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tablefunc.c

/*
 * $PostgreSQL: pgsql/contrib/tablefunc/tablefunc.c,v 1.60.2.1 2009/12/29 17:41:09 heikki Exp $
 *
 *
 * tablefunc
 *
 * Sample to demonstrate C functions which return setof scalar
 * and setof composite.
 * Joe Conway <mail@joeconway.com>
 * And contributors:
 * Nabil Sayegh <postgresql@e-trolley.de>
 *
 * Copyright (c) 2002-2009, PostgreSQL Global Development Group
 *
 * Permission to use, copy, modify, and distribute this software and its
 * documentation for any purpose, without fee, and without a written agreement
 * is hereby granted, provided that the above copyright notice and this
 * paragraph and the following two paragraphs appear in all copies.
 *
 * IN NO EVENT SHALL THE AUTHORS OR DISTRIBUTORS BE LIABLE TO ANY PARTY FOR
 * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, INCLUDING
 * LOST PROFITS, ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS
 * DOCUMENTATION, EVEN IF THE AUTHOR OR DISTRIBUTORS HAVE BEEN ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 * THE AUTHORS AND DISTRIBUTORS SPECIFICALLY DISCLAIM ANY WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
 * ON AN "AS IS" BASIS, AND THE AUTHOR AND DISTRIBUTORS HAS NO OBLIGATIONS TO
 * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
 *
 */
#include "postgres.h"

#include <math.h>

#include "catalog/pg_type.h"
#include "fmgr.h"
#include "funcapi.h"
#include "executor/spi.h"
#include "lib/stringinfo.h"
#include "miscadmin.h"
#include "utils/builtins.h"
#include "utils/guc.h"
#include "utils/lsyscache.h"

#include "tablefunc.h"

PG_MODULE_MAGIC;

static HTAB *load_categories_hash(char *cats_sql, MemoryContext per_query_ctx);
static Tuplestorestate *get_crosstab_tuplestore(char *sql,
                                    HTAB *crosstab_hash,
                                    TupleDesc tupdesc,
                                    MemoryContext per_query_ctx,
                                    bool randomAccess);
static void validateConnectbyTupleDesc(TupleDesc tupdesc, bool show_branch, bool show_serial);
static bool compatCrosstabTupleDescs(TupleDesc tupdesc1, TupleDesc tupdesc2);
static bool compatConnectbyTupleDescs(TupleDesc tupdesc1, TupleDesc tupdesc2);
static void get_normal_pair(float8 *x1, float8 *x2);
static Tuplestorestate *connectby(char *relname,
              char *key_fld,
              char *parent_key_fld,
              char *orderby_fld,
              char *branch_delim,
              char *start_with,
              int max_depth,
              bool show_branch,
              bool show_serial,
              MemoryContext per_query_ctx,
              bool randomAccess,
              AttInMetadata *attinmeta);
static Tuplestorestate *build_tuplestore_recursively(char *key_fld,
                                           char *parent_key_fld,
                                           char *relname,
                                           char *orderby_fld,
                                           char *branch_delim,
                                           char *start_with,
                                           char *branch,
                                           int level,
                                           int *serial,
                                           int max_depth,
                                           bool show_branch,
                                           bool show_serial,
                                           MemoryContext per_query_ctx,
                                           AttInMetadata *attinmeta,
                                           Tuplestorestate *tupstore);
static char *quote_literal_cstr(char *rawstr);

typedef struct
{
      float8            mean;             /* mean of the distribution */
      float8            stddev;                 /* stddev of the distribution */
      float8            carry_val;        /* hold second generated value */
      bool        use_carry;        /* use second generated value */
} normal_rand_fctx;

#define xpfree(var_) \
      do { \
            if (var_ != NULL) \
            { \
                  pfree(var_); \
                  var_ = NULL; \
            } \
      } while (0)

#define xpstrdup(tgtvar_, srcvar_) \
      do { \
            if (srcvar_) \
                  tgtvar_ = pstrdup(srcvar_); \
            else \
                  tgtvar_ = NULL; \
      } while (0)

#define xstreq(tgtvar_, srcvar_) \
      (((tgtvar_ == NULL) && (srcvar_ == NULL)) || \
       ((tgtvar_ != NULL) && (srcvar_ != NULL) && (strcmp(tgtvar_, srcvar_) == 0)))

/* sign, 10 digits, '\0' */
#define INT32_STRLEN    12

/* stored info for a crosstab category */
typedef struct crosstab_cat_desc
{
      char     *catname;            /* full category name */
      int               attidx;                 /* zero based */
} crosstab_cat_desc;

#define MAX_CATNAME_LEN             NAMEDATALEN
#define INIT_CATS                   64

#define crosstab_HashTableLookup(HASHTAB, CATNAME, CATDESC) \
do { \
      crosstab_HashEnt *hentry; char key[MAX_CATNAME_LEN]; \
      \
      MemSet(key, 0, MAX_CATNAME_LEN); \
      snprintf(key, MAX_CATNAME_LEN - 1, "%s", CATNAME); \
      hentry = (crosstab_HashEnt*) hash_search(HASHTAB, \
                                                             key, HASH_FIND, NULL); \
      if (hentry) \
            CATDESC = hentry->catdesc; \
      else \
            CATDESC = NULL; \
} while(0)

#define crosstab_HashTableInsert(HASHTAB, CATDESC) \
do { \
      crosstab_HashEnt *hentry; bool found; char key[MAX_CATNAME_LEN]; \
      \
      MemSet(key, 0, MAX_CATNAME_LEN); \
      snprintf(key, MAX_CATNAME_LEN - 1, "%s", CATDESC->catname); \
      hentry = (crosstab_HashEnt*) hash_search(HASHTAB, \
                                                             key, HASH_ENTER, &found); \
      if (found) \
            ereport(ERROR, \
                        (errcode(ERRCODE_DUPLICATE_OBJECT), \
                         errmsg("duplicate category name"))); \
      hentry->catdesc = CATDESC; \
} while(0)

/* hash table */
typedef struct crosstab_hashent
{
      char        internal_catname[MAX_CATNAME_LEN];
      crosstab_cat_desc *catdesc;
} crosstab_HashEnt;

/*
 * normal_rand - return requested number of random values
 * with a Gaussian (Normal) distribution.
 *
 * inputs are int numvals, float8 mean, and float8 stddev
 * returns setof float8
 */
PG_FUNCTION_INFO_V1(normal_rand);
Datum
normal_rand(PG_FUNCTION_ARGS)
{
      FuncCallContext *funcctx;
      int               call_cntr;
      int               max_calls;
      normal_rand_fctx *fctx;
      float8            mean;
      float8            stddev;
      float8            carry_val;
      bool        use_carry;
      MemoryContext oldcontext;

