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Overview
Comment:Remove genfkey.c. Change genfkey.README to talk about the new shell dot-command, not the old standalone genfkey program. (CVS 6326)
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Timelines: family | ancestors | descendants | both | trunk
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SHA1:36d699660bc328e65170d72be715338e82dbbb50
User & Date: danielk1977 2009-02-25 15:43:57
Context
2009-02-25
19:07
Move the new genfkey shell command out from within #ifdef _WIN32_ (CVS 6327) check-in: 48ee0e47 user: drh tags: trunk
15:43
Remove genfkey.c. Change genfkey.README to talk about the new shell dot-command, not the old standalone genfkey program. (CVS 6326) check-in: 36d69966 user: danielk1977 tags: trunk
15:22
Add the 'genfkey' functionality to the sqlite3 shell. Accessed using a new dot-command - ".genfkey". (CVS 6325) check-in: 0a59fb28 user: danielk1977 tags: trunk
Changes
Hide Diffs Unified Diffs Ignore Whitespace Patch

Changes to src/shell.c.

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**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains code to implement the "sqlite" command line
** utility for accessing SQLite databases.
**
** $Id: shell.c,v 1.202 2009/02/25 15:22:03 danielk1977 Exp $
*/
#if defined(_WIN32) || defined(WIN32)
/* This needs to come before any includes for MSVC compiler */
#define _CRT_SECURE_NO_WARNINGS
#endif

#include <stdlib.h>
................................................................................
  ".exit                  Exit this program\n"
  ".explain ON|OFF        Turn output mode suitable for EXPLAIN on or off.\n"
#if !defined(SQLITE_OMIT_VIRTUALTABLE) && !defined(SQLITE_OMIT_SUBQUERY)
  ".genfkey ?OPTIONS?     Options are:\n"
  "                         --no-drop: Do not drop old fkey triggers.\n"
  "                         --ignore-errors: Ignore tables with fkey errors\n"
  "                         --exec: Execute generated SQL immediately\n"

  "                         --help: Print help message for .genfkey\n"
#endif
  ".header(s) ON|OFF      Turn display of headers on or off\n"
  ".help                  Show this message\n"
  ".import FILE TABLE     Import data from FILE into TABLE\n"
  ".indices TABLE         Show names of all indices on TABLE\n"
#ifdef SQLITE_ENABLE_IOTRACE
  ".iotrace FILE          Enable I/O diagnostic logging to FILE\n"







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**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains code to implement the "sqlite" command line
** utility for accessing SQLite databases.
**
** $Id: shell.c,v 1.203 2009/02/25 15:43:57 danielk1977 Exp $
*/
#if defined(_WIN32) || defined(WIN32)
/* This needs to come before any includes for MSVC compiler */
#define _CRT_SECURE_NO_WARNINGS
#endif

#include <stdlib.h>
................................................................................
  ".exit                  Exit this program\n"
  ".explain ON|OFF        Turn output mode suitable for EXPLAIN on or off.\n"
#if !defined(SQLITE_OMIT_VIRTUALTABLE) && !defined(SQLITE_OMIT_SUBQUERY)
  ".genfkey ?OPTIONS?     Options are:\n"
  "                         --no-drop: Do not drop old fkey triggers.\n"
  "                         --ignore-errors: Ignore tables with fkey errors\n"
  "                         --exec: Execute generated SQL immediately\n"
  "                       See file tool/genfkey.README in the source \n"
  "                       distribution for further information.\n"
#endif
  ".header(s) ON|OFF      Turn display of headers on or off\n"
  ".help                  Show this message\n"
  ".import FILE TABLE     Import data from FILE into TABLE\n"
  ".indices TABLE         Show names of all indices on TABLE\n"
#ifdef SQLITE_ENABLE_IOTRACE
  ".iotrace FILE          Enable I/O diagnostic logging to FILE\n"

Changes to tool/genfkey.README.

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OVERVIEW

  The SQLite library is capable of parsing SQL foreign key constraints 
  supplied as part of CREATE TABLE statements, but it does not actually 
  implement them. However, most of the features of foreign keys may be
  implemented using SQL triggers, which SQLite does support. This program 

  extracts foreign key definitions from an existing SQLite database and
  outputs the set of CREATE TRIGGER statements required to implement
  the foreign key constraints.

CAPABILITIES

  An SQL foreign key is a constraint that requires that each row in
  the "child" table corresponds to a row in the "parent" table. For
  example, the following schema:
................................................................................
      SET NULL foreign key are the same table, the generated triggers will
      malfunction. This is also true if the recursive foreign key constraint
      is indirect (for example if table A references table B which references
      table A with a CASCADE or SET NULL foreign key constraint).

      Recursive CASCADE or SET NULL foreign key relationships are *not*
      detected as errors when the program is run. Buyer beware.
      
