel, reltup);
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CatalogCloseIndices(Num_pg_class_indices, ridescs);
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}
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heap_freetuple(reltup);
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heap_close(rel, NoLock);
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#else
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elog(ERROR, "ALTER TABLE / DROP COLUMN is not implemented");
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#endif /* _DROP_COLUMN_HACK__ */
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}
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