      /* stuff done only on the first call of the function */
      if (SRF_IS_FIRSTCALL())
      {
            /* create a function context for cross-call persistence */
            funcctx = SRF_FIRSTCALL_INIT();

            /*
             * switch to memory context appropriate for multiple function calls
             */
            oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);

            /* total number of tuples to be returned */
            funcctx->max_calls = PG_GETARG_UINT32(0);

            /* allocate memory for user context */
            fctx = (normal_rand_fctx *) palloc(sizeof(normal_rand_fctx));

            /*
             * Use fctx to keep track of upper and lower bounds from call to call.
             * It will also be used to carry over the spare value we get from the
             * Box-Muller algorithm so that we only actually calculate a new value
             * every other call.
             */
            fctx->mean = PG_GETARG_FLOAT8(1);
            fctx->stddev = PG_GETARG_FLOAT8(2);
            fctx->carry_val = 0;
            fctx->use_carry = false;

            funcctx->user_fctx = fctx;

            MemoryContextSwitchTo(oldcontext);
      }

      /* stuff done on every call of the function */
      funcctx = SRF_PERCALL_SETUP();

      call_cntr = funcctx->call_cntr;
      max_calls = funcctx->max_calls;
      fctx = funcctx->user_fctx;
      mean = fctx->mean;
      stddev = fctx->stddev;
      carry_val = fctx->carry_val;
      use_carry = fctx->use_carry;

      if (call_cntr < max_calls)    /* do when there is more left to send */
      {
            float8            result;

            if (use_carry)
            {
                  /*
                   * reset use_carry and use second value obtained on last pass
                   */
                  fctx->use_carry = false;
                  result = carry_val;
            }
            else
            {
                  float8            normval_1;
                  float8            normval_2;

                  /* Get the next two normal values */
                  get_normal_pair(&normval_1, &normval_2);

                  /* use the first */
                  result = mean + (stddev * normval_1);

                  /* and save the second */
                  fctx->carry_val = mean + (stddev * normval_2);
                  fctx->use_carry = true;
            }

            /* send the result */
            SRF_RETURN_NEXT(funcctx, Float8GetDatum(result));
      }
      else
            /* do when there is no more left */
            SRF_RETURN_DONE(funcctx);
}

/*
 * get_normal_pair()
 * Assigns normally distributed (Gaussian) values to a pair of provided
 * parameters, with mean 0, standard deviation 1.
 *
 * This routine implements Algorithm P (Polar method for normal deviates)
 * from Knuth's _The_Art_of_Computer_Programming_, Volume 2, 3rd ed., pages
 * 122-126. Knuth cites his source as "The polar method", G. E. P. Box, M. E.
 * Muller, and G. Marsaglia, _Annals_Math,_Stat._ 29 (1958), 610-611.
 *
 */
static void
get_normal_pair(float8 *x1, float8 *x2)
{
      float8            u1,
                        u2,
                        v1,
                        v2,
                        s;

      do
      {
            u1 = (float8) random() / (float8) MAX_RANDOM_VALUE;
            u2 = (float8) random() / (float8) MAX_RANDOM_VALUE;

            v1 = (2.0 * u1) - 1.0;
            v2 = (2.0 * u2) - 1.0;

            s = v1 * v1 + v2 * v2;
      } while (s >= 1.0);

      if (s == 0)
      {
            *x1 = 0;
            *x2 = 0;
      }
      else
      {
            s = sqrt((-2.0 * log(s)) / s);
            *x1 = v1 * s;
            *x2 = v2 * s;
      }
}

/*
 * crosstab - create a crosstab of rowids and values columns from a
 * SQL statement returning one rowid column, one category column,
 * and one value column.
 *
 * e.g. given sql which produces:
 *
 *                rowid cat         value
 *                ------+-------+-------
 *                row1  cat1  val1
 *                row1  cat2  val2
 *                row1  cat3  val3
 *                row1  cat4  val4
 *                row2  cat1  val5
 *                row2  cat2  val6
 *                row2  cat3  val7
 *                row2  cat4  val8
 *
 * crosstab returns:
 *                            <===== values columns =====>
 *                rowid cat1  cat2  cat3  cat4
 *                ------+-------+-------+-------+-------
 *                row1  val1  val2  val3  val4
 *                row2  val5  val6  val7  val8
 *
 * NOTES:
 * 1. SQL result must be ordered by 1,2.
 * 2. The number of values columns depends on the tuple description
 *      of the function's declared return type.  The return type's columns
 *      must match the datatypes of the SQL query's result.  The datatype
 *      of the category column can be anything, however.
 * 3. Missing values (i.e. not enough adjacent rows of same rowid to
 *      fill the number of result values columns) are filled in with nulls.
 * 4. Extra values (i.e. too many adjacent rows of same rowid to fill
 *      the number of result values columns) are skipped.
 * 5. Rows with all nulls in the values columns are skipped.
 */
PG_FUNCTION_INFO_V1(crosstab);
Datum
crosstab(PG_FUNCTION_ARGS)
{
      char     *sql = text_to_cstring(PG_GETARG_TEXT_PP(0));
      ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
      Tuplestorestate *tupstore;
      TupleDesc   tupdesc;
      int               call_cntr;
      int               max_calls;
      AttInMetadata *attinmeta;
      SPITupleTable *spi_tuptable;
      TupleDesc   spi_tupdesc;
      bool        firstpass;
      char     *lastrowid;
      int               i;
      int               num_categories;
      MemoryContext per_query_ctx;
      MemoryContext oldcontext;
      int               ret;
      int               proc;

      /* check to see if caller supports us returning a tuplestore */
      if (rsinfo == NULL || !IsA(rsinfo, ReturnSetInfo))
            ereport(ERROR,
                        (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                         errmsg("set-valued function called in context that cannot accept a set")));
      if (!(rsinfo->allowedModes & SFRM_Materialize))
            ereport(ERROR,
                        (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                         errmsg("materialize mode required, but it is not " \
                                    "allowed in this context")));

      per_query_ctx = rsinfo->econtext->ecxt_per_query_memory;

      /* Connect to SPI manager */
      if ((ret = SPI_connect()) < 0)
            /* internal error */
            elog(ERROR, "crosstab: SPI_connect returned %d", ret);