COMPILATION

  The source code for this program consists of a single C file - genfkey.c.
  The only dependency is sqlite itself. Using gcc and the sqlite amalgamation
  source code, it may be compiled using the following command:

    gcc genfkey.c sqlite3.c -o genfkey

  Or, to use an installed version of sqlite (the kind linux distributions
  install as part of the sqlite3-dev package):

    gcc genfkey.c -lsqlite3 -o genfkey

  If compiled/linked against an SQLite version earlier than 3.6.4, then
  all foreign key constraints are assumed to be "ON UPDATE RESTRICT" and
  "ON DELETE RESTRICT". If linked against 3.6.4 or newer, "CASCADE" and
  "SET NULL" are supported as well as "RESTRICT". All 3.x versions of SQLite
  may use the created triggers definitions.

USAGE



    genfkey ?--no-drop? ?--ignore-errors? <sqlite database>

  When this program is run, it first checks the schema of the supplied SQLite
  database for foreign key related errors or inconsistencies. For example,
  a foreign key that refers to a parent table that does not exist, or
  a foreign key that refers to columns in a parent table that are not
  guaranteed to be unique. If such errors are found, a message for each
  one is printed to stderr.


  If errors are found and the --ignore-errors option was not passed, the
  program exits. Otherwise, a series of SQL trigger definitions (CREATE 
  TRIGGER statements) that implement the foreign key constraints found
  in the database schema are written to stdout. If any errors were 
  found in the schema, no triggers for the problematic constraints are
  output. The output CREATE TRIGGER statements should be run against the
  database to enable enforcement of the foreign key constraints. For
  example, for a database named "test.db" in the current working directory:

    $ genfkey ./test.db | sqlite3 ./test.db

  All triggers generated by this program have names that match the pattern
  "genfkey*". Unless the --no-drop option is specified, then the program
  also outputs a "DROP TRIGGER" statement for each trigger that exists
  in the database with a name that matches this pattern. This allows the
  program to be used to upgrade a database schema for which foreign key
  triggers have already been installed (i.e. after new tables are created
  or existing tables dropped).
  






















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OVERVIEW

  The SQLite library is capable of parsing SQL foreign key constraints 
  supplied as part of CREATE TABLE statements, but it does not actually 
  implement them. However, most of the features of foreign keys may be
  implemented using SQL triggers, which SQLite does support. This text
  file describes a feature of the SQLite shell tool (sqlite3) that
  extracts foreign key definitions from an existing SQLite database and
  creates the set of CREATE TRIGGER statements required to implement
  the foreign key constraints.

CAPABILITIES

  An SQL foreign key is a constraint that requires that each row in
  the "child" table corresponds to a row in the "parent" table. For
  example, the following schema:
................................................................................
      SET NULL foreign key are the same table, the generated triggers will
      malfunction. This is also true if the recursive foreign key constraint
      is indirect (for example if table A references table B which references
      table A with a CASCADE or SET NULL foreign key constraint).

      Recursive CASCADE or SET NULL foreign key relationships are *not*
      detected as errors when the program is run. Buyer beware.




















USAGE

  The functionality is accessed through an sqlite3 shell tool "dot-command":

    .genfkey ?--no-drop? ?--ignore-errors? ?--exec?

  When this command is run, it first checks the schema of the open SQLite
  database for foreign key related errors or inconsistencies. For example,
  a foreign key that refers to a parent table that does not exist, or
  a foreign key that refers to columns in a parent table that are not
  guaranteed to be unique. If such errors are found and the --ignore-errors
  option was not present, a message for each one is printed to stderr and
  no further processing takes place.

  If errors are found and the --ignore-errors option is passed, then

  no error messages are printed. No "CREATE TRIGGER" statements are generated
  for foriegn-key definitions that contained errors, they are silently
  ignored by subsequent processing.






  All triggers generated by this command have names that match the pattern
  "genfkey*". Unless the --no-drop option is specified, then the program
  also generates a "DROP TRIGGER" statement for each trigger that exists
  in the database with a name that matches this pattern. This allows the
  program to be used to upgrade a database schema for which foreign key
  triggers have already been installed (i.e. after new tables are created
  or existing tables dropped).

  Finally, a series of SQL trigger definitions (CREATE TRIGGER statements) 
  that implement the foreign key constraints found in the database schema are
  generated.

  If the --exec option was passed, then all generated SQL is immediately
  executed on the database. Otherwise, the generated SQL strings are output
  in the same way as the results of SELECT queries are. Normally, this means
  they will be printed to stdout, but this can be configured using other
  dot-commands (i.e. ".output").

  The simplest way to activate the foriegn key definitions in a database
  is simply to open it using the shell tool and enter the command 
  ".genfkey --exec":

    sqlite> .genfkey --exec

Deleted tool/genfkey.c.

