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In ALTER COLUMN TYPE, strip any implicit coercion operations appearing
at the top level of the column's old default expression before adding an implicit coercion to the new column type. This seems to satisfy the principle of least surprise, as per discussion of bug #1290.
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@ -8,7 +8,7 @@
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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/commands/tablecmds.c,v 1.136 2004/10/21 21:33:59 tgl Exp $
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* $PostgreSQL: pgsql/src/backend/commands/tablecmds.c,v 1.137 2004/10/22 17:20:04 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -4738,13 +4738,20 @@ ATExecAlterColumnType(AlteredTableInfo *tab, Relation rel,
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* changing the column type, because build_column_default itself will
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* try to coerce, and will not issue the error message we want if it
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* fails.)
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*
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* We remove any implicit coercion steps at the top level of the old
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* default expression; this has been agreed to satisfy the principle
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* of least surprise. (The conversion to the new column type should
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* act like it started from what the user sees as the stored expression,
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* and the implicit coercions aren't going to be shown.)
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*/
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if (attTup->atthasdef)
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{
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defaultexpr = build_column_default(rel, attnum);
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Assert(defaultexpr);
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defaultexpr = strip_implicit_coercions(defaultexpr);
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defaultexpr = coerce_to_target_type(NULL, /* no UNKNOWN params */
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defaultexpr, exprType(defaultexpr),
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defaultexpr, exprType(defaultexpr),
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targettype, typename->typmod,
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COERCION_ASSIGNMENT,
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COERCE_IMPLICIT_CAST);
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@ -8,7 +8,7 @@
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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/optimizer/util/clauses.c,v 1.182 2004/10/07 18:38:49 tgl Exp $
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* $PostgreSQL: pgsql/src/backend/optimizer/util/clauses.c,v 1.183 2004/10/22 17:20:05 tgl Exp $
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*
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* HISTORY
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* AUTHOR DATE MAJOR EVENT
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@ -1021,6 +1021,41 @@ CommuteClause(OpExpr *clause)
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lsecond(clause->args) = temp;
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}
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/*
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* strip_implicit_coercions: remove implicit coercions at top level of tree
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*
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* Note: there isn't any useful thing we can do with a RowExpr here, so
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* just return it unchanged, even if it's marked as an implicit coercion.
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*/
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Node *
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strip_implicit_coercions(Node *node)
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{
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if (node == NULL)
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return NULL;
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if (IsA(node, FuncExpr))
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{
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FuncExpr *f = (FuncExpr *) node;
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if (f->funcformat == COERCE_IMPLICIT_CAST)
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return strip_implicit_coercions(linitial(f->args));
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}
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else if (IsA(node, RelabelType))
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{
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RelabelType *r = (RelabelType *) node;
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if (r->relabelformat == COERCE_IMPLICIT_CAST)
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return strip_implicit_coercions((Node *) r->arg);
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}
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else if (IsA(node, CoerceToDomain))
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{
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CoerceToDomain *c = (CoerceToDomain *) node;
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if (c->coercionformat == COERCE_IMPLICIT_CAST)
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return strip_implicit_coercions((Node *) c->arg);
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}
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return node;
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}
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/*
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* set_coercionform_dontcare: set all CoercionForm fields to COERCE_DONTCARE
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*
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