      /* Retrieve the desired rows */
      ret = SPI_execute(sql, true, 0);
      proc = SPI_processed;

      /* If no qualifying tuples, fall out early */
      if (ret != SPI_OK_SELECT || proc <= 0)
      {
            SPI_finish();
            rsinfo->isDone = ExprEndResult;
            PG_RETURN_NULL();
      }

      spi_tuptable = SPI_tuptable;
      spi_tupdesc = spi_tuptable->tupdesc;

      /*----------
       * The provided SQL query must always return three columns.
       *
       * 1. rowname
       *    the label or identifier for each row in the final result
       * 2. category
       *    the label or identifier for each column in the final result
       * 3. values
       *    the value for each column in the final result
       *----------
       */
      if (spi_tupdesc->natts != 3)
            ereport(ERROR,
                        (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                         errmsg("invalid source data SQL statement"),
                         errdetail("The provided SQL must return 3 "
                                       "columns: rowid, category, and values.")));

      /* get a tuple descriptor for our result type */
      switch (get_call_result_type(fcinfo, NULL, &tupdesc))
      {
            case TYPEFUNC_COMPOSITE:
                  /* success */
                  break;
            case TYPEFUNC_RECORD:
                  /* failed to determine actual type of RECORD */
                  ereport(ERROR,
                              (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                               errmsg("function returning record called in context "
                                          "that cannot accept type record")));
                  break;
            default:
                  /* result type isn't composite */
                  elog(ERROR, "return type must be a row type");
                  break;
      }

      /*
       * Check that return tupdesc is compatible with the data we got from SPI,
       * at least based on number and type of attributes
       */
      if (!compatCrosstabTupleDescs(tupdesc, spi_tupdesc))
            ereport(ERROR,
                        (errcode(ERRCODE_SYNTAX_ERROR),
                         errmsg("return and sql tuple descriptions are " \
                                    "incompatible")));

      /*
       * switch to long-lived memory context
       */
      oldcontext = MemoryContextSwitchTo(per_query_ctx);

      /* make sure we have a persistent copy of the result tupdesc */
      tupdesc = CreateTupleDescCopy(tupdesc);

      /* initialize our tuplestore in long-lived context */
      tupstore =
            tuplestore_begin_heap(rsinfo->allowedModes & SFRM_Materialize_Random,
                                            false, work_mem);

      MemoryContextSwitchTo(oldcontext);

      /*
       * Generate attribute metadata needed later to produce tuples from raw C
       * strings
       */
      attinmeta = TupleDescGetAttInMetadata(tupdesc);

      /* total number of tuples to be examined */
      max_calls = proc;

      /* the return tuple always must have 1 rowid + num_categories columns */
      num_categories = tupdesc->natts - 1;

      firstpass = true;
      lastrowid = NULL;

      for (call_cntr = 0; call_cntr < max_calls; call_cntr++)
      {
            bool        skip_tuple = false;
            char    **values;

            /* allocate and zero space */
            values = (char **) palloc0((1 + num_categories) * sizeof(char *));

            /*
             * now loop through the sql results and assign each value in sequence
             * to the next category
             */
            for (i = 0; i < num_categories; i++)
            {
                  HeapTuple   spi_tuple;
                  char     *rowid;

                  /* see if we've gone too far already */
                  if (call_cntr >= max_calls)
                        break;

                  /* get the next sql result tuple */
                  spi_tuple = spi_tuptable->vals[call_cntr];

                  /* get the rowid from the current sql result tuple */
                  rowid = SPI_getvalue(spi_tuple, spi_tupdesc, 1);

                  /*
                   * If this is the first pass through the values for this rowid,
                   * set the first column to rowid
                   */
                  if (i == 0)
                  {
                        xpstrdup(values[0], rowid);

                        /*
                         * Check to see if the rowid is the same as that of the last
                         * tuple sent -- if so, skip this tuple entirely
                         */
                        if (!firstpass && xstreq(lastrowid, rowid))
                        {
                              xpfree(rowid);
                              skip_tuple = true;
                              break;
                        }
                  }

                  /*
                   * If rowid hasn't changed on us, continue building the output
                   * tuple.
                   */
                  if (xstreq(rowid, values[0]))
                  {
                        /*
                         * Get the next category item value, which is always attribute
                         * number three.
                         *
                         * Be careful to assign the value to the array index based on
                         * which category we are presently processing.
                         */
                        values[1 + i] = SPI_getvalue(spi_tuple, spi_tupdesc, 3);

                        /*
                         * increment the counter since we consume a row for each
                         * category, but not for last pass because the outer loop will
                         * do that for us
                         */
                        if (i < (num_categories - 1))
                              call_cntr++;
                        xpfree(rowid);
                  }
                  else
                  {
                        /*
                         * We'll fill in NULLs for the missing values, but we need to
                         * decrement the counter since this sql result row doesn't
                         * belong to the current output tuple.
                         */
                        call_cntr--;
                        xpfree(rowid);
                        break;
                  }
            }

            if (!skip_tuple)
            {
                  HeapTuple   tuple;

                  /* build the tuple and store it */
                  tuple = BuildTupleFromCStrings(attinmeta, values);
                  tuplestore_puttuple(tupstore, tuple);
                  heap_freetuple(tuple);
            }

            /* Remember current rowid */
            xpfree(lastrowid);
            xpstrdup(lastrowid, values[0]);
            firstpass = false;

            /* Clean up */
            for (i = 0; i < num_categories + 1; i++)
                  if (values[i] != NULL)
                        pfree(values[i]);
            pfree(values);
      }

      /* let the caller know we're sending back a tuplestore */
      rsinfo->returnMode = SFRM_Materialize;
      rsinfo->setResult = tupstore;
      rsinfo->setDesc = tupdesc;