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/*
** 2008 October 10
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains C code for 'genfkey', a program to generate trigger
** definitions that emulate foreign keys. See genfkey.README for details.
**
** $Id: genfkey.c,v 1.2 2008/10/13 10:56:48 danielk1977 Exp $
*/

#include "sqlite3.h"
#include <stdio.h>
#include <assert.h>
#include <stdlib.h>
#include <string.h>

/**************************************************************************
***************************************************************************
** Start of virtual table implementations.
**************************************************************************/

/* The code in this file defines a sqlite3 virtual-table module that
** provides a read-only view of the current database schema. There is one
** row in the schema table for each column in the database schema.
*/
#define SCHEMA \
"CREATE TABLE x("                                                            \
  "database,"          /* Name of database (i.e. main, temp etc.) */         \
  "tablename,"         /* Name of table */                                   \
  "cid,"               /* Column number (from left-to-right, 0 upward) */    \
  "name,"              /* Column name */                                     \
  "type,"              /* Specified type (i.e. VARCHAR(32)) */               \
  "not_null,"          /* Boolean. True if NOT NULL was specified */         \
  "dflt_value,"        /* Default value for this column */                   \
  "pk"                 /* True if this column is part of the primary key */  \
")"

#define SCHEMA2 \
"CREATE TABLE x("                                                            \
  "database,"          /* Name of database (i.e. main, temp etc.) */         \
  "from_tbl,"          /* Name of table */                                   \
  "fkid,"                                                                    \
  "seq,"                                                                     \
  "to_tbl,"                                                                  \
  "from_col,"                                                                \
  "to_col,"                                                                  \
  "on_update,"                                                               \
  "on_delete,"                                                               \
  "match"                                                                    \
")"

#define SCHEMA3 \
"CREATE TABLE x("                                                            \
  "database,"          /* Name of database (i.e. main, temp etc.) */         \
  "tablename,"         /* Name of table */                                   \
  "seq,"                                                                     \
  "name,"                                                                    \
  "isunique"                                                                 \
")"

#define SCHEMA4 \
"CREATE TABLE x("                                                            \
  "database,"          /* Name of database (i.e. main, temp etc.) */         \
  "indexname,"         /* Name of table */                                   \
  "seqno,"                                                                   \
  "cid,"                                                                     \
  "name"                                                                     \
")"

typedef struct SchemaTable SchemaTable;
struct SchemaTable {
  const char *zName;
  const char *zObject;
  const char *zPragma;
  const char *zSchema;
} aSchemaTable[] = {
  { "table_info",       "table", "PRAGMA %Q.table_info(%Q)",       SCHEMA },
  { "foreign_key_list", "table", "PRAGMA %Q.foreign_key_list(%Q)", SCHEMA2 },
  { "index_list",       "table", "PRAGMA %Q.index_list(%Q)",       SCHEMA3 },
  { "index_info",       "index", "PRAGMA %Q.index_info(%Q)",       SCHEMA4 },
  { 0, 0, 0, 0 }
};

typedef struct schema_vtab schema_vtab;
typedef struct schema_cursor schema_cursor;

/* A schema table object */
struct schema_vtab {
  sqlite3_vtab base;
  sqlite3 *db;
  SchemaTable *pType;
};

/* A schema table cursor object */
struct schema_cursor {
  sqlite3_vtab_cursor base;
  sqlite3_stmt *pDbList;
  sqlite3_stmt *pTableList;
  sqlite3_stmt *pColumnList;
  int rowid;
};

/*
** Table destructor for the schema module.
*/
static int schemaDestroy(sqlite3_vtab *pVtab){
  sqlite3_free(pVtab);
  return 0;
}

/*
** Table constructor for the schema module.
*/
static int schemaCreate(
  sqlite3 *db,
  void *pAux,
  int argc, const char *const*argv,
  sqlite3_vtab **ppVtab,
  char **pzErr
){
  int rc = SQLITE_NOMEM;
  schema_vtab *pVtab;
  SchemaTable *pType = &aSchemaTable[0];

  if( argc>3 ){
    int i;
    pType = 0;
    for(i=0; aSchemaTable[i].zName; i++){ 
      if( 0==strcmp(argv[3], aSchemaTable[i].zName) ){
        pType = &aSchemaTable[i];
      }
    }
    if( !pType ){
      return SQLITE_ERROR;
    }
  }

  pVtab = sqlite3_malloc(sizeof(schema_vtab));
  if( pVtab ){
    memset(pVtab, 0, sizeof(schema_vtab));
    pVtab->db = db;
    pVtab->pType = pType;
    rc = sqlite3_declare_vtab(db, pType->zSchema);
  }
  *ppVtab = (sqlite3_vtab *)pVtab;
  return rc;
}

/*
** Open a new cursor on the schema table.
*/
static int schemaOpen(sqlite3_vtab *pVTab, sqlite3_vtab_cursor **ppCursor){
  int rc = SQLITE_NOMEM;
  schema_cursor *pCur;
  pCur = sqlite3_malloc(sizeof(schema_cursor));
  if( pCur ){
    memset(pCur, 0, sizeof(schema_cursor));
    *ppCursor = (sqlite3_vtab_cursor *)pCur;
    rc = SQLITE_OK;
  }
  return rc;
}

/*
** Close a schema table cursor.
*/
static int schemaClose(sqlite3_vtab_cursor *cur){
  schema_cursor *pCur = (schema_cursor *)cur;
  sqlite3_finalize(pCur->pDbList);
  sqlite3_finalize(pCur->pTableList);
  sqlite3_finalize(pCur->pColumnList);
  sqlite3_free(pCur);
  return SQLITE_OK;
}

