38bb77a5d1
code review by Tom Lane. Remaining issues: functions that take or return tuple types are likely to break if one drops (or adds!) a column in the table defining the type. Need to think about what to do here. Along the way: some code review for recent COPY changes; mark system columns attnotnull = true where appropriate, per discussion a month ago.
251 lines
7.3 KiB
C
251 lines
7.3 KiB
C
/*-------------------------------------------------------------------------
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*
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* preptlist.c
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* Routines to preprocess the parse tree target list
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*
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* This module takes care of altering the query targetlist as needed for
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* INSERT, UPDATE, and DELETE queries. For INSERT and UPDATE queries,
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* the targetlist must contain an entry for each attribute of the target
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* relation in the correct order. For both UPDATE and DELETE queries,
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* we need a junk targetlist entry holding the CTID attribute --- the
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* executor relies on this to find the tuple to be replaced/deleted.
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*
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*
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* Portions Copyright (c) 1996-2002, 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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* IDENTIFICATION
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* $Header: /cvsroot/pgsql/src/backend/optimizer/prep/preptlist.c,v 1.54 2002/08/02 18:15:06 tgl Exp $
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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/heapam.h"
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#include "catalog/pg_type.h"
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#include "nodes/makefuncs.h"
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#include "optimizer/prep.h"
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#include "parser/parsetree.h"
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static List *expand_targetlist(List *tlist, int command_type,
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Index result_relation, List *range_table);
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/*
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* preprocess_targetlist
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* Driver for preprocessing the parse tree targetlist.
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*
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* Returns the new targetlist.
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*/
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List *
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preprocess_targetlist(List *tlist,
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int command_type,
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Index result_relation,
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List *range_table)
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{
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/*
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* Sanity check: if there is a result relation, it'd better be a real
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* relation not a subquery. Else parser or rewriter messed up.
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*/
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if (result_relation)
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{
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RangeTblEntry *rte = rt_fetch(result_relation, range_table);
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if (rte->subquery != NULL || rte->relid == InvalidOid)
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elog(ERROR, "preprocess_targetlist: subquery cannot be result relation");
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}
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/*
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* for heap_formtuple to work, the targetlist must match the exact
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* order of the attributes. We also need to fill in any missing
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* attributes. -ay 10/94
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*/
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if (command_type == CMD_INSERT || command_type == CMD_UPDATE)
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tlist = expand_targetlist(tlist, command_type,
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result_relation, range_table);
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/*
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* for "update" and "delete" queries, add ctid of the result relation
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* into the target list so that the ctid will propagate through
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* execution and ExecutePlan() will be able to identify the right
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* tuple to replace or delete. This extra field is marked "junk" so
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* that it is not stored back into the tuple.
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*/
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if (command_type == CMD_UPDATE || command_type == CMD_DELETE)
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{
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Resdom *resdom;
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Var *var;
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resdom = makeResdom(length(tlist) + 1,
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TIDOID,
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-1,
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pstrdup("ctid"),
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true);
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var = makeVar(result_relation, SelfItemPointerAttributeNumber,
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TIDOID, -1, 0);
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/*
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* For an UPDATE, expand_targetlist already created a fresh tlist.
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* For DELETE, better do a listCopy so that we don't destructively
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* modify the original tlist (is this really necessary?).
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*/
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if (command_type == CMD_DELETE)
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tlist = listCopy(tlist);
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tlist = lappend(tlist, makeTargetEntry(resdom, (Node *) var));
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}
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return tlist;
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}
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/*****************************************************************************
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*
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* TARGETLIST EXPANSION
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*
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*****************************************************************************/
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/*
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* expand_targetlist
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* Given a target list as generated by the parser and a result relation,
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* add targetlist entries for any missing attributes, and ensure the
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* non-junk attributes appear in proper field order.
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*
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* NOTE: if you are tempted to put more processing here, consider whether
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* it shouldn't go in the rewriter's rewriteTargetList() instead.
