SQLite

end_diff_one_table:
  strFree(&sql);
  sqlite3_free(zId);
  namelistFree(az);
  namelistFree(az2);
  return;
}

/*
** Generate a CHANGESET for all differences from main.zTab to aux.zTab.
*/
static void changeset_one_table(const char *zTab, FILE *out){
  sqlite3_stmt *pStmt;          /* SQL statment */
  char *zId = safeId(zTab);     /* Escaped name of the table */
  char **azCol = 0;             /* List of escaped column names */
  int nCol = 0;                 /* Number of columns */
  int *aiFlg = 0;               /* 0 if column is not part of PK */
  int *aiPk = 0;                /* Column numbers for each PK column */
  int nPk = 0;                  /* Number of PRIMARY KEY columns */
  Str sql;                      /* SQL for the diff query */
  int i;                        /* Loop counter */
  const char *zSep;             /* List separator */

  pStmt = db_prepare(
      "SELECT A.sql=B.sql FROM main.sqlite_master A, aux.sqlite_master B"
      " WHERE A.name=%Q AND B.name=%Q", zTab, zTab
  );
  if( SQLITE_ROW==sqlite3_step(pStmt) ){
    if( sqlite3_column_int(pStmt,0)==0 ){
      runtimeError("schema changes for table %s", safeId(zTab));
    }
  }else{
    runtimeError("table %s missing from one or both databases", safeId(zTab));
  }
  sqlite3_finalize(pStmt);
  pStmt = db_prepare("PRAGMA main.table_info=%Q", zTab);
  while( SQLITE_ROW==sqlite3_step(pStmt) ){
    nCol++;
    azCol = sqlite3_realloc(azCol, sizeof(char*)*nCol);
    if( azCol==0 ) runtimeError("out of memory");
    aiFlg = sqlite3_realloc(aiFlg, sizeof(int)*nCol);
    if( aiFlg==0 ) runtimeError("out of memory");
    azCol[nCol-1] = safeId((const char*)sqlite3_column_text(pStmt,1));
    aiFlg[nCol-1] = i = sqlite3_column_int(pStmt,5);
    if( i>0 ){
      if( i>nPk ){
        nPk = i;
        aiPk = sqlite3_realloc(aiPk, sizeof(int)*nPk);
        if( aiPk==0 ) runtimeError("out of memory");
      }
      aiPk[i-1] = nCol-1;
    }
  }
  sqlite3_finalize(pStmt);
  if( nPk==0 ) goto end_changeset_one_table; 
  strInit(&sql);
  if( nCol>nPk ){
    strPrintf(&sql, "SELECT 1");  /* Changes to non-PK columns */
    for(i=0; i<nCol; i++) strPrintf(&sql, ", A.%s", azCol[i]);
    for(i=0; i<nCol; i++) strPrintf(&sql, ", B.%s", azCol[i]);
    strPrintf(&sql,"\n  FROM main.%s A, aux.%s B\n", zId, zId);
    zSep = " WHERE";
    for(i=0; i<nPk; i++){
      strPrintf(&sql, "%s A.%s=B.%s", zSep, azCol[aiPk[i]], azCol[aiPk[i]]);
      zSep = " AND";
    }
    zSep = "\n   AND (";
    for(i=0; i<nCol; i++){
      if( aiFlg[i] ) continue;
      strPrintf(&sql, "%sA.%s IS NOT B.%s", zSep, azCol[i], azCol[i]);
      zSep = " OR\n        ";
    }
    strPrintf(&sql,")\n UNION ALL\n");
  }
  strPrintf(&sql, "SELECT 2");   /* Deleted rows */
  for(i=0; i<nCol; i++) strPrintf(&sql, ", A.%s", azCol[i]);
  for(i=0; i<nCol; i++) strPrintf(&sql, ", 0");
  strPrintf(&sql, "  FROM main.%s A\n", zId);
  strPrintf(&sql, " WHERE NOT EXISTS(SELECT 1 FROM aux.%s B\n", zId);
  zSep =          "                   WHERE";
  for(i=0; i<nPk; i++){
    strPrintf(&sql, "%s A.%s=B.%s", zSep, azCol[aiPk[i]], azCol[aiPk[i]]);
    zSep = " AND";
  }
  strPrintf(&sql, ")\n UNION ALL\n");
  strPrintf(&sql, "SELECT 3");   /* Inserted rows */
  for(i=0; i<nCol; i++) strPrintf(&sql, ", 0");
  for(i=0; i<nCol; i++) strPrintf(&sql, ", B.%s", azCol[i]);
  strPrintf(&sql, "  FROM aux.%s B\n", zId);
  strPrintf(&sql, " WHERE NOT EXISTS(SELECT 1 FROM main.%s A\n", zId);
  zSep =          "                   WHERE";
  for(i=0; i<nPk; i++){
    strPrintf(&sql, "%s A.%s=B.%s", zSep, azCol[aiPk[i]], azCol[aiPk[i]]);
    zSep = " AND";
  }
  strPrintf(&sql, ")\n");
  strPrintf(&sql, " ORDER BY");
  zSep = " ";
  for(i=0; i<nPk; i++){
    strPrintf(&sql, "%s %d", zSep, aiPk[i]+1);
    zSep = ",";
  }
  strPrintf(&sql, ";\n");