/*
** Retrieve a column of data.
*/
static int schemaColumn(sqlite3_vtab_cursor *cur, sqlite3_context *ctx, int i){
  schema_cursor *pCur = (schema_cursor *)cur;
  switch( i ){
    case 0:
      sqlite3_result_value(ctx, sqlite3_column_value(pCur->pDbList, 1));
      break;
    case 1:
      sqlite3_result_value(ctx, sqlite3_column_value(pCur->pTableList, 0));
      break;
    default:
      sqlite3_result_value(ctx, sqlite3_column_value(pCur->pColumnList, i-2));
      break;
  }
  return SQLITE_OK;
}

/*
** Retrieve the current rowid.
*/
static int schemaRowid(sqlite3_vtab_cursor *cur, sqlite_int64 *pRowid){
  schema_cursor *pCur = (schema_cursor *)cur;
  *pRowid = pCur->rowid;
  return SQLITE_OK;
}

static int finalize(sqlite3_stmt **ppStmt){
  int rc = sqlite3_finalize(*ppStmt);
  *ppStmt = 0;
  return rc;
}

static int schemaEof(sqlite3_vtab_cursor *cur){
  schema_cursor *pCur = (schema_cursor *)cur;
  return (pCur->pDbList ? 0 : 1);
}

/*
** Advance the cursor to the next row.
*/
static int schemaNext(sqlite3_vtab_cursor *cur){
  int rc = SQLITE_OK;
  schema_cursor *pCur = (schema_cursor *)cur;
  schema_vtab *pVtab = (schema_vtab *)(cur->pVtab);
  char *zSql = 0;

  while( !pCur->pColumnList || SQLITE_ROW!=sqlite3_step(pCur->pColumnList) ){
    if( SQLITE_OK!=(rc = finalize(&pCur->pColumnList)) ) goto next_exit;

    while( !pCur->pTableList || SQLITE_ROW!=sqlite3_step(pCur->pTableList) ){
      if( SQLITE_OK!=(rc = finalize(&pCur->pTableList)) ) goto next_exit;

      assert(pCur->pDbList);
      while( SQLITE_ROW!=sqlite3_step(pCur->pDbList) ){
        rc = finalize(&pCur->pDbList);
        goto next_exit;
      }

      /* Set zSql to the SQL to pull the list of tables from the 
      ** sqlite_master (or sqlite_temp_master) table of the database
      ** identfied by the row pointed to by the SQL statement pCur->pDbList
      ** (iterating through a "PRAGMA database_list;" statement).
      */
      if( sqlite3_column_int(pCur->pDbList, 0)==1 ){
        zSql = sqlite3_mprintf(
            "SELECT name FROM sqlite_temp_master WHERE type=%Q",
            pVtab->pType->zObject
        );
      }else{
        sqlite3_stmt *pDbList = pCur->pDbList;
        zSql = sqlite3_mprintf(
            "SELECT name FROM %Q.sqlite_master WHERE type=%Q",
             sqlite3_column_text(pDbList, 1), pVtab->pType->zObject
        );
      }
      if( !zSql ){
        rc = SQLITE_NOMEM;
        goto next_exit;
      }

      rc = sqlite3_prepare(pVtab->db, zSql, -1, &pCur->pTableList, 0);
      sqlite3_free(zSql);
      if( rc!=SQLITE_OK ) goto next_exit;
    }

    /* Set zSql to the SQL to the table_info pragma for the table currently
    ** identified by the rows pointed to by statements pCur->pDbList and
    ** pCur->pTableList.
    */
    zSql = sqlite3_mprintf(pVtab->pType->zPragma,
        sqlite3_column_text(pCur->pDbList, 1),
        sqlite3_column_text(pCur->pTableList, 0)
    );

    if( !zSql ){
      rc = SQLITE_NOMEM;
      goto next_exit;
    }
    rc = sqlite3_prepare(pVtab->db, zSql, -1, &pCur->pColumnList, 0);
    sqlite3_free(zSql);
    if( rc!=SQLITE_OK ) goto next_exit;
  }
  pCur->rowid++;

next_exit:
  /* TODO: Handle rc */
  return rc;
}

/*
** Reset a schema table cursor.
*/
static int schemaFilter(
  sqlite3_vtab_cursor *pVtabCursor, 
  int idxNum, const char *idxStr,
  int argc, sqlite3_value **argv
){
  int rc;
  schema_vtab *pVtab = (schema_vtab *)(pVtabCursor->pVtab);
  schema_cursor *pCur = (schema_cursor *)pVtabCursor;
  pCur->rowid = 0;
  finalize(&pCur->pTableList);
  finalize(&pCur->pColumnList);
  finalize(&pCur->pDbList);
  rc = sqlite3_prepare(pVtab->db,"SELECT 0, 'main'", -1, &pCur->pDbList, 0);
  return (rc==SQLITE_OK ? schemaNext(pVtabCursor) : rc);
}

/*
** Analyse the WHERE condition.
*/
static int schemaBestIndex(sqlite3_vtab *tab, sqlite3_index_info *pIdxInfo){
  return SQLITE_OK;
}

