Error: rows returned by function are not all of the same row type

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Error: rows returned by function are not all of the same row type

andrey.sychev
Hi, everyone,

I have written C-language function that returns
multiple composite rows.

Generally function works as expected, but sometimes problem takes place.
At  rough  guess  the  problem  occurs  when  number of returning rows
relatively large (more than 100K - 1M).

I have added some checkpoints.
P5 and P6 are present in snippet.

The  function  always  reaches checkpoint P5, but before P6 it returns
error:

"rows returned by function are not all of the same row type"

Supposedly, at some iteration on SRF_RETURN_NEXT

Any ideas?

Below is a snippet of code:

#include "postgres.h"
#include "funcapi.h"
#include "executor/spi.h"

Datum my_func(PG_FUNCTION_ARGS);

PG_FUNCTION_INFO_V1(show_eudc);

Datum
my_eudc(PG_FUNCTION_ARGS)
{
  FuncCallContext     *funcctx;
  int                  call_cntr;
  int                  max_calls;
  TupleDesc   tupleDesc;

  /* Build a tuple descriptor for our result type */
  if(get_call_result_type(fcinfo, NULL, &tupleDesc) != TYPEFUNC_COMPOSITE)
  {
    ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), errmsg("Function returning record called in context that cannot accept type record")));
  }

  if(SRF_IS_FIRSTCALL())
  {
    MemoryContext oldcontext;
    funcctx = SRF_FIRSTCALL_INIT();
    oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);

    My_SPI_call_context ctx;
    memset(&ctx, 0, sizeof(My_SPI_call_context));

    int ret;

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

    /* some setup code */

    const char* stSQLDef_0[1] = {
    "CREATE TEMPORARY TABLE results (v1 BIGINT NOT NULL, v2 INTEGER NOT NULL)",
    };

    for(int k=0; k<1; k++)
    {
      ret = SPI_exec(stSQLDef_0[k], 0);
      if(ret != SPI_OK_UTILITY)
      {
        elog(ERROR, "SPI_exec (0)-(%d) returned %d", k, ret);
        my_spi_free_context(&ctx);
        PG_RETURN_VOID();
      }
    }

    /* many code */

    const char* stSQLResultsInsert = "INSERT INTO results (v1, v2) VALUES (%ld, %d)";
   
    for(int k=0; k<N; k++)
    {
      memset(ctx.stSQL, 0, SQL_BUFFER_LENGTH * sizeof(char));
      sprintf(ctx.stSQL, stSQLResultsInsert, v1, v2);
      ret = SPI_exec(ctx.stSQL, 0);
      proc_0 = SPI_processed;
      if(ret != SPI_OK_INSERT || proc_0 <= 0)
      {
        elog(ERROR, "spi_match: SPI_execute (8_H) returned %d", ret);
        my_spi_free_context(&ctx);
        PG_RETURN_VOID();
      }
    }

    /* some code with aggregation of data from TEMP TABLE results */

    memset(ctx.stSQL, 0, SQL_BUFFER_LENGTH * sizeof(char));
    sprintf(ctx.stSQL, "SELECT v1, v2 FROM results");
    ret = SPI_execute(ctx.stSQL, false, 0);
    proc = SPI_processed;

    ereport(NOTICE, (errmsg("P5: [%s]-(%d)", (const char*)__FUNCTION__, proc)));

    if(ret != SPI_OK_SELECT || proc <= 0)
    {
      funcctx->max_calls = 0;
      funcctx->user_fctx = NULL;
      if(proc <= 0) ereport(NOTICE, (errmsg("SPI_execute (10) returned %d", ret)));
    }
    else if(proc)
    {
      spi_tuptable = SPI_tuptable;

      funcctx->max_calls = proc;
      funcctx->user_fctx = spi_tuptable;
    }

    my_spi_free_context(&ctx);

    tupleDesc = BlessTupleDesc(tupleDesc);
    funcctx->tuple_desc = tupleDesc;
    MemoryContextSwitchTo(oldcontext);

  }

  funcctx = SRF_PERCALL_SETUP();

  call_cntr = funcctx->call_cntr;
  max_calls = funcctx->max_calls;

  if(call_cntr < max_calls)
  {
    SPITupleTable* table = (SPITupleTable*)funcctx->user_fctx;
    Datum       results; /* Results tuple */
    Datum       column[2];
    bool        isColumnNull[2];
    HeapTuple   tuple;
    int m;

    if(table)
    {
      for(m=0; m<2; m++)
      {
        column[m] = SPI_getbinval(table->vals[call_cntr], table->tupdesc, m+1, &isColumnNull[m]);
      }

      tuple = heap_form_tuple(funcctx->tuple_desc, column, isColumnNull);
      results = HeapTupleGetDatum(tuple);
      SRF_RETURN_NEXT(funcctx, results);
    }
  }
  else
  {
    int ret;
    SPITupleTable* table = (SPITupleTable*)funcctx->user_fctx;
    if(table)
    {
      SPI_freetuptable(table);
    }

    ereport(NOTICE, (errmsg("P6: [%s]-(%d)", (const char*)__FUNCTION__, max_calls)));

    ret = SPI_exec("DROP TABLE results", 0);
    if(ret != SPI_OK_UTILITY)
    {
      elog(ERROR, "spi_match: SPI_exec (20) returned %d", ret);
    }

    SPI_finish();
    SRF_RETURN_DONE(funcctx);
  }

  PG_RETURN_VOID();
}

--
Best regards,

Andrey Sychev

[hidden email]



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Re: Error: rows returned by function are not all of the same row type

Ed Behn
I took at cursory look at your function I didn't notice anything obviously wrong. I have, however, encountered a similar problem with my own C code in the past. It would work fine for some number of rows and then not. 

