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Commite1551f9

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committed
Refactor attribute mappings used in logical tuple conversion
Tuple conversion support in tupconvert.c is able to convert rowtypesbetween two relations, inner and outer, which are logically equivalentbut have a different ordering or even dropped columns (used mainly forinheritance tree and partitions). This makes use of attribute mappings,which are simple arrays made of AttrNumber elements with a lengthmatching the number of attributes of the outer relation. The length ofthe attribute mapping has been treated as completely independent of themapping itself until now, making it easy to pass down an incorrectmapping length.This commit refactors the code related to attribute mappings and movesit into an independent facility called attmap.c, extracted fromtupconvert.c. This merges the attribute mapping with its length,avoiding to try to guess what is the length of a mapping to use as thisis computed once, when the map is built.This will avoid mistakes like what has been fixed indc816e5, which hasused an incorrect mapping length by matching it with the number ofattributes of an inner relation (a child partition) instead of an outerrelation (a partitioned table).Author: Michael PaquierReviewed-by: Amit LangoteDiscussion:https://postgr.es/m/20191121042556.GD153437@paquier.xyz
1 parent04c8a69 commite1551f9

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22 files changed

+533
-419
lines changed

22 files changed

+533
-419
lines changed

‎src/backend/access/common/Makefile

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Original file line numberDiff line numberDiff line change
@@ -13,6 +13,7 @@ top_builddir = ../../../..
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include$(top_builddir)/src/Makefile.global
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OBJS =\
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attmap.o\
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bufmask.o\
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detoast.o\
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heaptuple.o\