/*
** A virtual table module that merely echos method calls into TCL
** variables.
*/
static sqlite3_module schemaModule = {
  0,                           /* iVersion */
  schemaCreate,
  schemaCreate,
  schemaBestIndex,
  schemaDestroy,
  schemaDestroy,
  schemaOpen,                  /* xOpen - open a cursor */
  schemaClose,                 /* xClose - close a cursor */
  schemaFilter,                /* xFilter - configure scan constraints */
  schemaNext,                  /* xNext - advance a cursor */
  schemaEof,                   /* xEof */
  schemaColumn,                /* xColumn - read data */
  schemaRowid,                 /* xRowid - read data */
  0,                           /* xUpdate */
  0,                           /* xBegin */
  0,                           /* xSync */
  0,                           /* xCommit */
  0,                           /* xRollback */
  0,                           /* xFindMethod */
  0,                           /* xRename */
};

/*
** Extension load function.
*/
static int installSchemaModule(sqlite3 *db){
  sqlite3_create_module(db, "schema", &schemaModule, 0);
  return 0;
}

/**************************************************************************
***************************************************************************
** End of virtual table implementations.
** Start of SQL user function implementations.
*/

/*
**   sj(zValue, zJoin)
**
** The following block contains the implementation of an aggregate 
** function that returns a string. Each time the function is stepped, 
** it appends data to an internal buffer. When the aggregate is finalized,
** the contents of the buffer are returned.
**
** The first time the aggregate is stepped the buffer is set to a copy
** of the first argument. The second time and subsequent times it is
** stepped a copy of the second argument is appended to the buffer, then
** a copy of the first.
**
** Example:
**
**   INSERT INTO t1(a) VALUES('1');
**   INSERT INTO t1(a) VALUES('2');
**   INSERT INTO t1(a) VALUES('3');
**   SELECT sj(a, ', ') FROM t1;
**
**     =>  "1, 2, 3"
**
*/
struct StrBuffer {
  char *zBuf;
};
typedef struct StrBuffer StrBuffer;
static void joinFinalize(sqlite3_context *context){
  StrBuffer *p;
  p = (StrBuffer *)sqlite3_aggregate_context(context, sizeof(StrBuffer));
  sqlite3_result_text(context, p->zBuf, -1, SQLITE_TRANSIENT);
  sqlite3_free(p->zBuf);
}
static void joinStep(
  sqlite3_context *context,
  int argc,
  sqlite3_value **argv
){
  StrBuffer *p;
  p = (StrBuffer *)sqlite3_aggregate_context(context, sizeof(StrBuffer));
  if( p->zBuf==0 ){
    p->zBuf = sqlite3_mprintf("%s", sqlite3_value_text(argv[0]));
  }else{
    char *zTmp = p->zBuf;
    p->zBuf = sqlite3_mprintf("%s%s%s", 
        zTmp, sqlite3_value_text(argv[1]), sqlite3_value_text(argv[0])
    );
    sqlite3_free(zTmp);
  }
}

/*
**   dq(zString)
**
** This scalar function accepts a single argument and interprets it as
** a text value. The return value is the argument enclosed in double
** quotes. If any double quote characters are present in the argument, 
** these are escaped.
**
**   dq('the raven "Nevermore."') == '"the raven ""Nevermore."""'
*/
static void doublequote(
  sqlite3_context *context, 
  int argc, 
  sqlite3_value **argv
){
  int ii;
  char *zOut;
  char *zCsr;
  const char *zIn = (const char *)sqlite3_value_text(argv[0]);
  int nIn = sqlite3_value_bytes(argv[0]);

  zOut = sqlite3_malloc(nIn*2+3);
  zCsr = zOut;
  *zCsr++ = '"';
  for(ii=0; ii<nIn; ii++){
    *zCsr++ = zIn[ii];
    if( zIn[ii]=='"' ){
      *zCsr++ = '"';
    }
  }
  *zCsr++ = '"';
  *zCsr++ = '\0';

  sqlite3_result_text(context, zOut, -1, SQLITE_TRANSIENT);
  sqlite3_free(zOut);
}

/*
**   multireplace(zString, zSearch1, zReplace1, ...)
*/
static void multireplace(
  sqlite3_context *context, 
  int argc, 
  sqlite3_value **argv
){
  int i = 0;
  char *zOut = 0;
  int nOut = 0;
  int nMalloc = 0;
  const char *zIn = (const char *)sqlite3_value_text(argv[0]);
  int nIn = sqlite3_value_bytes(argv[0]);

  while( i<nIn ){
    const char *zCopy = &zIn[i];
    int nCopy = 1;
    int nReplace = 1;
    int j;
    for(j=1; j<(argc-1); j+=2){
      const char *z = (const char *)sqlite3_value_text(argv[j]);
      int n = sqlite3_value_bytes(argv[j]);
      if( n<=(nIn-i) && 0==strncmp(z, zCopy, n) ){
        zCopy = (const char *)sqlite3_value_text(argv[j+1]);
        nCopy = sqlite3_value_bytes(argv[j+1]);
        nReplace = n;
        break;
      }
    }
    if( (nOut+nCopy)>nMalloc ){
      nMalloc += (nMalloc + 16);
      zOut = (char *)sqlite3_realloc(zOut, nMalloc);
    }
    memcpy(&zOut[nOut], zCopy, nCopy);
    i += nReplace;
    nOut += nCopy;
  }

  sqlite3_result_text(context, zOut, nOut, SQLITE_TRANSIENT);
  sqlite3_free(zOut);
}