I don't recall the precise bug. The broad stroke was that I was assuming a memory location would be static from one call to the next. It was for a while but at some point, postgres would move it. I had to be sure to get the location from the appropriate macro with each call instead of simply retaining my own point from one call to the next. 

I don't know if that may be the problem you are encountering. 
           -Ed

On Thu, Jul 4, 2019 at 5:36 AM <[hidden email]> wrote:
Hi, everyone,

I have written C-language function that returns
multiple composite rows.

Generally function works as expected, but sometimes problem takes place.
At  rough  guess  the  problem  occurs  when  number of returning rows
relatively large (more than 100K - 1M).

I have added some checkpoints.
P5 and P6 are present in snippet.

The  function  always  reaches checkpoint P5, but before P6 it returns
error:

"rows returned by function are not all of the same row type"

Supposedly, at some iteration on SRF_RETURN_NEXT

Any ideas?

Below is a snippet of code:

#include "postgres.h"
#include "funcapi.h"
#include "executor/spi.h"

Datum my_func(PG_FUNCTION_ARGS);

PG_FUNCTION_INFO_V1(show_eudc);

Datum
my_eudc(PG_FUNCTION_ARGS)
{
  FuncCallContext     *funcctx;
  int                  call_cntr;
  int                  max_calls;
  TupleDesc   tupleDesc;

  /* Build a tuple descriptor for our result type */
  if(get_call_result_type(fcinfo, NULL, &tupleDesc) != TYPEFUNC_COMPOSITE)
  {
    ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), errmsg("Function returning record called in context that cannot accept type record")));
  }

  if(SRF_IS_FIRSTCALL())
  {
    MemoryContext oldcontext;
    funcctx = SRF_FIRSTCALL_INIT();
    oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);

    My_SPI_call_context ctx;
    memset(&ctx, 0, sizeof(My_SPI_call_context));

    int ret;

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

    /* some setup code */

    const char* stSQLDef_0[1] = {
    "CREATE TEMPORARY TABLE results (v1 BIGINT NOT NULL, v2 INTEGER NOT NULL)",
    };

    for(int k=0; k<1; k++)
    {
      ret = SPI_exec(stSQLDef_0[k], 0);
      if(ret != SPI_OK_UTILITY)
      {
        elog(ERROR, "SPI_exec (0)-(%d) returned %d", k, ret);
        my_spi_free_context(&ctx);
        PG_RETURN_VOID();
      }
    }

    /* many code */

    const char* stSQLResultsInsert = "INSERT INTO results (v1, v2) VALUES (%ld, %d)";

    for(int k=0; k<N; k++)
    {
      memset(ctx.stSQL, 0, SQL_BUFFER_LENGTH * sizeof(char));
      sprintf(ctx.stSQL, stSQLResultsInsert, v1, v2);
      ret = SPI_exec(ctx.stSQL, 0);
      proc_0 = SPI_processed;
      if(ret != SPI_OK_INSERT || proc_0 <= 0)
      {
        elog(ERROR, "spi_match: SPI_execute (8_H) returned %d", ret);
        my_spi_free_context(&ctx);
        PG_RETURN_VOID();
      }
    }

    /* some code with aggregation of data from TEMP TABLE results */

    memset(ctx.stSQL, 0, SQL_BUFFER_LENGTH * sizeof(char));
    sprintf(ctx.stSQL, "SELECT v1, v2 FROM results");
    ret = SPI_execute(ctx.stSQL, false, 0);
    proc = SPI_processed;

    ereport(NOTICE, (errmsg("P5: [%s]-(%d)", (const char*)__FUNCTION__, proc)));

    if(ret != SPI_OK_SELECT || proc <= 0)
    {
      funcctx->max_calls = 0;
      funcctx->user_fctx = NULL;
      if(proc <= 0) ereport(NOTICE, (errmsg("SPI_execute (10) returned %d", ret)));
    }
    else if(proc)
    {
      spi_tuptable = SPI_tuptable;

      funcctx->max_calls = proc;
      funcctx->user_fctx = spi_tuptable;
    }

    my_spi_free_context(&ctx);

    tupleDesc = BlessTupleDesc(tupleDesc);
    funcctx->tuple_desc = tupleDesc;
    MemoryContextSwitchTo(oldcontext);

  }

  funcctx = SRF_PERCALL_SETUP();

  call_cntr = funcctx->call_cntr;
  max_calls = funcctx->max_calls;

  if(call_cntr < max_calls)
  {
    SPITupleTable* table = (SPITupleTable*)funcctx->user_fctx;
    Datum       results; /* Results tuple */
    Datum       column[2];
    bool        isColumnNull[2];
    HeapTuple   tuple;
    int m;

    if(table)
    {
      for(m=0; m<2; m++)
      {
        column[m] = SPI_getbinval(table->vals[call_cntr], table->tupdesc, m+1, &isColumnNull[m]);
      }

      tuple = heap_form_tuple(funcctx->tuple_desc, column, isColumnNull);
      results = HeapTupleGetDatum(tuple);
      SRF_RETURN_NEXT(funcctx, results);
    }
  }
  else
  {
    int ret;
    SPITupleTable* table = (SPITupleTable*)funcctx->user_fctx;
    if(table)
    {
      SPI_freetuptable(table);
    }

    ereport(NOTICE, (errmsg("P6: [%s]-(%d)", (const char*)__FUNCTION__, max_calls)));

    ret = SPI_exec("DROP TABLE results", 0);
    if(ret != SPI_OK_UTILITY)
    {
      elog(ERROR, "spi_match: SPI_exec (20) returned %d", ret);
    }

    SPI_finish();
    SRF_RETURN_DONE(funcctx);
  }

  PG_RETURN_VOID();
}

--
Best regards,

Andrey Sychev

[hidden email]