‎src/backend/access/common/attmap.c

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/*-------------------------------------------------------------------------
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*
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* attmap.c
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* Attribute mapping support.
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*
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* This file provides utility routines to build and manage attribute
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* mappings by comparing input and output TupleDescs. Such mappings
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* are typically used by DDL operating on inheritance and partition trees
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* to do a conversion between rowtypes logically equivalent but with
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* columns in a different order, taking into account dropped columns.
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* They are also used by the tuple conversion routines in tupconvert.c.
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*
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* Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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*
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* IDENTIFICATION
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* src/backend/access/common/attmap.c
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*
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*-------------------------------------------------------------------------
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*/
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#include"postgres.h"
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#include"access/attmap.h"
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#include"access/htup_details.h"
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#include"utils/builtins.h"
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staticboolcheck_attrmap_match(TupleDescindesc,
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TupleDescoutdesc,
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AttrMap*attrMap);
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/*
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* make_attrmap
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*
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* Utility routine to allocate an attribute map in the current memory
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* context.
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*/
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AttrMap*
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make_attrmap(intmaplen)
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{
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AttrMap*res;
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res= (AttrMap*)palloc0(sizeof(AttrMap));
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res->maplen=maplen;
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res->attnums= (AttrNumber*)palloc0(sizeof(AttrNumber)*maplen);
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returnres;
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}
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/*
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* free_attrmap
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*
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* Utility routine to release an attribute map.
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*/
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void
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free_attrmap(AttrMap*map)
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{
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pfree(map->attnums);
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pfree(map);
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}
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/*
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* build_attrmap_by_position
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*
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* Return a palloc'd bare attribute map for tuple conversion, matching input
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* and output columns by position. Dropped columns are ignored in both input
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* and output, marked as 0. This is normally a subroutine for
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* convert_tuples_by_position in tupconvert.c, but it can be used standalone.
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*
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* Note: the errdetail messages speak of indesc as the "returned" rowtype,
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* outdesc as the "expected" rowtype. This is okay for current uses but
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* might need generalization in future.
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*/
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AttrMap*
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build_attrmap_by_position(TupleDescindesc,
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TupleDescoutdesc,
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constchar*msg)
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{
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AttrMap*attrMap;
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intnincols;
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intnoutcols;
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intn;
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inti;
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intj;
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boolsame;
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/*
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* The length is computed as the number of attributes of the expected
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* rowtype as it includes dropped attributes in its count.
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*/
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n=outdesc->natts;
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attrMap=make_attrmap(n);
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j=0;/* j is next physical input attribute */
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nincols=noutcols=0;/* these count non-dropped attributes */
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same= true;
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for (i=0;i<n;i++)
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{
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Form_pg_attributeatt=TupleDescAttr(outdesc,i);
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Oidatttypid;
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int32atttypmod;
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if (att->attisdropped)
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continue;/* attrMap->attnums[i] is already 0 */
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noutcols++;
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atttypid=att->atttypid;
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atttypmod=att->atttypmod;
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for (;j<indesc->natts;j++)
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{
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att=TupleDescAttr(indesc,j);
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if (att->attisdropped)
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continue;
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nincols++;
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/* Found matching column, now check type */
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if (atttypid!=att->atttypid||
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(atttypmod!=att->atttypmod&&atttypmod >=0))
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ereport(ERROR,
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(errcode(ERRCODE_DATATYPE_MISMATCH),
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errmsg_internal("%s",_(msg)),
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errdetail("Returned type %s does not match expected type %s in column %d.",
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format_type_with_typemod(att->atttypid,
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att->atttypmod),
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format_type_with_typemod(atttypid,
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atttypmod),
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noutcols)));
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attrMap->attnums[i]= (AttrNumber) (j+1);
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j++;
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break;
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}
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if (attrMap->attnums[i]==0)
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same= false;/* we'll complain below */
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}
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/* Check for unused input columns */
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for (;j<indesc->natts;j++)
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{
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if (TupleDescAttr(indesc,j)->attisdropped)
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continue;
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nincols++;
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same= false;/* we'll complain below */
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}
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/* Report column count mismatch using the non-dropped-column counts */
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if (!same)
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ereport(ERROR,
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(errcode(ERRCODE_DATATYPE_MISMATCH),
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errmsg_internal("%s",_(msg)),
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errdetail("Number of returned columns (%d) does not match "
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"expected column count (%d).",
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nincols,noutcols)));
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/* Check if the map has a one-to-one match */
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if (check_attrmap_match(indesc,outdesc,attrMap))
156+
{
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/* Runtime conversion is not needed */
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free_attrmap(attrMap);
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returnNULL;
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}
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returnattrMap;
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}
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/*
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* build_attrmap_by_name
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*
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* Return a palloc'd bare attribute map for tuple conversion, matching input
169+
* and output columns by name. (Dropped columns are ignored in both input and
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* output.) This is normally a subroutine for convert_tuples_by_name in
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* tupconvert.c, but can be used standalone.
172+
*/
173+
AttrMap*
174+
build_attrmap_by_name(TupleDescindesc,
175+
TupleDescoutdesc)
176+
{
177+
AttrMap*attrMap;
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intoutnatts;
179+
intinnatts;
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inti;
181+
intnextindesc=-1;
182+
183+
outnatts=outdesc->natts;
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innatts=indesc->natts;
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186+
attrMap=make_attrmap(outnatts);
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for (i=0;i<outnatts;i++)
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{
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Form_pg_attributeoutatt=TupleDescAttr(outdesc,i);
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char*attname;
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Oidatttypid;
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int32atttypmod;
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intj;
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if (outatt->attisdropped)
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continue;/* attrMap->attnums[i] is already 0 */
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attname=NameStr(outatt->attname);
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atttypid=outatt->atttypid;
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atttypmod=outatt->atttypmod;
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/*
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* Now search for an attribute with the same name in the indesc. It
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* seems likely that a partitioned table will have the attributes in
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* the same order as the partition, so the search below is optimized
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* for that case. It is possible that columns are dropped in one of
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* the relations, but not the other, so we use the 'nextindesc'
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* counter to track the starting point of the search. If the inner
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* loop encounters dropped columns then it will have to skip over
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* them, but it should leave 'nextindesc' at the correct position for
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* the next outer loop.
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*/
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for (j=0;j<innatts;j++)
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{
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Form_pg_attributeinatt;
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nextindesc++;
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if (nextindesc >=innatts)
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nextindesc=0;
219+
220+
inatt=TupleDescAttr(indesc,nextindesc);
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if (inatt->attisdropped)
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continue;
223+
if (strcmp(attname,NameStr(inatt->attname))==0)
224+
{
225+
/* Found it, check type */
226+
if (atttypid!=inatt->atttypid||atttypmod!=inatt->atttypmod)
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ereport(ERROR,
228+
(errcode(ERRCODE_DATATYPE_MISMATCH),
229+
errmsg("could not convert row type"),
230+
errdetail("Attribute \"%s\" of type %s does not match corresponding attribute of type %s.",
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attname,
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format_type_be(outdesc->tdtypeid),
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format_type_be(indesc->tdtypeid))));
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attrMap->attnums[i]=inatt->attnum;
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break;
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}
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}
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if (attrMap->attnums[i]==0)
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ereport(ERROR,
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(errcode(ERRCODE_DATATYPE_MISMATCH),
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errmsg("could not convert row type"),
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errdetail("Attribute \"%s\" of type %s does not exist in type %s.",
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attname,
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format_type_be(outdesc->tdtypeid),
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format_type_be(indesc->tdtypeid))));
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}
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returnattrMap;
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}
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/*
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* build_attrmap_by_name_if_req
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*
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* Returns mapping created by build_attrmap_by_name, or NULL if no
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* conversion is required. This is a convenience routine for
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* convert_tuples_by_name() in tupconvert.c and other functions, but it
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* can be used standalone.
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*/
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AttrMap*
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build_attrmap_by_name_if_req(TupleDescindesc,
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TupleDescoutdesc)
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{
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AttrMap*attrMap;
263+
264+
/* Verify compatibility and prepare attribute-number map */
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attrMap=build_attrmap_by_name(indesc,outdesc);
266+
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/* Check if the map has a one-to-one match */
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if (check_attrmap_match(indesc,outdesc,attrMap))
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{
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/* Runtime conversion is not needed */
271+
free_attrmap(attrMap);
272+
returnNULL;
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}
274+
275+
returnattrMap;
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}
277+
278+
/*
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* check_attrmap_match
280+
*
281+
* Check to see if the map is a one-to-one match, in which case we need
282+
* not to do a tuple conversion, and the attribute map is not necessary.
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*/
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staticbool
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check_attrmap_match(TupleDescindesc,
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TupleDescoutdesc,
287+
AttrMap*attrMap)
288+
{
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inti;
290+
291+
/* no match if attribute numbers are not the same */
292+
if (indesc->natts!=outdesc->natts)
293+
return false;
294+
295+
for (i=0;i<attrMap->maplen;i++)
296+
{
297+
Form_pg_attributeinatt;
298+
Form_pg_attributeoutatt;
299+
300+
if (attrMap->attnums[i]== (i+1))
301+
continue;
302+
303+
/*
304+
* If it's a dropped column and the corresponding input column is also
305+
* dropped, we don't need a conversion. However, attlen and attalign
306+
* must agree.
307+
*/
308+
inatt=TupleDescAttr(indesc,i);
309+
outatt=TupleDescAttr(outdesc,i);
310+
if (attrMap->attnums[i]==0&&
311+
inatt->attisdropped&&
312+
inatt->attlen==outatt->attlen&&
313+
inatt->attalign==outatt->attalign)
314+
continue;
315+
316+
return false;
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}
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319+
return true;
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}

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