printf("for table %s:\n%s\n", zId, sql.z);
strFree(&sql);
  
  
end_changeset_one_table:
  while( nCol>0 ) sqlite3_free(azCol[--nCol]);
  sqlite3_free(azCol);
  sqlite3_free(aiPk);
  sqlite3_free(zId);
}

/*
** Print sketchy documentation for this utility program
*/
static void showHelp(void){
  printf("Usage: %s [options] DB1 DB2\n", g.zArgv0);
  printf(
"Output SQL text that would transform DB1 into DB2.\n"
"Options:\n"
"  --changeset FILE      Write a CHANGESET into FILE\n"
"  --primarykey          Use schema-defined PRIMARY KEYs\n"
"  --schema              Show only differences in the schema\n"
"  --table TAB           Show only differences in table TAB\n"
  );
}

int main(int argc, char **argv){
  const char *zDb1 = 0;
  const char *zDb2 = 0;
  int i;
  int rc;
  char *zErrMsg = 0;
  char *zSql;
  sqlite3_stmt *pStmt;
  char *zTab = 0;
  FILE *out = 0;

  g.zArgv0 = argv[0];
  for(i=1; i<argc; i++){
    const char *z = argv[i];
    if( z[0]=='-' ){
      z++;
      if( z[0]=='-' ) z++;
      if( strcmp(z,"changeset")==0 ){
        out = fopen(argv[++i], "wb");
        if( out==0 ) cmdlineError("cannot open: %s", argv[i]);
      }else
      if( strcmp(z,"debug")==0 ){
        g.fDebug = strtol(argv[++i], 0, 0);
      }else
      if( strcmp(z,"help")==0 ){
        showHelp();
        return 0;
      }else

  }
  rc = sqlite3_exec(g.db, "SELECT * FROM aux.sqlite_master", 0, 0, &zErrMsg);
  if( rc || zErrMsg ){
    cmdlineError("\"%s\" does not appear to be a valid SQLite database", zDb2);
  }

  if( zTab ){
    if( out ){
      changeset_one_table(zTab, out);
    }else{
      diff_one_table(zTab);
    }
  }else{
    /* Handle tables one by one */
    pStmt = db_prepare(
      "SELECT name FROM main.sqlite_master\n"
      " WHERE type='table' AND sql NOT LIKE 'CREATE VIRTUAL%%'\n"
      " UNION\n"
      "SELECT name FROM aux.sqlite_master\n"
      " WHERE type='table' AND sql NOT LIKE 'CREATE VIRTUAL%%'\n"
      " ORDER BY name"
    );
    while( SQLITE_ROW==sqlite3_step(pStmt) ){
      const char *zTab = (const char*)sqlite3_column_text(pStmt,0);
      if( out ){
        changeset_one_table(zTab, out);
      }else{
        diff_one_table(zTab);
      }
    }
    sqlite3_finalize(pStmt);
  }

  /* TBD: Handle trigger differences */
  /* TBD: Handle view differences */
  sqlite3_close(g.db);
  return 0;
}