      /* release SPI related resources (and return to caller's context) */
      SPI_finish();

      return (Datum) 0;
}

/*
 * crosstab_hash - reimplement crosstab as materialized function and
 * properly deal with missing values (i.e. don't pack remaining
 * values to the left)
 *
 * crosstab - create a crosstab of rowids and values columns from a
 * SQL statement returning one rowid column, one category column,
 * and one value column.
 *
 * e.g. given sql which produces:
 *
 *                rowid cat         value
 *                ------+-------+-------
 *                row1  cat1  val1
 *                row1  cat2  val2
 *                row1  cat4  val4
 *                row2  cat1  val5
 *                row2  cat2  val6
 *                row2  cat3  val7
 *                row2  cat4  val8
 *
 * crosstab returns:
 *                            <===== values columns =====>
 *                rowid cat1  cat2  cat3  cat4
 *                ------+-------+-------+-------+-------
 *                row1  val1  val2  null  val4
 *                row2  val5  val6  val7  val8
 *
 * NOTES:
 * 1. SQL result must be ordered by 1.
 * 2. The number of values columns depends on the tuple description
 *      of the function's declared return type.
 * 3. Missing values (i.e. missing category) are filled in with nulls.
 * 4. Extra values (i.e. not in category results) are skipped.
 */
PG_FUNCTION_INFO_V1(crosstab_hash);
Datum
crosstab_hash(PG_FUNCTION_ARGS)
{
      char     *sql = text_to_cstring(PG_GETARG_TEXT_PP(0));
      char     *cats_sql = text_to_cstring(PG_GETARG_TEXT_PP(1));
      ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
      TupleDesc   tupdesc;
      MemoryContext per_query_ctx;
      MemoryContext oldcontext;
      HTAB     *crosstab_hash;

      /* check to see if caller supports us returning a tuplestore */
      if (rsinfo == NULL || !IsA(rsinfo, ReturnSetInfo))
            ereport(ERROR,
                        (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                         errmsg("set-valued function called in context that cannot accept a set")));
      if (!(rsinfo->allowedModes & SFRM_Materialize) ||
            rsinfo->expectedDesc == NULL)
            ereport(ERROR,
                        (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                         errmsg("materialize mode required, but it is not " \
                                    "allowed in this context")));

      per_query_ctx = rsinfo->econtext->ecxt_per_query_memory;
      oldcontext = MemoryContextSwitchTo(per_query_ctx);

      /* get the requested return tuple description */
      tupdesc = CreateTupleDescCopy(rsinfo->expectedDesc);

      /*
       * Check to make sure we have a reasonable tuple descriptor
       *
       * Note we will attempt to coerce the values into whatever the return
       * attribute type is and depend on the "in" function to complain if
       * needed.
       */
      if (tupdesc->natts < 2)
            ereport(ERROR,
                        (errcode(ERRCODE_SYNTAX_ERROR),
                         errmsg("query-specified return tuple and " \
                                    "crosstab function are not compatible")));

      /* load up the categories hash table */
      crosstab_hash = load_categories_hash(cats_sql, per_query_ctx);

      /* let the caller know we're sending back a tuplestore */
      rsinfo->returnMode = SFRM_Materialize;

      /* now go build it */
      rsinfo->setResult = get_crosstab_tuplestore(sql,
                                                                        crosstab_hash,
                                                                        tupdesc,
                                                                        per_query_ctx,
                                           rsinfo->allowedModes & SFRM_Materialize_Random);

      /*
       * SFRM_Materialize mode expects us to return a NULL Datum. The actual
       * tuples are in our tuplestore and passed back through rsinfo->setResult.
       * rsinfo->setDesc is set to the tuple description that we actually used
       * to build our tuples with, so the caller can verify we did what it was
       * expecting.
       */
      rsinfo->setDesc = tupdesc;
      MemoryContextSwitchTo(oldcontext);

      return (Datum) 0;
}

/*
 * load up the categories hash table
 */
static HTAB *
load_categories_hash(char *cats_sql, MemoryContext per_query_ctx)
{
      HTAB     *crosstab_hash;
      HASHCTL           ctl;
      int               ret;
      int               proc;
      MemoryContext SPIcontext;

      /* initialize the category hash table */
      MemSet(&ctl, 0, sizeof(ctl));
      ctl.keysize = MAX_CATNAME_LEN;
      ctl.entrysize = sizeof(crosstab_HashEnt);
      ctl.hcxt = per_query_ctx;

      /*
       * use INIT_CATS, defined above as a guess of how many hash table entries
       * to create, initially
       */
      crosstab_hash = hash_create("crosstab hash",
                                                INIT_CATS,
                                                &ctl,
                                                HASH_ELEM | HASH_CONTEXT);

      /* Connect to SPI manager */
      if ((ret = SPI_connect()) < 0)
            /* internal error */
            elog(ERROR, "load_categories_hash: SPI_connect returned %d", ret);

      /* Retrieve the category name rows */
      ret = SPI_execute(cats_sql, true, 0);
      proc = SPI_processed;

      /* Check for qualifying tuples */
      if ((ret == SPI_OK_SELECT) && (proc > 0))
      {
            SPITupleTable *spi_tuptable = SPI_tuptable;
            TupleDesc   spi_tupdesc = spi_tuptable->tupdesc;
            int               i;

            /*
             * The provided categories SQL query must always return one column:
             * category - the label or identifier for each column
             */
            if (spi_tupdesc->natts != 1)
                  ereport(ERROR,
                              (errcode(ERRCODE_SYNTAX_ERROR),
                               errmsg("provided \"categories\" SQL must " \
                                          "return 1 column of at least one row")));

            for (i = 0; i < proc; i++)
            {
                  crosstab_cat_desc *catdesc;
                  char     *catname;
                  HeapTuple   spi_tuple;

                  /* get the next sql result tuple */
                  spi_tuple = spi_tuptable->vals[i];

                  /* get the category from the current sql result tuple */
                  catname = SPI_getvalue(spi_tuple, spi_tupdesc, 1);

                  SPIcontext = MemoryContextSwitchTo(per_query_ctx);

                  catdesc = (crosstab_cat_desc *) palloc(sizeof(crosstab_cat_desc));
                  catdesc->catname = catname;
                  catdesc->attidx = i;

                  /* Add the proc description block to the hashtable */
                  crosstab_HashTableInsert(crosstab_hash, catdesc);

                  MemoryContextSwitchTo(SPIcontext);
            }
      }

      if (SPI_finish() != SPI_OK_FINISH)
            /* internal error */
            elog(ERROR, "load_categories_hash: SPI_finish() failed");

      return crosstab_hash;
}

/*
 * create and populate the crosstab tuplestore using the provided source query
 */
static Tuplestorestate *
get_crosstab_tuplestore(char *sql,
                                    HTAB *crosstab_hash,
                                    TupleDesc tupdesc,
                                    MemoryContext per_query_ctx,
                                    bool randomAccess)
{
      Tuplestorestate *tupstore;
      int               num_categories = hash_get_num_entries(crosstab_hash);
      AttInMetadata *attinmeta = TupleDescGetAttInMetadata(tupdesc);
      char    **values;
      HeapTuple   tuple;
      int               ret;
      int               proc;

      /* initialize our tuplestore (while still in query context!) */
      tupstore = tuplestore_begin_heap(randomAccess, false, work_mem);

