plpy_spi.c

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/*
 * interface to SPI functions
 *
 * src/pl/plpython/plpy_spi.c
 */

#include "postgres.h"

#include <limits.h>

#include "access/htup_details.h"
#include "access/xact.h"
#include "catalog/pg_type.h"
#include "executor/spi.h"
#include "mb/pg_wchar.h"
#include "parser/parse_type.h"
#include "plpy_elog.h"
#include "plpy_main.h"
#include "plpy_planobject.h"
#include "plpy_plpymodule.h"
#include "plpy_procedure.h"
#include "plpy_resultobject.h"
#include "plpy_spi.h"
#include "plpython.h"
#include "utils/memutils.h"
#include "utils/syscache.h"

static PyObject *PLy_spi_execute_query(char *query, long limit);
static PyObject *PLy_spi_execute_fetch_result(SPITupleTable *tuptable,
                                              uint64 rows, int status);
static void PLy_spi_exception_set(PyObject *excclass, ErrorData *edata);


/* prepare(query="select * from foo")
 * prepare(query="select * from foo where bar = $1", params=["text"])
 * prepare(query="select * from foo where bar = $1", params=["text"], limit=5)
 */
PyObject *
PLy_spi_prepare(PyObject *self, PyObject *args)
{
    PLyPlanObject *plan;
    PyObject   *list = NULL;
    PyObject   *volatile optr = NULL;
    char       *query;
    PLyExecutionContext *exec_ctx = PLy_current_execution_context();
    volatile MemoryContext oldcontext;
    volatile ResourceOwner oldowner;
    volatile int nargs;

    if (!PyArg_ParseTuple(args, "s|O:prepare", &query, &list))
        return NULL;

    if (list && (!PySequence_Check(list)))
    {
        PLy_exception_set(PyExc_TypeError,
                          "second argument of plpy.prepare must be a sequence");
        return NULL;
    }

    if ((plan = (PLyPlanObject *) PLy_plan_new()) == NULL)
        return NULL;

    plan->mcxt = AllocSetContextCreate(TopMemoryContext,
                                       "PL/Python plan context",
                                       ALLOCSET_DEFAULT_SIZES);
    oldcontext = MemoryContextSwitchTo(plan->mcxt);

    nargs = list ? PySequence_Length(list) : 0;

    plan->nargs = nargs;
    plan->types = nargs ? palloc0(sizeof(Oid) * nargs) : NULL;
    plan->values = nargs ? palloc0(sizeof(Datum) * nargs) : NULL;
    plan->args = nargs ? palloc0(sizeof(PLyObToDatum) * nargs) : NULL;

    MemoryContextSwitchTo(oldcontext);

    oldcontext = CurrentMemoryContext;
    oldowner = CurrentResourceOwner;

    PLy_spi_subtransaction_begin(oldcontext, oldowner);

    PG_TRY();
    {
        int         i;

        for (i = 0; i < nargs; i++)
        {
            char       *sptr;
            Oid         typeId;
            int32       typmod;

            optr = PySequence_GetItem(list, i);
            if (PyString_Check(optr))
                sptr = PyString_AsString(optr);
            else if (PyUnicode_Check(optr))
                sptr = PLyUnicode_AsString(optr);
            else
            {
                ereport(ERROR,
                        (errmsg("plpy.prepare: type name at ordinal position %d is not a string", i)));
                sptr = NULL;    /* keep compiler quiet */
            }

            /********************************************************
             * Resolve argument type names and then look them up by
             * oid in the system cache, and remember the required
             *information for input conversion.
             ********************************************************/

            parseTypeString(sptr, &typeId, &typmod, false);

            Py_DECREF(optr);

            /*
             * set optr to NULL, so we won't try to unref it again in case of
             * an error
             */
            optr = NULL;

            plan->types[i] = typeId;
            PLy_output_setup_func(&plan->args[i], plan->mcxt,
                                  typeId, typmod,
                                  exec_ctx->curr_proc);
        }

        pg_verifymbstr(query, strlen(query), false);
        plan->plan = SPI_prepare(query, plan->nargs, plan->types);
        if (plan->plan == NULL)
            elog(ERROR, "SPI_prepare failed: %s",
                 SPI_result_code_string(SPI_result));

        /* transfer plan from procCxt to topCxt */
        if (SPI_keepplan(plan->plan))
            elog(ERROR, "SPI_keepplan failed");

