postgres/src/backend/parser/parse_node.c

/*-------------------------------------------------------------------------
 *
 * parse_node.c
 *	  various routines that make nodes for querytrees
 *
 * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *	  $PostgreSQL: pgsql/src/backend/parser/parse_node.c,v 1.101 2008/08/25 22:42:33 tgl Exp $
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "access/heapam.h"
#include "catalog/pg_type.h"
#include "mb/pg_wchar.h"
#include "nodes/makefuncs.h"
#include "nodes/nodeFuncs.h"
#include "parser/parsetree.h"
#include "parser/parse_coerce.h"
#include "parser/parse_expr.h"
#include "parser/parse_relation.h"
#include "utils/builtins.h"
#include "utils/int8.h"
#include "utils/syscache.h"
#include "utils/varbit.h"


/*
 * make_parsestate
 *		Allocate and initialize a new ParseState.
 *
 * Caller should eventually release the ParseState via free_parsestate().
 */
ParseState *
make_parsestate(ParseState *parentParseState)
{
	ParseState *pstate;

	pstate = palloc0(sizeof(ParseState));

	pstate->parentParseState = parentParseState;

	/* Fill in fields that don't start at null/false/zero */
	pstate->p_next_resno = 1;

	if (parentParseState)
	{
		pstate->p_sourcetext = parentParseState->p_sourcetext;
		pstate->p_variableparams = parentParseState->p_variableparams;
	}

	return pstate;
}

/*
 * free_parsestate
 *		Release a ParseState and any subsidiary resources.
 */
void
free_parsestate(ParseState *pstate)
{
	/*
	 * Check that we did not produce too many resnos; at the very least we
	 * cannot allow more than 2^16, since that would exceed the range of a
	 * AttrNumber. It seems safest to use MaxTupleAttributeNumber.
	 */
	if (pstate->p_next_resno - 1 > MaxTupleAttributeNumber)
		ereport(ERROR,
				(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
				 errmsg("target lists can have at most %d entries",
						MaxTupleAttributeNumber)));

	if (pstate->p_target_relation != NULL)
		heap_close(pstate->p_target_relation, NoLock);

	pfree(pstate);
}


/*
 * parser_errposition
 *		Report a parse-analysis-time cursor position, if possible.
 *
 * This is expected to be used within an ereport() call.  The return value
 * is a dummy (always 0, in fact).
 *
 * The locations stored in raw parsetrees are byte offsets into the source
 * string.	We have to convert them to 1-based character indexes for reporting
 * to clients.	(We do things this way to avoid unnecessary overhead in the
 * normal non-error case: computing character indexes would be much more
 * expensive than storing token offsets.)
 */
int
parser_errposition(ParseState *pstate, int location)
{
	int			pos;

	/* No-op if location was not provided */
	if (location < 0)
		return 0;
	/* Can't do anything if source text is not available */
	if (pstate == NULL || pstate->p_sourcetext == NULL)
		return 0;
	/* Convert offset to character number */
	pos = pg_mbstrlen_with_len(pstate->p_sourcetext, location) + 1;
	/* And pass it to the ereport mechanism */
	return errposition(pos);
}


/*
 * make_var
 *		Build a Var node for an attribute identified by RTE and attrno
 */
Var *
make_var(ParseState *pstate, RangeTblEntry *rte, int attrno)
{
	int			vnum,
				sublevels_up;
	Oid			vartypeid;
	int32		type_mod;

	vnum = RTERangeTablePosn(pstate, rte, &sublevels_up);
	get_rte_attribute_type(rte, attrno, &vartypeid, &type_mod);
	return makeVar(vnum, attrno, vartypeid, type_mod, sublevels_up);
}

/*
 * transformArrayType()
 *		Get the element type of an array type in preparation for subscripting
 */
Oid
transformArrayType(Oid arrayType)
{
	Oid			elementType;
	HeapTuple	type_tuple_array;
	Form_pg_type type_struct_array;

