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Allow omitting one or both boundaries in an array slice specifier.

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Omitted boundaries represent the upper or lower limit of the corresponding
array subscript.  This allows simpler specification of many common
use-cases.

(Revised version of commit 9246af6799)

YUriy Zhuravlev
This commit is contained in:
Tom Lane
2015-12-22 21:05:16 -05:00
parent 0ba3f3bc65
commit 6efbded6e4
15 changed files with 302 additions and 33 deletions
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59
src/backend/parser/parse_node.c
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@ -311,18 +311,18 @@ transformArraySubscripts(ParseState *pstate,
elementType = transformArrayType(&arrayType, &arrayTypMod);
/*
* A list containing only single subscripts refers to a single array
* element. If any of the items are double subscripts (lower:upper), then
* the subscript expression means an array slice operation. In this case,
* we supply a default lower bound of 1 for any items that contain only a
* single subscript. We have to prescan the indirection list to see if
* there are any double subscripts.
* A list containing only simple subscripts refers to a single array
* element. If any of the items are slice specifiers (lower:upper), then
* the subscript expression means an array slice operation. In this case,
* we convert any non-slice items to slices by treating the single
* subscript as the upper bound and supplying an assumed lower bound of 1.
* We have to prescan the list to see if there are any slice items.
*/
foreach(idx, indirection)
{
A_Indices *ai = (A_Indices *) lfirst(idx);
if (ai->lidx != NULL)
if (ai->is_slice)
{
isSlice = true;
break;
@ -356,7 +356,7 @@ transformArraySubscripts(ParseState *pstate,
errmsg("array subscript must have type integer"),
parser_errposition(pstate, exprLocation(ai->lidx))));
}
else
else if (!ai->is_slice)
{
/* Make a constant 1 */
subexpr = (Node *) makeConst(INT4OID,
@ -367,21 +367,38 @@ transformArraySubscripts(ParseState *pstate,
false,
true); /* pass by value */
}
else
{
/* Slice with omitted lower bound, put NULL into the list */
subexpr = NULL;
}
lowerIndexpr = lappend(lowerIndexpr, subexpr);
}
subexpr = transformExpr(pstate, ai->uidx, pstate->p_expr_kind);
/* If it's not int4 already, try to coerce */
subexpr = coerce_to_target_type(pstate,
subexpr, exprType(subexpr),
INT4OID, -1,
COERCION_ASSIGNMENT,
COERCE_IMPLICIT_CAST,
-1);
if (subexpr == NULL)
ereport(ERROR,
(errcode(ERRCODE_DATATYPE_MISMATCH),
errmsg("array subscript must have type integer"),
parser_errposition(pstate, exprLocation(ai->uidx))));
else
Assert(ai->lidx == NULL && !ai->is_slice);
if (ai->uidx)
{
subexpr = transformExpr(pstate, ai->uidx, pstate->p_expr_kind);
/* If it's not int4 already, try to coerce */
subexpr = coerce_to_target_type(pstate,
subexpr, exprType(subexpr),
INT4OID, -1,
COERCION_ASSIGNMENT,
COERCE_IMPLICIT_CAST,
-1);
if (subexpr == NULL)
ereport(ERROR,
(errcode(ERRCODE_DATATYPE_MISMATCH),
errmsg("array subscript must have type integer"),
parser_errposition(pstate, exprLocation(ai->uidx))));
}
else
{
/* Slice with omitted upper bound, put NULL into the list */
Assert(isSlice && ai->is_slice);
subexpr = NULL;
}
upperIndexpr = lappend(upperIndexpr, subexpr);
}