        PLy_spi_subtransaction_commit(oldcontext, oldowner);
    }
    PG_CATCH();
    {
        Py_DECREF(plan);
        Py_XDECREF(optr);

        PLy_spi_subtransaction_abort(oldcontext, oldowner);
        return NULL;
    }
    PG_END_TRY();

    Assert(plan->plan != NULL);
    return (PyObject *) plan;
}

/* execute(query="select * from foo", limit=5)
 * execute(plan=plan, values=(foo, bar), limit=5)
 */
PyObject *
PLy_spi_execute(PyObject *self, PyObject *args)
{
    char       *query;
    PyObject   *plan;
    PyObject   *list = NULL;
    long        limit = 0;

    if (PyArg_ParseTuple(args, "s|l", &query, &limit))
        return PLy_spi_execute_query(query, limit);

    PyErr_Clear();

    if (PyArg_ParseTuple(args, "O|Ol", &plan, &list, &limit) &&
        is_PLyPlanObject(plan))
        return PLy_spi_execute_plan(plan, list, limit);

    PLy_exception_set(PLy_exc_error, "plpy.execute expected a query or a plan");
    return NULL;
}

PyObject *
PLy_spi_execute_plan(PyObject *ob, PyObject *list, long limit)
{
    volatile int nargs;
    int         i,
                rv;
    PLyPlanObject *plan;
    volatile MemoryContext oldcontext;
    volatile ResourceOwner oldowner;
    PyObject   *ret;

    if (list != NULL)
    {
        if (!PySequence_Check(list) || PyString_Check(list) || PyUnicode_Check(list))
        {
            PLy_exception_set(PyExc_TypeError, "plpy.execute takes a sequence as its second argument");
            return NULL;
        }
        nargs = PySequence_Length(list);
    }
    else
        nargs = 0;

    plan = (PLyPlanObject *) ob;

    if (nargs != plan->nargs)
    {
        char       *sv;
        PyObject   *so = PyObject_Str(list);

        if (!so)
            PLy_elog(ERROR, "could not execute plan");
        sv = PyString_AsString(so);
        PLy_exception_set_plural(PyExc_TypeError,
                                 "Expected sequence of %d argument, got %d: %s",
                                 "Expected sequence of %d arguments, got %d: %s",
                                 plan->nargs,
                                 plan->nargs, nargs, sv);
        Py_DECREF(so);

        return NULL;
    }

    oldcontext = CurrentMemoryContext;
    oldowner = CurrentResourceOwner;

    PLy_spi_subtransaction_begin(oldcontext, oldowner);

    PG_TRY();
    {
        PLyExecutionContext *exec_ctx = PLy_current_execution_context();
        char       *volatile nulls;
        volatile int j;

        if (nargs > 0)
            nulls = palloc(nargs * sizeof(char));
        else
            nulls = NULL;

        for (j = 0; j < nargs; j++)
        {
            PLyObToDatum *arg = &plan->args[j];
            PyObject   *elem;

            elem = PySequence_GetItem(list, j);
            PG_TRY();
            {
                bool        isnull;

                plan->values[j] = PLy_output_convert(arg, elem, &isnull);
                nulls[j] = isnull ? 'n' : ' ';
            }
            PG_FINALLY();
            {
                Py_DECREF(elem);
            }
            PG_END_TRY();
        }

        rv = SPI_execute_plan(plan->plan, plan->values, nulls,
                              exec_ctx->curr_proc->fn_readonly, limit);
        ret = PLy_spi_execute_fetch_result(SPI_tuptable, SPI_processed, rv);

        if (nargs > 0)
            pfree(nulls);

        PLy_spi_subtransaction_commit(oldcontext, oldowner);
    }
    PG_CATCH();
    {
        int         k;

        /*
         * cleanup plan->values array
         */
        for (k = 0; k < nargs; k++)
        {
            if (!plan->args[k].typbyval &&
                (plan->values[k] != PointerGetDatum(NULL)))
            {
                pfree(DatumGetPointer(plan->values[k]));
                plan->values[k] = PointerGetDatum(NULL);
            }
        }