      /* Connect to SPI manager */
      if ((ret = SPI_connect()) < 0)
            /* internal error */
            elog(ERROR, "get_crosstab_tuplestore: SPI_connect returned %d", ret);

      /* Now retrieve the crosstab source rows */
      ret = SPI_execute(sql, true, 0);
      proc = SPI_processed;

      /* Check for qualifying tuples */
      if ((ret == SPI_OK_SELECT) && (proc > 0))
      {
            SPITupleTable *spi_tuptable = SPI_tuptable;
            TupleDesc   spi_tupdesc = spi_tuptable->tupdesc;
            int               ncols = spi_tupdesc->natts;
            char     *rowid;
            char     *lastrowid = NULL;
            bool        firstpass = true;
            int               i,
                              j;
            int               result_ncols;

            if (num_categories == 0)
            {
                  /* no qualifying category tuples */
                  ereport(ERROR,
                              (errcode(ERRCODE_SYNTAX_ERROR),
                               errmsg("provided \"categories\" SQL must " \
                                          "return 1 column of at least one row")));
            }

            /*
             * The provided SQL query must always return at least three columns:
             *
             * 1. rowname     the label for each row - column 1 in the final result
             * 2. category    the label for each value-column in the final result 3.
             * value     the values used to populate the value-columns
             *
             * If there are more than three columns, the last two are taken as
             * "category" and "values". The first column is taken as "rowname".
             * Additional columns (2 thru N-2) are assumed the same for the same
             * "rowname", and are copied into the result tuple from the first time
             * we encounter a particular rowname.
             */
            if (ncols < 3)
                  ereport(ERROR,
                              (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                               errmsg("invalid source data SQL statement"),
                               errdetail("The provided SQL must return 3 " \
                                             " columns; rowid, category, and values.")));

            result_ncols = (ncols - 2) + num_categories;

            /* Recheck to make sure we tuple descriptor still looks reasonable */
            if (tupdesc->natts != result_ncols)
                  ereport(ERROR,
                              (errcode(ERRCODE_SYNTAX_ERROR),
                               errmsg("invalid return type"),
                               errdetail("Query-specified return " \
                                             "tuple has %d columns but crosstab " \
                                             "returns %d.", tupdesc->natts, result_ncols)));

            /* allocate space */
            values = (char **) palloc(result_ncols * sizeof(char *));

            /* and make sure it's clear */
            memset(values, '\0', result_ncols * sizeof(char *));

            for (i = 0; i < proc; i++)
            {
                  HeapTuple   spi_tuple;
                  crosstab_cat_desc *catdesc;
                  char     *catname;

                  /* get the next sql result tuple */
                  spi_tuple = spi_tuptable->vals[i];

                  /* get the rowid from the current sql result tuple */
                  rowid = SPI_getvalue(spi_tuple, spi_tupdesc, 1);

                  /*
                   * if we're on a new output row, grab the column values up to
                   * column N-2 now
                   */
                  if (firstpass || !xstreq(lastrowid, rowid))
                  {
                        /*
                         * a new row means we need to flush the old one first, unless
                         * we're on the very first row
                         */
                        if (!firstpass)
                        {
                              /* rowid changed, flush the previous output row */
                              tuple = BuildTupleFromCStrings(attinmeta, values);

                              tuplestore_puttuple(tupstore, tuple);

                              for (j = 0; j < result_ncols; j++)
                                    xpfree(values[j]);
                        }

                        values[0] = rowid;
                        for (j = 1; j < ncols - 2; j++)
                              values[j] = SPI_getvalue(spi_tuple, spi_tupdesc, j + 1);

                        /* we're no longer on the first pass */
                        firstpass = false;
                  }

                  /* look up the category and fill in the appropriate column */
                  catname = SPI_getvalue(spi_tuple, spi_tupdesc, ncols - 1);

                  if (catname != NULL)
                  {
                        crosstab_HashTableLookup(crosstab_hash, catname, catdesc);

                        if (catdesc)
                              values[catdesc->attidx + ncols - 2] =
                                    SPI_getvalue(spi_tuple, spi_tupdesc, ncols);
                  }

                  xpfree(lastrowid);
                  xpstrdup(lastrowid, rowid);
            }

            /* flush the last output row */
            tuple = BuildTupleFromCStrings(attinmeta, values);

            tuplestore_puttuple(tupstore, tuple);
      }

      if (SPI_finish() != SPI_OK_FINISH)
            /* internal error */
            elog(ERROR, "get_crosstab_tuplestore: SPI_finish() failed");

      tuplestore_donestoring(tupstore);

      return tupstore;
}

/*
 * connectby_text - produce a result set from a hierarchical (parent/child)
 * table.
 *
 * e.g. given table foo:
 *
 *                keyid parent_keyid pos
 *                ------+------------+--
 *                row1  NULL         0
 *                row2  row1         0
 *                row3  row1         0
 *                row4  row2         1
 *                row5  row2         0
 *                row6  row4         0
 *                row7  row3         0
 *                row8  row6         0
 *                row9  row5         0
 *
 *
 * connectby(text relname, text keyid_fld, text parent_keyid_fld
 *                  [, text orderby_fld], text start_with, int max_depth
 *                  [, text branch_delim])
 * connectby('foo', 'keyid', 'parent_keyid', 'pos', 'row2', 0, '~') returns:
 *
 *          keyid parent_id   level  branch                       serial
 *          ------+-----------+--------+-----------------------
 *          row2  NULL          0           row2                          1
 *          row5  row2          1           row2~row5               2
 *          row9  row5          2           row2~row5~row9    3
 *          row4  row2          1           row2~row4               4
 *          row6  row4          2           row2~row4~row6    5
 *          row8  row6          3           row2~row4~row6~row8 6
 *
 */
PG_FUNCTION_INFO_V1(connectby_text);

#define CONNECTBY_NCOLS                         4
#define CONNECTBY_NCOLS_NOBRANCH          3

Datum
connectby_text(PG_FUNCTION_ARGS)
{
      char     *relname = text_to_cstring(PG_GETARG_TEXT_PP(0));
      char     *key_fld = text_to_cstring(PG_GETARG_TEXT_PP(1));
      char     *parent_key_fld = text_to_cstring(PG_GETARG_TEXT_PP(2));
      char     *start_with = text_to_cstring(PG_GETARG_TEXT_PP(3));
      int               max_depth = PG_GETARG_INT32(4);
      char     *branch_delim = NULL;
      bool        show_branch = false;
      bool        show_serial = false;
      ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
      TupleDesc   tupdesc;
      AttInMetadata *attinmeta;
      MemoryContext per_query_ctx;
      MemoryContext oldcontext;