	/* Get the type tuple for the array */
	type_tuple_array = SearchSysCache(TYPEOID,
									  ObjectIdGetDatum(arrayType),
									  0, 0, 0);
	if (!HeapTupleIsValid(type_tuple_array))
		elog(ERROR, "cache lookup failed for type %u", arrayType);
	type_struct_array = (Form_pg_type) GETSTRUCT(type_tuple_array);

	/* needn't check typisdefined since this will fail anyway */

	elementType = type_struct_array->typelem;
	if (elementType == InvalidOid)
		ereport(ERROR,
				(errcode(ERRCODE_DATATYPE_MISMATCH),
				 errmsg("cannot subscript type %s because it is not an array",
						format_type_be(arrayType))));

	ReleaseSysCache(type_tuple_array);

	return elementType;
}

/*
 * transformArraySubscripts()
 *		Transform array subscripting.  This is used for both
 *		array fetch and array assignment.
 *
 * In an array fetch, we are given a source array value and we produce an
 * expression that represents the result of extracting a single array element
 * or an array slice.
 *
 * In an array assignment, we are given a destination array value plus a
 * source value that is to be assigned to a single element or a slice of
 * that array.	We produce an expression that represents the new array value
 * with the source data inserted into the right part of the array.
 *
 * pstate		Parse state
 * arrayBase	Already-transformed expression for the array as a whole
 * arrayType	OID of array's datatype (should match type of arrayBase)
 * elementType	OID of array's element type (fetch with transformArrayType,
 *				or pass InvalidOid to do it here)
 * elementTypMod typmod to be applied to array elements (if storing) or of
 *				the source array (if fetching)
 * indirection	Untransformed list of subscripts (must not be NIL)
 * assignFrom	NULL for array fetch, else transformed expression for source.
 */
ArrayRef *
transformArraySubscripts(ParseState *pstate,
						 Node *arrayBase,
						 Oid arrayType,
						 Oid elementType,
						 int32 elementTypMod,
						 List *indirection,
						 Node *assignFrom)
{
	bool		isSlice = false;
	List	   *upperIndexpr = NIL;
	List	   *lowerIndexpr = NIL;
	ListCell   *idx;
	ArrayRef   *aref;

	/* Caller may or may not have bothered to determine elementType */
	if (!OidIsValid(elementType))
		elementType = transformArrayType(arrayType);

	/*
	 * 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.
	 */
	foreach(idx, indirection)
	{
		A_Indices  *ai = (A_Indices *) lfirst(idx);

		if (ai->lidx != NULL)
		{
			isSlice = true;
			break;
		}
	}

	/*
	 * Transform the subscript expressions.
	 */
	foreach(idx, indirection)
	{
		A_Indices  *ai = (A_Indices *) lfirst(idx);
		Node	   *subexpr;

		Assert(IsA(ai, A_Indices));
		if (isSlice)
		{
			if (ai->lidx)
			{
				subexpr = transformExpr(pstate, ai->lidx);
				/* 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);
				if (subexpr == NULL)
					ereport(ERROR,
							(errcode(ERRCODE_DATATYPE_MISMATCH),
						  errmsg("array subscript must have type integer")));
			}
			else
			{
				/* Make a constant 1 */
				subexpr = (Node *) makeConst(INT4OID,
											 -1,
											 sizeof(int32),
											 Int32GetDatum(1),
											 false,
											 true);		/* pass by value */
			}
			lowerIndexpr = lappend(lowerIndexpr, subexpr);
		}
		subexpr = transformExpr(pstate, ai->uidx);
		/* 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);
		if (subexpr == NULL)
			ereport(ERROR,
					(errcode(ERRCODE_DATATYPE_MISMATCH),
					 errmsg("array subscript must have type integer")));
		upperIndexpr = lappend(upperIndexpr, subexpr);
	}

	/*
	 * If doing an array store, coerce the source value to the right type.
	 * (This should agree with the coercion done by transformAssignedExpr.)
	 */
	if (assignFrom != NULL)
	{
		Oid			typesource = exprType(assignFrom);
		Oid			typeneeded = isSlice ? arrayType : elementType;

		assignFrom = coerce_to_target_type(pstate,
										   assignFrom, typesource,
										   typeneeded, elementTypMod,
										   COERCION_ASSIGNMENT,
										   COERCE_IMPLICIT_CAST);
		if (assignFrom == NULL)
			ereport(ERROR,
					(errcode(ERRCODE_DATATYPE_MISMATCH),
					 errmsg("array assignment requires type %s"
							" but expression is of type %s",
							format_type_be(typeneeded),
							format_type_be(typesource)),
			   errhint("You will need to rewrite or cast the expression.")));
	}