        PLy_spi_subtransaction_abort(oldcontext, oldowner);
        return NULL;
    }
    PG_END_TRY();

    for (i = 0; i < nargs; i++)
    {
        if (!plan->args[i].typbyval &&
            (plan->values[i] != PointerGetDatum(NULL)))
        {
            pfree(DatumGetPointer(plan->values[i]));
            plan->values[i] = PointerGetDatum(NULL);
        }
    }

    if (rv < 0)
    {
        PLy_exception_set(PLy_exc_spi_error,
                          "SPI_execute_plan failed: %s",
                          SPI_result_code_string(rv));
        return NULL;
    }

    return ret;
}

static PyObject *
PLy_spi_execute_query(char *query, long limit)
{
    int         rv;
    volatile MemoryContext oldcontext;
    volatile ResourceOwner oldowner;
    PyObject   *ret = NULL;

    oldcontext = CurrentMemoryContext;
    oldowner = CurrentResourceOwner;

    PLy_spi_subtransaction_begin(oldcontext, oldowner);

    PG_TRY();
    {
        PLyExecutionContext *exec_ctx = PLy_current_execution_context();

        pg_verifymbstr(query, strlen(query), false);
        rv = SPI_execute(query, exec_ctx->curr_proc->fn_readonly, limit);
        ret = PLy_spi_execute_fetch_result(SPI_tuptable, SPI_processed, rv);

        PLy_spi_subtransaction_commit(oldcontext, oldowner);
    }
    PG_CATCH();
    {
        PLy_spi_subtransaction_abort(oldcontext, oldowner);
        return NULL;
    }
    PG_END_TRY();

    if (rv < 0)
    {
        Py_XDECREF(ret);
        PLy_exception_set(PLy_exc_spi_error,
                          "SPI_execute failed: %s",
                          SPI_result_code_string(rv));
        return NULL;
    }

    return ret;
}

static PyObject *
PLy_spi_execute_fetch_result(SPITupleTable *tuptable, uint64 rows, int status)
{
    PLyResultObject *result;
    PLyExecutionContext *exec_ctx = PLy_current_execution_context();
    volatile MemoryContext oldcontext;

    result = (PLyResultObject *) PLy_result_new();
    if (!result)
    {
        SPI_freetuptable(tuptable);
        return NULL;
    }
    Py_DECREF(result->status);
    result->status = PyInt_FromLong(status);

    if (status > 0 && tuptable == NULL)
    {
        Py_DECREF(result->nrows);
        result->nrows = PyLong_FromUnsignedLongLong(rows);
    }
    else if (status > 0 && tuptable != NULL)
    {
        PLyDatumToOb ininfo;
        MemoryContext cxt;

        Py_DECREF(result->nrows);
        result->nrows = PyLong_FromUnsignedLongLong(rows);

        cxt = AllocSetContextCreate(CurrentMemoryContext,
                                    "PL/Python temp context",
                                    ALLOCSET_DEFAULT_SIZES);

        /* Initialize for converting result tuples to Python */
        PLy_input_setup_func(&ininfo, cxt, RECORDOID, -1,
                             exec_ctx->curr_proc);

        oldcontext = CurrentMemoryContext;
        PG_TRY();
        {
            MemoryContext oldcontext2;

            if (rows)
            {
                uint64      i;

                /*
                 * PyList_New() and PyList_SetItem() use Py_ssize_t for list
                 * size and list indices; so we cannot support a result larger
                 * than PY_SSIZE_T_MAX.
                 */
                if (rows > (uint64) PY_SSIZE_T_MAX)
                    ereport(ERROR,
                            (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
                             errmsg("query result has too many rows to fit in a Python list")));

                Py_DECREF(result->rows);
                result->rows = PyList_New(rows);
                if (result->rows)
                {
                    PLy_input_setup_tuple(&ininfo, tuptable->tupdesc,
                                          exec_ctx->curr_proc);

                    for (i = 0; i < rows; i++)
                    {
                        PyObject   *row = PLy_input_from_tuple(&ininfo,
                                                               tuptable->vals[i],
                                                               tuptable->tupdesc,
                                                               true);

                        PyList_SetItem(result->rows, i, row);
                    }
                }
            }