      /* check to see if caller supports us returning a tuplestore */
      if (rsinfo == NULL || !IsA(rsinfo, ReturnSetInfo))
            ereport(ERROR,
                        (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                         errmsg("set-valued function called in context that cannot accept a set")));
      if (!(rsinfo->allowedModes & SFRM_Materialize) ||
            rsinfo->expectedDesc == NULL)
            ereport(ERROR,
                        (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                         errmsg("materialize mode required, but it is not " \
                                    "allowed in this context")));

      if (fcinfo->nargs == 6)
      {
            branch_delim = text_to_cstring(PG_GETARG_TEXT_PP(5));
            show_branch = true;
      }
      else
            /* default is no show, tilde for the delimiter */
            branch_delim = pstrdup("~");

      per_query_ctx = rsinfo->econtext->ecxt_per_query_memory;
      oldcontext = MemoryContextSwitchTo(per_query_ctx);

      /* get the requested return tuple description */
      tupdesc = CreateTupleDescCopy(rsinfo->expectedDesc);

      /* does it meet our needs */
      validateConnectbyTupleDesc(tupdesc, show_branch, show_serial);

      /* OK, use it then */
      attinmeta = TupleDescGetAttInMetadata(tupdesc);

      /* OK, go to work */
      rsinfo->returnMode = SFRM_Materialize;
      rsinfo->setResult = connectby(relname,
                                                  key_fld,
                                                  parent_key_fld,
                                                  NULL,
                                                  branch_delim,
                                                  start_with,
                                                  max_depth,
                                                  show_branch,
                                                  show_serial,
                                                  per_query_ctx,
                                            rsinfo->allowedModes & SFRM_Materialize_Random,
                                                  attinmeta);
      rsinfo->setDesc = tupdesc;

      MemoryContextSwitchTo(oldcontext);

      /*
       * SFRM_Materialize mode expects us to return a NULL Datum. The actual
       * tuples are in our tuplestore and passed back through rsinfo->setResult.
       * rsinfo->setDesc is set to the tuple description that we actually used
       * to build our tuples with, so the caller can verify we did what it was
       * expecting.
       */
      return (Datum) 0;
}

PG_FUNCTION_INFO_V1(connectby_text_serial);
Datum
connectby_text_serial(PG_FUNCTION_ARGS)
{
      char     *relname = text_to_cstring(PG_GETARG_TEXT_PP(0));
      char     *key_fld = text_to_cstring(PG_GETARG_TEXT_PP(1));
      char     *parent_key_fld = text_to_cstring(PG_GETARG_TEXT_PP(2));
      char     *orderby_fld = text_to_cstring(PG_GETARG_TEXT_PP(3));
      char     *start_with = text_to_cstring(PG_GETARG_TEXT_PP(4));
      int               max_depth = PG_GETARG_INT32(5);
      char     *branch_delim = NULL;
      bool        show_branch = false;
      bool        show_serial = true;
      ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
      TupleDesc   tupdesc;
      AttInMetadata *attinmeta;
      MemoryContext per_query_ctx;
      MemoryContext oldcontext;

      /* check to see if caller supports us returning a tuplestore */
      if (rsinfo == NULL || !IsA(rsinfo, ReturnSetInfo))
            ereport(ERROR,
                        (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                         errmsg("set-valued function called in context that cannot accept a set")));
      if (!(rsinfo->allowedModes & SFRM_Materialize) ||
            rsinfo->expectedDesc == NULL)
            ereport(ERROR,
                        (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                         errmsg("materialize mode required, but it is not " \
                                    "allowed in this context")));

      if (fcinfo->nargs == 7)
      {
            branch_delim = text_to_cstring(PG_GETARG_TEXT_PP(6));
            show_branch = true;
      }
      else
            /* default is no show, tilde for the delimiter */
            branch_delim = pstrdup("~");

      per_query_ctx = rsinfo->econtext->ecxt_per_query_memory;
      oldcontext = MemoryContextSwitchTo(per_query_ctx);

      /* get the requested return tuple description */
      tupdesc = CreateTupleDescCopy(rsinfo->expectedDesc);

      /* does it meet our needs */
      validateConnectbyTupleDesc(tupdesc, show_branch, show_serial);

      /* OK, use it then */
      attinmeta = TupleDescGetAttInMetadata(tupdesc);

      /* OK, go to work */
      rsinfo->returnMode = SFRM_Materialize;
      rsinfo->setResult = connectby(relname,
                                                  key_fld,
                                                  parent_key_fld,
                                                  orderby_fld,
                                                  branch_delim,
                                                  start_with,
                                                  max_depth,
                                                  show_branch,
                                                  show_serial,
                                                  per_query_ctx,
                                            rsinfo->allowedModes & SFRM_Materialize_Random,
                                                  attinmeta);
      rsinfo->setDesc = tupdesc;

      MemoryContextSwitchTo(oldcontext);

      /*
       * SFRM_Materialize mode expects us to return a NULL Datum. The actual
       * tuples are in our tuplestore and passed back through rsinfo->setResult.
       * rsinfo->setDesc is set to the tuple description that we actually used
       * to build our tuples with, so the caller can verify we did what it was
       * expecting.
       */
      return (Datum) 0;
}


/*
 * connectby - does the real work for connectby_text()
 */
static Tuplestorestate *
connectby(char *relname,
              char *key_fld,
              char *parent_key_fld,
              char *orderby_fld,
              char *branch_delim,
              char *start_with,
              int max_depth,
              bool show_branch,
              bool show_serial,
              MemoryContext per_query_ctx,
              bool randomAccess,
              AttInMetadata *attinmeta)
{
      Tuplestorestate *tupstore = NULL;
      int               ret;
      MemoryContext oldcontext;

      int               serial = 1;

      /* Connect to SPI manager */
      if ((ret = SPI_connect()) < 0)
            /* internal error */
            elog(ERROR, "connectby: SPI_connect returned %d", ret);

      /* switch to longer term context to create the tuple store */
      oldcontext = MemoryContextSwitchTo(per_query_ctx);

      /* initialize our tuplestore */
      tupstore = tuplestore_begin_heap(randomAccess, false, work_mem);

      MemoryContextSwitchTo(oldcontext);