/**************************************************************************
***************************************************************************
** End of SQL user function implementations.
** Start of application implementation.
*/

typedef struct Options Options;
struct Options {
  char *zDb;
  int ignoreErrors;
  int noDrop;
};

/*
** Print out a usage message for the command line and exit. This is
** called from processCmdLine() if the program is invoked incorrectly.
*/
static int usage(char *zProgram){
  fprintf(stderr, 
      "Usage: %s ?--ignore-errors? ?--no-drop? <database file>\n", zProgram
  );
  exit(-1);
}

static void processCmdLine(int nArg, char **azArg, Options *p){
  int i;
  assert( nArg>0 );
  if( nArg<2 ){
    usage(azArg[0]);
  }
  for(i=1; i<(nArg-1); i++){
    char *z = azArg[i];
    if( 0==strcmp(z, "--ignore-errors") ){
      p->ignoreErrors = 1;
    }
    else if( 0==strcmp(z, "--no-drop") ){
      p->noDrop = 1;
    }
    else usage(azArg[0]);
  }
  p->zDb = azArg[nArg-1];
}

/*
** A callback for sqlite3_exec() that prints its first argument to
** stdout followed by a newline.
*/
static int printString(void *p, int nArg, char **azArg, char **azCol){
  printf("%s\n", azArg[0]);
  return SQLITE_OK;
}

int detectSchemaProblem(
  sqlite3 *db,                   /* Database connection */
  const char *zMessage,          /* English language error message */
  const char *zSql,              /* SQL statement to run */
  int *pHasErrors                /* Set *pHasErrors==1 if errors found */
){
  sqlite3_stmt *pStmt;
  int rc;
  rc = sqlite3_prepare(db, zSql, -1, &pStmt, 0);
  if( rc!=SQLITE_OK ){
    return rc;
  }
  while( SQLITE_ROW==sqlite3_step(pStmt) ){
    char *zDel;
    int iFk = sqlite3_column_int(pStmt, 0);
    const char *zTab = (const char *)sqlite3_column_text(pStmt, 1);
    fprintf(stderr, "Error in table %s: %s\n", zTab, zMessage);
    zDel = sqlite3_mprintf(
        "DELETE FROM temp.fkey WHERE from_tbl = %Q AND fkid = %d"
        , zTab, iFk
    );
    sqlite3_exec(db, zDel, 0, 0, 0);
    sqlite3_free(zDel);
    *pHasErrors = 1;
  }
  sqlite3_finalize(pStmt);
  return SQLITE_OK;
}

/*
** Create and populate temporary table "fkey".
*/
static int populateTempTable(sqlite3 *db, char **pzErr, int *pHasErrors){
  int rc;

  rc = sqlite3_exec(db, 
      "CREATE VIRTUAL TABLE temp.v_fkey USING schema(foreign_key_list);"
      "CREATE VIRTUAL TABLE temp.v_col USING schema(table_info);"
      "CREATE VIRTUAL TABLE temp.v_idxlist USING schema(index_list);"
      "CREATE VIRTUAL TABLE temp.v_idxinfo USING schema(index_info);"

      "CREATE TABLE temp.fkey AS "
        "SELECT from_tbl, to_tbl, fkid, from_col, to_col, on_update, on_delete "
        "FROM temp.v_fkey WHERE database = 'main';"

      , 0, 0, pzErr
  );
  if( rc!=SQLITE_OK ) return rc;

  rc = detectSchemaProblem(db, "foreign key columns do not exist",
    "SELECT fkid, from_tbl "
    "FROM temp.fkey "
    "WHERE to_col IS NOT NULL AND NOT EXISTS (SELECT 1 "
        "FROM temp.v_col WHERE tablename=to_tbl AND name==to_col"
    ")", pHasErrors
  );
  if( rc!=SQLITE_OK ) return rc;

  /* At this point the temp.fkey table is mostly populated. If any foreign
  ** keys were specified so that they implicitly refer to they primary
  ** key of the parent table, the "to_col" values of the temp.fkey rows
  ** are still set to NULL.
  **
  ** This is easily fixed for single column primary keys, but not for
  ** composites. With a composite primary key, there is no way to reliably
  ** query sqlite for the order in which the columns that make up the
  ** composite key were declared i.e. there is no way to tell if the
  ** schema actually contains "PRIMARY KEY(a, b)" or "PRIMARY KEY(b, a)".
  ** Therefore, this case is not handled. The following function call
  ** detects instances of this case.
  */
  rc = detectSchemaProblem(db, "implicit mapping to composite primary key",
    "SELECT fkid, from_tbl "
    "FROM temp.fkey "
    "WHERE to_col IS NULL "
    "GROUP BY fkid, from_tbl HAVING count(*) > 1", pHasErrors
  );
  if( rc!=SQLITE_OK ) return rc;