	/*
	 * Ready to build the ArrayRef node.
	 */
	aref = makeNode(ArrayRef);
	aref->refarraytype = arrayType;
	aref->refelemtype = elementType;
	aref->reftypmod = elementTypMod;
	aref->refupperindexpr = upperIndexpr;
	aref->reflowerindexpr = lowerIndexpr;
	aref->refexpr = (Expr *) arrayBase;
	aref->refassgnexpr = (Expr *) assignFrom;

	return aref;
}

/*
 * make_const
 *
 *	Convert a Value node (as returned by the grammar) to a Const node
 *	of the "natural" type for the constant.  Note that this routine is
 *	only used when there is no explicit cast for the constant, so we
 *	have to guess what type is wanted.
 *
 *	For string literals we produce a constant of type UNKNOWN ---- whose
 *	representation is the same as cstring, but it indicates to later type
 *	resolution that we're not sure yet what type it should be considered.
 *	Explicit "NULL" constants are also typed as UNKNOWN.
 *
 *	For integers and floats we produce int4, int8, or numeric depending
 *	on the value of the number.  XXX We should produce int2 as well,
 *	but additional cleanup is needed before we can do that; there are
 *	too many examples that fail if we try.
 */
Const *
make_const(Value *value)
{
	Datum		val;
	int64		val64;
	Oid			typeid;
	int			typelen;
	bool		typebyval;
	Const	   *con;

	switch (nodeTag(value))
	{
		case T_Integer:
			val = Int32GetDatum(intVal(value));

			typeid = INT4OID;
			typelen = sizeof(int32);
			typebyval = true;
			break;

		case T_Float:
			/* could be an oversize integer as well as a float ... */
			if (scanint8(strVal(value), true, &val64))
			{
				/*
				 * It might actually fit in int32. Probably only INT_MIN can
				 * occur, but we'll code the test generally just to be sure.
				 */
				int32		val32 = (int32) val64;

				if (val64 == (int64) val32)
				{
					val = Int32GetDatum(val32);

					typeid = INT4OID;
					typelen = sizeof(int32);
					typebyval = true;
				}
				else
				{
					val = Int64GetDatum(val64);

					typeid = INT8OID;
					typelen = sizeof(int64);
					typebyval = FLOAT8PASSBYVAL;	/* int8 and float8 alike */
				}
			}
			else
			{
				val = DirectFunctionCall3(numeric_in,
										  CStringGetDatum(strVal(value)),
										  ObjectIdGetDatum(InvalidOid),
										  Int32GetDatum(-1));

				typeid = NUMERICOID;
				typelen = -1;	/* variable len */
				typebyval = false;
			}
			break;

		case T_String:

			/*
			 * We assume here that UNKNOWN's internal representation is the
			 * same as CSTRING
			 */
			val = CStringGetDatum(strVal(value));

			typeid = UNKNOWNOID;	/* will be coerced later */
			typelen = -2;		/* cstring-style varwidth type */
			typebyval = false;
			break;

		case T_BitString:
			val = DirectFunctionCall3(bit_in,
									  CStringGetDatum(strVal(value)),
									  ObjectIdGetDatum(InvalidOid),
									  Int32GetDatum(-1));
			typeid = BITOID;
			typelen = -1;
			typebyval = false;
			break;

		case T_Null:
			/* return a null const */
			con = makeConst(UNKNOWNOID,
							-1,
							-2,
							(Datum) 0,
							true,
							false);
			return con;

		default:
			elog(ERROR, "unrecognized node type: %d", (int) nodeTag(value));
			return NULL;		/* keep compiler quiet */
	}

	con = makeConst(typeid,
					-1,			/* typmod -1 is OK for all cases */
					typelen,
					val,
					false,
					typebyval);

	return con;
}