      /* now go get the whole tree */
      tupstore = build_tuplestore_recursively(key_fld,
                                                                  parent_key_fld,
                                                                  relname,
                                                                  orderby_fld,
                                                                  branch_delim,
                                                                  start_with,
                                                                  start_with, /* current_branch */
                                                                  0,    /* initial level is 0 */
                                                                  &serial,    /* initial serial is 1 */
                                                                  max_depth,
                                                                  show_branch,
                                                                  show_serial,
                                                                  per_query_ctx,
                                                                  attinmeta,
                                                                  tupstore);

      SPI_finish();

      return tupstore;
}

static Tuplestorestate *
build_tuplestore_recursively(char *key_fld,
                                           char *parent_key_fld,
                                           char *relname,
                                           char *orderby_fld,
                                           char *branch_delim,
                                           char *start_with,
                                           char *branch,
                                           int level,
                                           int *serial,
                                           int max_depth,
                                           bool show_branch,
                                           bool show_serial,
                                           MemoryContext per_query_ctx,
                                           AttInMetadata *attinmeta,
                                           Tuplestorestate *tupstore)
{
      TupleDesc   tupdesc = attinmeta->tupdesc;
      int               ret;
      int               proc;
      int               serial_column;
      StringInfoData sql;
      char    **values;
      char     *current_key;
      char     *current_key_parent;
      char        current_level[INT32_STRLEN];
      char        serial_str[INT32_STRLEN];
      char     *current_branch;
      HeapTuple   tuple;

      if (max_depth > 0 && level > max_depth)
            return tupstore;

      initStringInfo(&sql);

      /* Build initial sql statement */
      if (!show_serial)
      {
            appendStringInfo(&sql, "SELECT %s, %s FROM %s WHERE %s = %s AND %s IS NOT NULL AND %s <> %s",
                                     key_fld,
                                     parent_key_fld,
                                     relname,
                                     parent_key_fld,
                                     quote_literal_cstr(start_with),
                                     key_fld, key_fld, parent_key_fld);
            serial_column = 0;
      }
      else
      {
            appendStringInfo(&sql, "SELECT %s, %s FROM %s WHERE %s = %s AND %s IS NOT NULL AND %s <> %s ORDER BY %s",
                                     key_fld,
                                     parent_key_fld,
                                     relname,
                                     parent_key_fld,
                                     quote_literal_cstr(start_with),
                                     key_fld, key_fld, parent_key_fld,
                                     orderby_fld);
            serial_column = 1;
      }

      if (show_branch)
            values = (char **) palloc((CONNECTBY_NCOLS + serial_column) * sizeof(char *));
      else
            values = (char **) palloc((CONNECTBY_NCOLS_NOBRANCH + serial_column) * sizeof(char *));

      /* First time through, do a little setup */
      if (level == 0)
      {
            /* root value is the one we initially start with */
            values[0] = start_with;

            /* root value has no parent */
            values[1] = NULL;

            /* root level is 0 */
            sprintf(current_level, "%d", level);
            values[2] = current_level;

            /* root branch is just starting root value */
            if (show_branch)
                  values[3] = start_with;

            /* root starts the serial with 1 */
            if (show_serial)
            {
                  sprintf(serial_str, "%d", (*serial)++);
                  if (show_branch)
                        values[4] = serial_str;
                  else
                        values[3] = serial_str;
            }

            /* construct the tuple */
            tuple = BuildTupleFromCStrings(attinmeta, values);

            /* now store it */
            tuplestore_puttuple(tupstore, tuple);

            /* increment level */
            level++;
      }

      /* Retrieve the desired rows */
      ret = SPI_execute(sql.data, true, 0);
      proc = SPI_processed;

      /* Check for qualifying tuples */
      if ((ret == SPI_OK_SELECT) && (proc > 0))
      {
            HeapTuple   spi_tuple;
            SPITupleTable *tuptable = SPI_tuptable;
            TupleDesc   spi_tupdesc = tuptable->tupdesc;
            int               i;
            StringInfoData branchstr;
            StringInfoData chk_branchstr;
            StringInfoData chk_current_key;

            /* First time through, do a little more setup */
            if (level == 0)
            {
                  /*
                   * Check that return tupdesc is compatible with the one we got
                   * from the query, but only at level 0 -- no need to check more
                   * than once
                   */

                  if (!compatConnectbyTupleDescs(tupdesc, spi_tupdesc))
                        ereport(ERROR,
                                    (errcode(ERRCODE_SYNTAX_ERROR),
                                     errmsg("invalid return type"),
                                     errdetail("Return and SQL tuple descriptions are " \
                                                   "incompatible.")));
            }

            initStringInfo(&branchstr);
            initStringInfo(&chk_branchstr);
            initStringInfo(&chk_current_key);

            for (i = 0; i < proc; i++)
            {
                  /* initialize branch for this pass */
                  appendStringInfo(&branchstr, "%s", branch);
                  appendStringInfo(&chk_branchstr, "%s%s%s", branch_delim, branch, branch_delim);

                  /* get the next sql result tuple */
                  spi_tuple = tuptable->vals[i];

                  /* get the current key and parent */
                  current_key = SPI_getvalue(spi_tuple, spi_tupdesc, 1);
                  appendStringInfo(&chk_current_key, "%s%s%s", branch_delim, current_key, branch_delim);
                  current_key_parent = pstrdup(SPI_getvalue(spi_tuple, spi_tupdesc, 2));

                  /* get the current level */
                  sprintf(current_level, "%d", level);

                  /* check to see if this key is also an ancestor */
                  if (strstr(chk_branchstr.data, chk_current_key.data))
                        elog(ERROR, "infinite recursion detected");

                  /* OK, extend the branch */
                  appendStringInfo(&branchstr, "%s%s", branch_delim, current_key);
                  current_branch = branchstr.data;

                  /* build a tuple */
                  values[0] = pstrdup(current_key);
                  values[1] = current_key_parent;
                  values[2] = current_level;
                  if (show_branch)
                        values[3] = current_branch;
                  if (show_serial)
                  {
                        sprintf(serial_str, "%d", (*serial)++);
                        if (show_branch)
                              values[4] = serial_str;
                        else
                              values[3] = serial_str;
                  }

                  tuple = BuildTupleFromCStrings(attinmeta, values);

                  xpfree(current_key);
                  xpfree(current_key_parent);

                  /* store the tuple for later use */
                  tuplestore_puttuple(tupstore, tuple);

                  heap_freetuple(tuple);