  /* Detect attempts to implicitly map to the primary key of a table 
  ** that has no primary key column.
  */
  rc = detectSchemaProblem(db, "implicit mapping to non-existant primary key",
    "SELECT fkid, from_tbl "
    "FROM temp.fkey "
    "WHERE to_col IS NULL AND NOT EXISTS "
      "(SELECT 1 FROM temp.v_col WHERE pk AND tablename = temp.fkey.to_tbl)"
    , pHasErrors
  );
  if( rc!=SQLITE_OK ) return rc;

  /* Fix all the implicit primary key mappings in the temp.fkey table. */
  rc = sqlite3_exec(db, 
    "UPDATE temp.fkey SET to_col = "
      "(SELECT name FROM temp.v_col WHERE pk AND tablename=temp.fkey.to_tbl)"
    " WHERE to_col IS NULL;"
    , 0, 0, pzErr
  );
  if( rc!=SQLITE_OK ) return rc;

  /* Now check that all all parent keys are either primary keys or 
  ** subject to a unique constraint.
  */
  rc = sqlite3_exec(db, 
    "CREATE TABLE temp.idx2 AS SELECT "
      "il.tablename AS tablename,"
      "ii.indexname AS indexname,"
      "ii.name AS col "
      "FROM temp.v_idxlist AS il, temp.v_idxinfo AS ii "
      "WHERE il.isunique AND il.database='main' AND ii.indexname = il.name;"
    "INSERT INTO temp.idx2 "
      "SELECT tablename, 'pk', name FROM temp.v_col WHERE pk;"

    "CREATE TABLE temp.idx AS SELECT "
      "tablename, indexname, sj(dq(col),',') AS cols "
      "FROM (SELECT * FROM temp.idx2 ORDER BY col) " 
      "GROUP BY tablename, indexname;"

    "CREATE TABLE temp.fkey2 AS SELECT "
        "fkid, from_tbl, to_tbl, sj(dq(to_col),',') AS cols "
        "FROM (SELECT * FROM temp.fkey ORDER BY to_col) " 
        "GROUP BY fkid, from_tbl;"
    , 0, 0, pzErr
  );
  if( rc!=SQLITE_OK ) return rc;
  rc = detectSchemaProblem(db, "foreign key is not unique",
    "SELECT fkid, from_tbl "
    "FROM temp.fkey2 "
    "WHERE NOT EXISTS (SELECT 1 "
        "FROM temp.idx WHERE tablename=to_tbl AND fkey2.cols==idx.cols"
    ")", pHasErrors
  );
  if( rc!=SQLITE_OK ) return rc;

  return rc;
}

int main(int argc, char **argv){
  sqlite3 *db;
  Options opt = {0, 0, 0};
  int rc;
  int hasErrors = 0;
  char *zErr = 0;
  const int enc = SQLITE_UTF8;

  const char *zSql =
    "SELECT multireplace('"

      "-- Triggers for foreign key mapping:\n"
      "--\n"
      "--     /from_readable/ REFERENCES /to_readable/\n"
      "--     on delete /on_delete/\n"
      "--     on update /on_update/\n"
      "--\n"

      /* The "BEFORE INSERT ON <referencing>" trigger. This trigger's job is to
      ** throw an exception if the user tries to insert a row into the
      ** referencing table for which there is no corresponding row in
      ** the referenced table.
      */
      "CREATE TRIGGER /name/_insert_referencing BEFORE INSERT ON /tbl/ WHEN \n"
      "    /key_notnull/ AND NOT EXISTS (SELECT 1 FROM /ref/ WHERE /cond1/)\n" 
      "BEGIN\n"
        "  SELECT RAISE(ABORT, ''constraint failed'');\n"
      "END;\n"

      /* The "BEFORE UPDATE ON <referencing>" trigger. This trigger's job 
      ** is to throw an exception if the user tries to update a row in the
      ** referencing table causing it to correspond to no row in the
      ** referenced table.
      */
      "CREATE TRIGGER /name/_update_referencing BEFORE\n"
      "    UPDATE OF /rkey_list/ ON /tbl/ WHEN \n"
      "    /key_notnull/ AND \n"
      "    NOT EXISTS (SELECT 1 FROM /ref/ WHERE /cond1/)\n" 
      "BEGIN\n"
        "  SELECT RAISE(ABORT, ''constraint failed'');\n"
      "END;\n"


      /* The "BEFORE DELETE ON <referenced>" trigger. This trigger's job 
      ** is to detect when a row is deleted from the referenced table to 
      ** which rows in the referencing table correspond. The action taken
      ** depends on the value of the 'ON DELETE' clause.
      */
      "CREATE TRIGGER /name/_delete_referenced BEFORE DELETE ON /ref/ WHEN\n"
      "    EXISTS (SELECT 1 FROM /tbl/ WHERE /cond2/)\n"
      "BEGIN\n"
      "  /delete_action/\n"
      "END;\n"

      /* The "BEFORE DELETE ON <referenced>" trigger. This trigger's job 
      ** is to detect when the key columns of a row in the referenced table 
      ** to which one or more rows in the referencing table correspond are
      ** updated. The action taken depends on the value of the 'ON UPDATE' 
      ** clause.
      */
      "CREATE TRIGGER /name/_update_referenced AFTER\n"
      "    UPDATE OF /fkey_list/ ON /ref/ WHEN \n"
      "    EXISTS (SELECT 1 FROM /tbl/ WHERE /cond2/)\n"
      "BEGIN\n"
      "  /update_action/\n"
      "END;\n"
    "'"

