Sqlite3 adding custom function

Question

I'm trying to add a custom rank function written in C for SQLite3. The code compiles, but I can't seem to load it in sqlite3. When I do .load './librank.so' in SQLite3, I see this error message:

./librank.so.so: cannot open shared object file: No such file or directory

The code (from http://www.sqlite.org/fts3.html#appendix_a)

Rank.c

#if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_RANK)
#include <stdio.h>
#ifndef SQLITE_CORE
  #include "sqlite3ext.h"
  SQLITE_EXTENSION_INIT1
#else
  #include "sqlite3.h"
#endif


static void rankfunc(sqlite3_context *pCtx, int nVal, sqlite3_value **apVal){
  int *aMatchinfo;                /* Return value of matchinfo() */
  int nCol;                       /* Number of columns in the table */
  int nPhrase;                    /* Number of phrases in the query */
  int iPhrase;                    /* Current phrase */
  double score = 0.0;             /* Value to return */

  assert( sizeof(int)==4 );

  /* Check that the number of arguments passed to this function is correct.
  ** If not, jump to wrong_number_args. Set aMatchinfo to point to the array
  ** of unsigned integer values returned by FTS function matchinfo. Set
  ** nPhrase to contain the number of reportable phrases in the users full-text
  ** query, and nCol to the number of columns in the table.
  */
  if( nVal<1 ) goto wrong_number_args;
  aMatchinfo = (unsigned int *)sqlite3_value_blob(apVal[0]);
  nPhrase = aMatchinfo[0];
  nCol = aMatchinfo[1];
  if( nVal!=(1+nCol) ) goto wrong_number_args;

  /* Iterate through each phrase in the users query. */
  for(iPhrase=0; iPhrase<nPhrase; iPhrase++){
    int iCol;                     /* Current column */

    /* Now iterate through each column in the users query. For each column,
    ** increment the relevancy score by:
    **
    **   (<hit count> / <global hit count>) * <column weight>
    **
    ** aPhraseinfo[] points to the start of the data for phrase iPhrase. So
    ** the hit count and global hit counts for each column are found in 
    ** aPhraseinfo[iCol*3] and aPhraseinfo[iCol*3+1], respectively.
    */
    int *aPhraseinfo = &aMatchinfo[2 + iPhrase*nCol*3];
    for(iCol=0; iCol<nCol; iCol++){
      int nHitCount = aPhraseinfo[3*iCol];
      int nGlobalHitCount = aPhraseinfo[3*iCol+1];
      double weight = sqlite3_value_double(apVal[iCol+1]);
      if( nHitCount>0 ){
        score += ((double)nHitCount / (double)nGlobalHitCount) * weight;
      }
    }
  }

  sqlite3_result_double(pCtx, score);
  return;

  /* Jump here if the wrong number of arguments are passed to this function */
wrong_number_args:
  sqlite3_result_error(pCtx, "wrong number of arguments to function rank()", -1);
}

int sqlite3rankInit(sqlite3 *db){
  sqlite3_create_function(db, "rank", -1, SQLITE_UTF8, 0, &rankfunc, 0, 0);
  return 0;
}

#if !SQLITE_CORE
int sqlite3_extension_init(
  sqlite3 *db, 
  char **pzErrMsg,
  const sqlite3_api_routines *pApi
){
  SQLITE_EXTENSION_INIT2(pApi)
  return sqlite3rankInit(db);
}
#endif

#endif


Compiled with: gcc -shared -fPIC -lm rank.c -o librank.so

Can someone help me see what I did incorrectly?

implmentor · Accepted Answer · 2015-08-12 07:08:44Z

1

Try to include the assert header

diff --git a/rank_orig.c b/rank.c
index 5d51b4d..4940e1b 100644
--- a/rank_orig.c
+++ b/rank.c
@@ -1,5 +1,6 @@
 #if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_RANK)
 #include <stdio.h>
+#include <assert.h>
 #ifndef SQLITE_CORE
   #include "sqlite3ext.h"

Compile:

$ gcc -shared -fPIC -lm rank.c -o librank.so

Load

$ sqlite3 
SQLite version 3.8.10.1 2015-05-09 12:14:55
sqlite> .load ./librank.so 
sqlite>

answered Aug 12, 2015 at 7:08

implmentor

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Comments

CL. · Accepted Answer · 2015-08-12 07:54:27Z

0

The error message shows that SQLite already appends ".so" to the file name. So you must specify the bare library name:

> .load './librank'

answered Aug 12, 2015 at 7:54

CL.

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