                  /* recurse using current_key_parent as the new start_with */
                  tupstore = build_tuplestore_recursively(key_fld,
                                                                              parent_key_fld,
                                                                              relname,
                                                                              orderby_fld,
                                                                              branch_delim,
                                                                              values[0],
                                                                              current_branch,
                                                                              level + 1,
                                                                              serial,
                                                                              max_depth,
                                                                              show_branch,
                                                                              show_serial,
                                                                              per_query_ctx,
                                                                              attinmeta,
                                                                              tupstore);

                  /* reset branch for next pass */
                  resetStringInfo(&branchstr);
                  resetStringInfo(&chk_branchstr);
                  resetStringInfo(&chk_current_key);
            }

            xpfree(branchstr.data);
            xpfree(chk_branchstr.data);
            xpfree(chk_current_key.data);
      }

      return tupstore;
}

/*
 * Check expected (query runtime) tupdesc suitable for Connectby
 */
static void
validateConnectbyTupleDesc(TupleDesc tupdesc, bool show_branch, bool show_serial)
{
      int               serial_column = 0;

      if (show_serial)
            serial_column = 1;

      /* are there the correct number of columns */
      if (show_branch)
      {
            if (tupdesc->natts != (CONNECTBY_NCOLS + serial_column))
                  ereport(ERROR,
                              (errcode(ERRCODE_SYNTAX_ERROR),
                               errmsg("invalid return type"),
                               errdetail("Query-specified return tuple has " \
                                             "wrong number of columns.")));
      }
      else
      {
            if (tupdesc->natts != CONNECTBY_NCOLS_NOBRANCH + serial_column)
                  ereport(ERROR,
                              (errcode(ERRCODE_SYNTAX_ERROR),
                               errmsg("invalid return type"),
                               errdetail("Query-specified return tuple has " \
                                             "wrong number of columns.")));
      }

      /* check that the types of the first two columns match */
      if (tupdesc->attrs[0]->atttypid != tupdesc->attrs[1]->atttypid)
            ereport(ERROR,
                        (errcode(ERRCODE_SYNTAX_ERROR),
                         errmsg("invalid return type"),
                         errdetail("First two columns must be the same type.")));

      /* check that the type of the third column is INT4 */
      if (tupdesc->attrs[2]->atttypid != INT4OID)
            ereport(ERROR,
                        (errcode(ERRCODE_SYNTAX_ERROR),
                         errmsg("invalid return type"),
                         errdetail("Third column must be type %s.",
                                       format_type_be(INT4OID))));

      /* check that the type of the fourth column is TEXT if applicable */
      if (show_branch && tupdesc->attrs[3]->atttypid != TEXTOID)
            ereport(ERROR,
                        (errcode(ERRCODE_SYNTAX_ERROR),
                         errmsg("invalid return type"),
                         errdetail("Fourth column must be type %s.",
                                       format_type_be(TEXTOID))));

      /* check that the type of the fifth column is INT4 */
      if (show_branch && show_serial && tupdesc->attrs[4]->atttypid != INT4OID)
            elog(ERROR, "query-specified return tuple not valid for Connectby: "
                   "fifth column must be type %s", format_type_be(INT4OID));

      /* check that the type of the fifth column is INT4 */
      if (!show_branch && show_serial && tupdesc->attrs[3]->atttypid != INT4OID)
            elog(ERROR, "query-specified return tuple not valid for Connectby: "
                   "fourth column must be type %s", format_type_be(INT4OID));

      /* OK, the tupdesc is valid for our purposes */
}

/*
 * Check if spi sql tupdesc and return tupdesc are compatible
 */
static bool
compatConnectbyTupleDescs(TupleDesc ret_tupdesc, TupleDesc sql_tupdesc)
{
      Oid               ret_atttypid;
      Oid               sql_atttypid;

      /* check the key_fld types match */
      ret_atttypid = ret_tupdesc->attrs[0]->atttypid;
      sql_atttypid = sql_tupdesc->attrs[0]->atttypid;
      if (ret_atttypid != sql_atttypid)
            ereport(ERROR,
                        (errcode(ERRCODE_SYNTAX_ERROR),
                         errmsg("invalid return type"),
                         errdetail("SQL key field datatype does " \
                                       "not match return key field datatype.")));

      /* check the parent_key_fld types match */
      ret_atttypid = ret_tupdesc->attrs[1]->atttypid;
      sql_atttypid = sql_tupdesc->attrs[1]->atttypid;
      if (ret_atttypid != sql_atttypid)
            ereport(ERROR,
                        (errcode(ERRCODE_SYNTAX_ERROR),
                         errmsg("invalid return type"),
                         errdetail("SQL parent key field datatype does " \
                                       "not match return parent key field datatype.")));

      /* OK, the two tupdescs are compatible for our purposes */
      return true;
}

/*
 * Check if two tupdescs match in type of attributes
 */
static bool
compatCrosstabTupleDescs(TupleDesc ret_tupdesc, TupleDesc sql_tupdesc)
{
      int               i;
      Form_pg_attribute ret_attr;
      Oid               ret_atttypid;
      Form_pg_attribute sql_attr;
      Oid               sql_atttypid;

      if (ret_tupdesc->natts < 2 ||
            sql_tupdesc->natts < 3)
            return false;

      /* check the rowid types match */
      ret_atttypid = ret_tupdesc->attrs[0]->atttypid;
      sql_atttypid = sql_tupdesc->attrs[0]->atttypid;
      if (ret_atttypid != sql_atttypid)
            ereport(ERROR,
                        (errcode(ERRCODE_SYNTAX_ERROR),
                         errmsg("invalid return type"),
                         errdetail("SQL rowid datatype does not match " \
                                       "return rowid datatype.")));

      /*
       * - attribute [1] of the sql tuple is the category; no need to check it -
       * attribute [2] of the sql tuple should match attributes [1] to [natts]
       * of the return tuple
       */
      sql_attr = sql_tupdesc->attrs[2];
      for (i = 1; i < ret_tupdesc->natts; i++)
      {
            ret_attr = ret_tupdesc->attrs[i];

            if (ret_attr->atttypid != sql_attr->atttypid)
                  return false;
      }

      /* OK, the two tupdescs are compatible for our purposes */
      return true;
}

/*
 * Return a properly quoted literal value.
 * Uses quote_literal in quote.c
 */
static char *
quote_literal_cstr(char *rawstr)
{
      text     *rawstr_text;
      text     *result_text;
      char     *result;

      rawstr_text = cstring_to_text(rawstr);
      result_text = DatumGetTextP(DirectFunctionCall1(quote_literal,
                                                                    PointerGetDatum(rawstr_text)));
      result = text_to_cstring(result_text);

      return result;
}

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