backend/parser/parse_node.c

/*-------------------------------------------------------------------------
 *
 * parse_node.c
 *	  various routines that make nodes for querytrees
 *
 * Portions Copyright (c) 1996-2017, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *	  src/backend/parser/parse_node.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "access/heapam.h"
#include "access/htup_details.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/lsyscache.h"
#include "utils/syscache.h"
#include "utils/varbit.h"


static void pcb_error_callback(void *arg);


/*
 * 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;
	pstate->p_resolve_unknowns = true;

	if (parentParseState)
	{
		pstate->p_sourcetext = parentParseState->p_sourcetext;
		/* all hooks are copied from parent */
		pstate->p_pre_columnref_hook = parentParseState->p_pre_columnref_hook;
		pstate->p_post_columnref_hook = parentParseState->p_post_columnref_hook;
		pstate->p_paramref_hook = parentParseState->p_paramref_hook;
		pstate->p_coerce_param_hook = parentParseState->p_coerce_param_hook;
		pstate->p_ref_hook_state = parentParseState->p_ref_hook_state;
		/* query environment stays in context for the whole parse analysis */
		pstate->p_queryEnv = parentParseState->p_queryEnv;
	}

	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);
}


/*
 * setup_parser_errposition_callback
 *		Arrange for non-parser errors to report an error position
 *
 * Sometimes the parser calls functions that aren't part of the parser
 * subsystem and can't reasonably be passed a ParseState; yet we would
 * like any errors thrown in those functions to be tagged with a parse
 * error location.  Use this function to set up an error context stack
 * entry that will accomplish that.  Usage pattern:
 *
 *		declare a local variable "ParseCallbackState pcbstate"
 *		...
 *		setup_parser_errposition_callback(&pcbstate, pstate, location);
 *		call function that might throw error;
 *		cancel_parser_errposition_callback(&pcbstate);
 */
void
setup_parser_errposition_callback(ParseCallbackState *pcbstate,
								  ParseState *pstate, int location)
{
	/* Setup error traceback support for ereport() */
	pcbstate->pstate = pstate;
	pcbstate->location = location;
	pcbstate->errcallback.callback = pcb_error_callback;
	pcbstate->errcallback.arg = (void *) pcbstate;
	pcbstate->errcallback.previous = error_context_stack;
	error_context_stack = &pcbstate->errcallback;
}

/*
 * Cancel a previously-set-up errposition callback.
 */
void
cancel_parser_errposition_callback(ParseCallbackState *pcbstate)
{
	/* Pop the error context stack */
	error_context_stack = pcbstate->errcallback.previous;
}

/*
 * Error context callback for inserting parser error location.
 *
 * Note that this will be called for *any* error occurring while the
 * callback is installed.  We avoid inserting an irrelevant error location
 * if the error is a query cancel --- are there any other important cases?
 */
static void
pcb_error_callback(void *arg)
{
	ParseCallbackState *pcbstate = (ParseCallbackState *) arg;

	if (geterrcode() != ERRCODE_QUERY_CANCELED)
		(void) parser_errposition(pcbstate->pstate, pcbstate->location);
}


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

	vnum = RTERangeTablePosn(pstate, rte, &sublevels_up);
	get_rte_attribute_type(rte, attrno, &vartypeid, &type_mod, &varcollid);
	result = makeVar(vnum, attrno, vartypeid, type_mod, varcollid, sublevels_up);
	result->location = location;
	return result;
}

/*
 * transformArrayType()
 *		Identify the types involved in a subscripting operation
 *
 * On entry, arrayType/arrayTypmod identify the type of the input value
 * to be subscripted (which could be a domain type).  These are modified
 * if necessary to identify the actual array type and typmod, and the
 * array's element type is returned.  An error is thrown if the input isn't
 * an array type.
 */
Oid
transformArrayType(Oid *arrayType, int32 *arrayTypmod)
{
	Oid			origArrayType = *arrayType;
	Oid			elementType;
	HeapTuple	type_tuple_array;
	Form_pg_type type_struct_array;

	/*
	 * If the input is a domain, smash to base type, and extract the actual
	 * typmod to be applied to the base type.  Subscripting a domain is an
	 * operation that necessarily works on the base array type, not the domain
	 * itself.  (Note that we provide no method whereby the creator of a
	 * domain over an array type could hide its ability to be subscripted.)
	 */
	*arrayType = getBaseTypeAndTypmod(*arrayType, arrayTypmod);