            /*
             * Save tuple descriptor for later use by result set metadata
             * functions.  Save it in TopMemoryContext so that it survives
             * outside of an SPI context.  We trust that PLy_result_dealloc()
             * will clean it up when the time is right.  (Do this as late as
             * possible, to minimize the number of ways the tupdesc could get
             * leaked due to errors.)
             */
            oldcontext2 = MemoryContextSwitchTo(TopMemoryContext);
            result->tupdesc = CreateTupleDescCopy(tuptable->tupdesc);
            MemoryContextSwitchTo(oldcontext2);
        }
        PG_CATCH();
        {
            MemoryContextSwitchTo(oldcontext);
            MemoryContextDelete(cxt);
            Py_DECREF(result);
            PG_RE_THROW();
        }
        PG_END_TRY();

        MemoryContextDelete(cxt);
        SPI_freetuptable(tuptable);

        /* in case PyList_New() failed above */
        if (!result->rows)
        {
            Py_DECREF(result);
            result = NULL;
        }
    }

    return (PyObject *) result;
}

/*
 * Utilities for running SPI functions in subtransactions.
 *
 * Usage:
 *
 *  MemoryContext oldcontext = CurrentMemoryContext;
 *  ResourceOwner oldowner = CurrentResourceOwner;
 *
 *  PLy_spi_subtransaction_begin(oldcontext, oldowner);
 *  PG_TRY();
 *  {
 *      <call SPI functions>
 *      PLy_spi_subtransaction_commit(oldcontext, oldowner);
 *  }
 *  PG_CATCH();
 *  {
 *      <do cleanup>
 *      PLy_spi_subtransaction_abort(oldcontext, oldowner);
 *      return NULL;
 *  }
 *  PG_END_TRY();
 *
 * These utilities take care of restoring connection to the SPI manager and
 * setting a Python exception in case of an abort.
 */
void
PLy_spi_subtransaction_begin(MemoryContext oldcontext, ResourceOwner oldowner)
{
    BeginInternalSubTransaction(NULL);
    /* Want to run inside function's memory context */
    MemoryContextSwitchTo(oldcontext);
}

void
PLy_spi_subtransaction_commit(MemoryContext oldcontext, ResourceOwner oldowner)
{
    /* Commit the inner transaction, return to outer xact context */
    ReleaseCurrentSubTransaction();
    MemoryContextSwitchTo(oldcontext);
    CurrentResourceOwner = oldowner;
}

void
PLy_spi_subtransaction_abort(MemoryContext oldcontext, ResourceOwner oldowner)
{
    ErrorData  *edata;
    PLyExceptionEntry *entry;
    PyObject   *exc;

    /* Save error info */
    MemoryContextSwitchTo(oldcontext);
    edata = CopyErrorData();
    FlushErrorState();

    /* Abort the inner transaction */
    RollbackAndReleaseCurrentSubTransaction();
    MemoryContextSwitchTo(oldcontext);
    CurrentResourceOwner = oldowner;

    /* Look up the correct exception */
    entry = hash_search(PLy_spi_exceptions, &(edata->sqlerrcode),
                        HASH_FIND, NULL);

    /*
     * This could be a custom error code, if that's the case fallback to
     * SPIError
     */
    exc = entry ? entry->exc : PLy_exc_spi_error;
    /* Make Python raise the exception */
    PLy_spi_exception_set(exc, edata);
    FreeErrorData(edata);
}

/*
 * Raise a SPIError, passing in it more error details, like the
 * internal query and error position.
 */
static void
PLy_spi_exception_set(PyObject *excclass, ErrorData *edata)
{
    PyObject   *args = NULL;
    PyObject   *spierror = NULL;
    PyObject   *spidata = NULL;

    args = Py_BuildValue("(s)", edata->message);
    if (!args)
        goto failure;

    /* create a new SPI exception with the error message as the parameter */
    spierror = PyObject_CallObject(excclass, args);
    if (!spierror)
        goto failure;

    spidata = Py_BuildValue("(izzzizzzzz)", edata->sqlerrcode, edata->detail, edata->hint,
                            edata->internalquery, edata->internalpos,
                            edata->schema_name, edata->table_name, edata->column_name,
                            edata->datatype_name, edata->constraint_name);
    if (!spidata)
        goto failure;

    if (PyObject_SetAttrString(spierror, "spidata", spidata) == -1)
        goto failure;

    PyErr_SetObject(excclass, spierror);

    Py_DECREF(args);
    Py_DECREF(spierror);
    Py_DECREF(spidata);
    return;

failure:
    Py_XDECREF(args);
    Py_XDECREF(spierror);
    Py_XDECREF(spidata);
    elog(ERROR, "could not convert SPI error to Python exception");
}