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Commit9550e83

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Transform ALTER TABLE/SET TYPE/USING expr during parse analysis
This lets later stages have access to the transformed expression; inparticular it allows DDL-deparsing code during event triggers to passthe transformed expression to ruleutils.c, so that the complete commandcan be deparsed.This shuffles the timing of the transform calls a bit: previously,nothing was transformed during parse analysis, and only theRELKIND_RELATION case was being handled during execution. After thispatch, all expressions are transformed during parse analysis (includingthose for relkinds other than RELATION), and the error for otherrelation kinds is thrown only during execution. So we do more work thanbefore to reject some bogus cases. That seems acceptable.
1 parent4ff695b commit9550e83

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2 files changed

+44
-31
lines changed

2 files changed

+44
-31
lines changed

‎src/backend/commands/tablecmds.c

Lines changed: 7 additions & 28 deletions
Original file line numberDiff line numberDiff line change
@@ -7776,7 +7776,7 @@ ATPrepAlterColumnType(List **wqueue,
77767776
char*colName=cmd->name;
77777777
ColumnDef*def= (ColumnDef*)cmd->def;
77787778
TypeName*typeName=def->typeName;
7779-
Node*transform=def->raw_default;
7779+
Node*transform=def->cooked_default;
77807780
HeapTupletuple;
77817781
Form_pg_attributeattTup;
77827782
AttrNumberattnum;
@@ -7835,34 +7835,13 @@ ATPrepAlterColumnType(List **wqueue,
78357835
{
78367836
/*
78377837
* Set up an expression to transform the old data value to the new
7838-
* type. If a USING option was given,transform and use that
7839-
*expression, else just take the old value and try to coerce it. We
7840-
* do this first so that type incompatibility can be detected before
7841-
* we waste effort, and because we need the expression to be parsed
7842-
* against the original table row type.
7838+
* type. If a USING option was given,use the expression as transformed
7839+
*by transformAlterTableStmt, else just take the old value and try to
7840+
*coerce it. Wedo this first so that type incompatibility can be
7841+
*detected beforewe waste effort, and because we need the expression
7842+
*to be parsedagainst the original table row type.
78437843
*/
7844-
if (transform)
7845-
{
7846-
RangeTblEntry*rte;
7847-
7848-
/* Expression must be able to access vars of old table */
7849-
rte=addRangeTableEntryForRelation(pstate,
7850-
rel,
7851-
NULL,
7852-
false,
7853-
true);
7854-
addRTEtoQuery(pstate,rte, false, true, true);
7855-
7856-
transform=transformExpr(pstate,transform,
7857-
EXPR_KIND_ALTER_COL_TRANSFORM);
7858-
7859-
/* It can't return a set */
7860-
if (expression_returns_set(transform))
7861-
ereport(ERROR,
7862-
(errcode(ERRCODE_DATATYPE_MISMATCH),
7863-
errmsg("transform expression must not return a set")));
7864-
}
7865-
else
7844+
if (!transform)
78667845
{
78677846
transform= (Node*)makeVar(1,attnum,
78687847
attTup->atttypid,attTup->atttypmod,

‎src/backend/parser/parse_utilcmd.c

Lines changed: 37 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -2372,6 +2372,7 @@ transformAlterTableStmt(Oid relid, AlterTableStmt *stmt,
23722372
List*newcmds=NIL;
23732373
boolskipValidation= true;
23742374
AlterTableCmd*newcmd;
2375+
RangeTblEntry*rte;
23752376

23762377
/*
23772378
* We must not scribble on the passed-in AlterTableStmt, so copy it. (This
@@ -2382,10 +2383,17 @@ transformAlterTableStmt(Oid relid, AlterTableStmt *stmt,
23822383
/* Caller is responsible for locking the relation */
23832384
rel=relation_open(relid,NoLock);
23842385

2385-
/* Set up pstateand CreateStmtContext*/
2386+
/* Set up pstate */
23862387
pstate=make_parsestate(NULL);
23872388
pstate->p_sourcetext=queryString;
2389+
rte=addRangeTableEntryForRelation(pstate,
2390+
rel,
2391+
NULL,
2392+
false,
2393+
true);
2394+
addRTEtoQuery(pstate,rte, false, true, true);
23882395

2396+
/* Set up CreateStmtContext */
23892397
cxt.pstate=pstate;
23902398
if (stmt->relkind==OBJECT_FOREIGN_TABLE)
23912399
{
@@ -2413,8 +2421,8 @@ transformAlterTableStmt(Oid relid, AlterTableStmt *stmt,
24132421

24142422
/*
24152423
* The only subtypes that currently require parse transformation handling
2416-
* are ADD COLUMN andADD CONSTRAINT. These largely re-use code from
2417-
* CREATE TABLE.
2424+
* are ADD COLUMN,ADD CONSTRAINT and SET DATA TYPE. These largely re-use
2425+
*code fromCREATE TABLE.
24182426
*/
24192427
foreach(lcmd,stmt->cmds)
24202428
{
@@ -2446,6 +2454,7 @@ transformAlterTableStmt(Oid relid, AlterTableStmt *stmt,
24462454
newcmds=lappend(newcmds,cmd);
24472455
break;
24482456
}
2457+
24492458
caseAT_AddConstraint:
24502459

24512460
/*
@@ -2472,6 +2481,31 @@ transformAlterTableStmt(Oid relid, AlterTableStmt *stmt,
24722481
newcmds=lappend(newcmds,cmd);
24732482
break;
24742483

2484+
caseAT_AlterColumnType:
2485+
{
2486+
ColumnDef*def= (ColumnDef*)cmd->def;
2487+
2488+
/*
2489+
* For ALTER COLUMN TYPE, transform the USING clause if
2490+
* one was specified.
2491+
*/
2492+
if (def->raw_default)
2493+
{
2494+
def->cooked_default=
2495+
transformExpr(pstate,def->raw_default,
2496+
EXPR_KIND_ALTER_COL_TRANSFORM);
2497+
2498+
/* it can't return a set */
2499+
if (expression_returns_set(def->cooked_default))
2500+
ereport(ERROR,
2501+
(errcode(ERRCODE_DATATYPE_MISMATCH),
2502+
errmsg("transform expression must not return a set")));
2503+
}
2504+
2505+
newcmds=lappend(newcmds,cmd);
2506+
break;
2507+
}
2508+
24752509
default:
24762510
newcmds=lappend(newcmds,cmd);
24772511
break;

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