	/*
	 * We treat int2vector and oidvector as though they were domains over
	 * int2[] and oid[].  This is needed because array slicing could create an
	 * array that doesn't satisfy the dimensionality constraints of the
	 * xxxvector type; so we want the result of a slice operation to be
	 * considered to be of the more general type.
	 */
	if (*arrayType == INT2VECTOROID)
		*arrayType = INT2ARRAYOID;
	else if (*arrayType == OIDVECTOROID)
		*arrayType = OIDARRAYOID;

	/* Get the type tuple for the array */
	type_tuple_array = SearchSysCache1(TYPEOID, ObjectIdGetDatum(*arrayType));
	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(origArrayType))));

	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.
 *
 * For both cases, if the source array is of a domain-over-array type,
 * the result is of the base array type or its element type; essentially,
 * we must fold a domain to its base type before applying subscripting.
 * (Note that int2vector and oidvector are treated as domains here.)
 *
 * pstate		Parse state
 * arrayBase	Already-transformed expression for the array as a whole
 * arrayType	OID of array's datatype (should match type of arrayBase,
 *				or be the base type of arrayBase's domain type)
 * elementType	OID of array's element type (fetch with transformArrayType,
 *				or pass InvalidOid to do it here)
 * arrayTypMod	typmod for the array (which is also typmod for the elements)
 * 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 arrayTypMod,
						 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.  Note
	 * that if the caller did do so, arrayType/arrayTypMod must be as modified
	 * by transformArrayType, ie, smash domain to base type.
	 */
	if (!OidIsValid(elementType))
		elementType = transformArrayType(&arrayType, &arrayTypMod);

	/*
	 * 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->is_slice)
		{
			isSlice = true;
			break;
		}
	}

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

		if (isSlice)
		{
			if (ai->lidx)
			{
				subexpr = transformExpr(pstate, ai->lidx, 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->lidx))));
			}
			else if (!ai->is_slice)
			{
				/* Make a constant 1 */
				subexpr = (Node *) makeConst(INT4OID,
											 -1,
											 InvalidOid,
											 sizeof(int32),
											 Int32GetDatum(1),
											 false,
											 true); /* pass by value */
			}
			else
			{
				/* Slice with omitted lower bound, put NULL into the list */
				subexpr = NULL;
			}
			lowerIndexpr = lappend(lowerIndexpr, subexpr);
		}
		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);
	}

	/*
	 * 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;
		Node	   *newFrom;

		newFrom = coerce_to_target_type(pstate,
										assignFrom, typesource,
										typeneeded, arrayTypMod,
										COERCION_ASSIGNMENT,
										COERCE_IMPLICIT_CAST,
										-1);
		if (newFrom == 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."),
					 parser_errposition(pstate, exprLocation(assignFrom))));
		assignFrom = newFrom;
	}

	/*
	 * Ready to build the ArrayRef node.
	 */
	aref = makeNode(ArrayRef);
	aref->refarraytype = arrayType;
	aref->refelemtype = elementType;
	aref->reftypmod = arrayTypMod;
	/* refcollid will be set by parse_collate.c */
	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(ParseState *pstate, Value *value, int location)
{
	Const	   *con;
	Datum		val;
	int64		val64;
	Oid			typeid;
	int			typelen;
	bool		typebyval;
	ParseCallbackState pcbstate;

	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
			{
				/* arrange to report location if numeric_in() fails */
				setup_parser_errposition_callback(&pcbstate, pstate, location);
				val = DirectFunctionCall3(numeric_in,
										  CStringGetDatum(strVal(value)),
										  ObjectIdGetDatum(InvalidOid),
										  Int32GetDatum(-1));
				cancel_parser_errposition_callback(&pcbstate);

				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:
			/* arrange to report location if bit_in() fails */
			setup_parser_errposition_callback(&pcbstate, pstate, location);
			val = DirectFunctionCall3(bit_in,
									  CStringGetDatum(strVal(value)),
									  ObjectIdGetDatum(InvalidOid),
									  Int32GetDatum(-1));
			cancel_parser_errposition_callback(&pcbstate);
			typeid = BITOID;
			typelen = -1;
			typebyval = false;
			break;

		case T_Null:
			/* return a null const */
			con = makeConst(UNKNOWNOID,
							-1,
							InvalidOid,
							-2,
							(Datum) 0,
							true,
							false);
			con->location = location;
			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 */
					InvalidOid, /* all cases are uncollatable types */
					typelen,
					val,
					false,
					typebyval);
	con->location = location;

	return con;
}