parse_node.c

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/*-------------------------------------------------------------------------
 *
 * parse_node.c
 *    various routines that make nodes for querytrees
 *
 * Portions Copyright (c) 1996-2021, 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/htup_details.h"
#include "access/table.h"
#include "catalog/pg_type.h"
#include "mb/pg_wchar.h"
#include "nodes/makefuncs.h"
#include "nodes/nodeFuncs.h"
#include "nodes/subscripting.h"
#include "parser/parse_coerce.h"
#include "parser/parse_expr.h"
#include "parser/parse_relation.h"
#include "parser/parsetree.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)
        table_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);
}


/*
 * transformContainerType()
 *      Identify the actual container type for a subscripting operation.
 *
 * containerType/containerTypmod are modified if necessary to identify
 * the actual container type and typmod.  This mainly involves smashing
 * any domain to its base type, but there are some special considerations.
 * Note that caller still needs to check if the result type is a container.
 */
void
transformContainerType(Oid *containerType, int32 *containerTypmod)
{
    /*
     * 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 container type, not the
     * domain itself. (Note that we provide no method whereby the creator of a
     * domain over a container type could hide its ability to be subscripted.)
     */
    *containerType = getBaseTypeAndTypmod(*containerType, containerTypmod);

    /*
     * 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 (*containerType == INT2VECTOROID)
        *containerType = INT2ARRAYOID;
    else if (*containerType == OIDVECTOROID)
        *containerType = OIDARRAYOID;
}

/*
 * transformContainerSubscripts()
 *      Transform container (array, etc) subscripting.  This is used for both
 *      container fetch and container assignment.
 *
 * In a container fetch, we are given a source container value and we produce
 * an expression that represents the result of extracting a single container
 * element or a container slice.
 *
 * Container assignments are treated basically the same as container fetches
 * here.  The caller will modify the result node to insert the source value
 * that is to be assigned to the element or slice that a fetch would have
 * retrieved.  The execution result will be a new container value with
 * the source value inserted into the right part of the container.
 *
 * For both cases, if the source is of a domain-over-container type, the
 * result is the same as if it had been of the container 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
 * containerBase    Already-transformed expression for the container as a whole
 * containerType    OID of container's datatype (should match type of
 *                  containerBase, or be the base type of containerBase's
 *                  domain type)
 * containerTypMod  typmod for the container
 * indirection      Untransformed list of subscripts (must not be NIL)
 * isAssignment     True if this will become a container assignment.
 */
SubscriptingRef *
transformContainerSubscripts(ParseState *pstate,
                             Node *containerBase,
                             Oid containerType,
                             int32 containerTypMod,
                             List *indirection,
                             bool isAssignment)
{
    SubscriptingRef *sbsref;
    const SubscriptRoutines *sbsroutines;
    Oid         elementType;
    bool        isSlice = false;
    ListCell   *idx;

    /*
     * Determine the actual container type, smashing any domain.  In the
     * assignment case the caller already did this, since it also needs to
     * know the actual container type.
     */
    if (!isAssignment)
        transformContainerType(&containerType, &containerTypMod);

    /*
     * Verify that the container type is subscriptable, and get its support
     * functions and typelem.
     */
    sbsroutines = getSubscriptingRoutines(containerType, &elementType);
    if (!sbsroutines)
        ereport(ERROR,
                (errcode(ERRCODE_DATATYPE_MISMATCH),
                 errmsg("cannot subscript type %s because it does not support subscripting",
                        format_type_be(containerType)),
                 parser_errposition(pstate, exprLocation(containerBase))));

    /*
     * Detect whether any of the indirection items are slice specifiers.
     *
     * A list containing only simple subscripts refers to a single container
     * element.  If any of the items are slice specifiers (lower:upper), then
     * the subscript expression means a container slice operation.
     */
    foreach(idx, indirection)
    {
        A_Indices  *ai = lfirst_node(A_Indices, idx);

        if (ai->is_slice)
        {
            isSlice = true;
            break;
        }
    }

    /*
     * Ready to build the SubscriptingRef node.
     */
    sbsref = makeNode(SubscriptingRef);

    sbsref->refcontainertype = containerType;
    sbsref->refelemtype = elementType;
    /* refrestype is to be set by container-specific logic */
    sbsref->reftypmod = containerTypMod;
    /* refcollid will be set by parse_collate.c */
    /* refupperindexpr, reflowerindexpr are to be set by container logic */
    sbsref->refexpr = (Expr *) containerBase;
    sbsref->refassgnexpr = NULL;    /* caller will fill if it's an assignment */

    /*
     * Call the container-type-specific logic to transform the subscripts and
     * determine the subscripting result type.
     */
    sbsroutines->transform(sbsref, indirection, pstate,
                           isSlice, isAssignment);

    /*
     * Verify we got a valid type (this defends, for example, against someone
     * using array_subscript_handler as typsubscript without setting typelem).
     */
    if (!OidIsValid(sbsref->refrestype))
        ereport(ERROR,
                (errcode(ERRCODE_DATATYPE_MISMATCH),
                 errmsg("cannot subscript type %s because it does not support subscripting",
                        format_type_be(containerType))));

    return sbsref;
}

/*
 * 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;
}