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*/
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static List *
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expand_targetlist(List *tlist, int command_type,
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Index result_relation, List *range_table)
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{
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List *new_tlist = NIL;
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Relation rel;
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int attrno,
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numattrs;
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/*
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* The rewriter should have already ensured that the TLEs are in
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* correct order; but we have to insert TLEs for any missing attributes.
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*
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* Scan the tuple description in the relation's relcache entry to make
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* sure we have all the user attributes in the right order.
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*/
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rel = heap_open(getrelid(result_relation, range_table), AccessShareLock);
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numattrs = RelationGetNumberOfAttributes(rel);
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for (attrno = 1; attrno <= numattrs; attrno++)
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{
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Form_pg_attribute att_tup = rel->rd_att->attrs[attrno - 1];
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TargetEntry *new_tle = NULL;
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if (tlist != NIL)
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{
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TargetEntry *old_tle = (TargetEntry *) lfirst(tlist);
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Resdom *resdom = old_tle->resdom;
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if (!resdom->resjunk && resdom->resno == attrno)
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{
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Assert(strcmp(resdom->resname,
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NameStr(att_tup->attname)) == 0);
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new_tle = old_tle;
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tlist = lnext(tlist);
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}
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}
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if (new_tle == NULL)
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{
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/*
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* Didn't find a matching tlist entry, so make one.
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*
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* For INSERT, generate a NULL constant. (We assume the
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* rewriter would have inserted any available default value.)
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*
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* For UPDATE, generate a Var reference to the existing value of
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* the attribute, so that it gets copied to the new tuple.
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* But generate a NULL for dropped columns (we want to drop any
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* old values).
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*/
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Oid atttype = att_tup->atttypid;
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int32 atttypmod = att_tup->atttypmod;
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Node *new_expr;
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switch (command_type)
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{
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case CMD_INSERT:
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new_expr = (Node *) makeConst(atttype,
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att_tup->attlen,
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(Datum) 0,
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true, /* isnull */
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att_tup->attbyval,
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false, /* not a set */
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false);
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break;
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case CMD_UPDATE:
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/* Insert NULLs for dropped columns */
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if (att_tup->attisdropped)
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new_expr = (Node *) makeConst(atttype,
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att_tup->attlen,
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(Datum) 0,
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true, /* isnull */
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att_tup->attbyval,
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false, /* not a set */
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false);
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else
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new_expr = (Node *) makeVar(result_relation,
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attrno,
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atttype,
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atttypmod,
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0);
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break;
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default:
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elog(ERROR, "expand_targetlist: unexpected command_type");
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new_expr = NULL; /* keep compiler quiet */
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break;
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}
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new_tle = makeTargetEntry(makeResdom(attrno,
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atttype,
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atttypmod,
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pstrdup(NameStr(att_tup->attname)),
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false),
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new_expr);
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}
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new_tlist = lappend(new_tlist, new_tle);
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}
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/*
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* The remaining tlist entries should be resjunk; append them all to
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* the end of the new tlist, making sure they have resnos higher than
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* the last real attribute. (Note: although the rewriter already did
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* such renumbering, we have to do it again here in case we are doing
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* an UPDATE in a table with dropped columns, or an inheritance child
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* table with extra columns.)
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*/
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while (tlist)
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{
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TargetEntry *old_tle = (TargetEntry *) lfirst(tlist);
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Resdom *resdom = old_tle->resdom;
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if (!resdom->resjunk)
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elog(ERROR, "expand_targetlist: targetlist is not sorted correctly");
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/* Get the resno right, but don't copy unnecessarily */
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if (resdom->resno != attrno)
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{
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resdom = (Resdom *) copyObject((Node *) resdom);
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resdom->resno = attrno;
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old_tle = makeTargetEntry(resdom, old_tle->expr);
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}
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new_tlist = lappend(new_tlist, old_tle);
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attrno++;
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tlist = lnext(tlist);
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}
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heap_close(rel, AccessShareLock);
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return new_tlist;
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}
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