    /* These are used in the SQL comment written above each set of triggers */
    ", '/from_readable/',  from_tbl || '(' || sj(from_col, ', ') || ')'"
    ", '/to_readable/',    to_tbl || '(' || sj(to_col, ', ') || ')'"
    ", '/on_delete/', on_delete"
    ", '/on_update/', on_update"

    ", '/name/',   'genfkey' || min(rowid)"
    ", '/tbl/',    dq(from_tbl)"
    ", '/ref/',    dq(to_tbl)"
    ", '/key_notnull/', sj('new.' || dq(from_col) || ' IS NOT NULL', ' AND ')"

    ", '/fkey_list/', sj(to_col, ', ')"
    ", '/rkey_list/', sj(from_col, ', ')"

    ", '/cond1/',  sj(multireplace('new./from/ == /to/'"
                   ", '/from/', dq(from_col)"
                   ", '/to/',   dq(to_col)"
                   "), ' AND ')"
    ", '/cond2/',  sj(multireplace('old./to/ == /from/'"
                   ", '/from/', dq(from_col)"
                   ", '/to/',   dq(to_col)"
                   "), ' AND ')"

    ", '/update_action/', CASE on_update "
      "WHEN 'SET NULL' THEN "
        "multireplace('UPDATE /tbl/ SET /setlist/ WHERE /where/;' "
        ", '/setlist/', sj(from_col||' = NULL',', ')"
        ", '/tbl/',     dq(from_tbl)"
        ", '/where/',   sj(from_col||' = old.'||dq(to_col),' AND ')"
        ")"
      "WHEN 'CASCADE' THEN "
        "multireplace('UPDATE /tbl/ SET /setlist/ WHERE /where/;' "
        ", '/setlist/', sj(dq(from_col)||' = new.'||dq(to_col),', ')"
        ", '/tbl/',     dq(from_tbl)"
        ", '/where/',   sj(dq(from_col)||' = old.'||dq(to_col),' AND ')"
        ")"
      "ELSE "
      "  'SELECT RAISE(ABORT, ''constraint failed'');'"
      "END "

    ", '/delete_action/', CASE on_delete "
      "WHEN 'SET NULL' THEN "
        "multireplace('UPDATE /tbl/ SET /setlist/ WHERE /where/;' "
        ", '/setlist/', sj(from_col||' = NULL',', ')"
        ", '/tbl/',     dq(from_tbl)"
        ", '/where/',   sj(from_col||' = old.'||dq(to_col),' AND ')"
        ")"
      "WHEN 'CASCADE' THEN "
        "multireplace('DELETE FROM /tbl/ WHERE /where/;' "
        ", '/tbl/',     dq(from_tbl)"
        ", '/where/',   sj(dq(from_col)||' = old.'||dq(to_col),' AND ')"
        ")"
      "ELSE "
      "  'SELECT RAISE(ABORT, ''constraint failed'');'"
      "END "

    ") FROM temp.fkey "
    "GROUP BY from_tbl, fkid"
  ;

  processCmdLine(argc, argv, &opt);

  /* Open the database handle. */
  rc = sqlite3_open_v2(opt.zDb, &db, SQLITE_OPEN_READONLY, 0);
  if( rc!=SQLITE_OK ){
    fprintf(stderr, "Error opening database file: %s\n", sqlite3_errmsg(db));
    return -1;
  }

  /* Create the special scalar and aggregate functions used by this program. */
  sqlite3_create_function(db, "dq", 1, enc, 0, doublequote, 0, 0);
  sqlite3_create_function(db, "multireplace", -1, enc, db, multireplace, 0, 0);
  sqlite3_create_function(db, "sj", 2, enc, 0, 0, joinStep, joinFinalize);

  /* Install the "schema" virtual table module */
  installSchemaModule(db);

  /* Create and populate a temp table with the information required to
  ** build the foreign key triggers. See function populateTempTable()
  ** for details.
  */
  rc = populateTempTable(db, &zErr, &hasErrors);
  if( rc!=SQLITE_OK ){
    fprintf(stderr, "Error reading database: %s\n", zErr);
    return -1;
  }
  if( hasErrors && opt.ignoreErrors==0 ){
    return -1;
  }

  printf("BEGIN;\n");

  /* Unless the --no-drop option was specified, generate DROP TRIGGER
  ** statements to drop any triggers in the database generated by a
  ** previous run of this program.
  */
  if( opt.noDrop==0 ){
    rc = sqlite3_exec(db, 
      "SELECT 'DROP TRIGGER' || ' ' || dq(name) || ';'"
      "FROM sqlite_master "
      "WHERE type='trigger' AND substr(name, 0, 7) == 'genfkey'"
      , printString, 0, 0
    );
    if( rc!=SQLITE_OK ){
      const char *zMsg = sqlite3_errmsg(db);
      fprintf(stderr, "Generating drop triggers failed: %s\n", zMsg);
      return -1;
    }
  }

  /* Run the main query to create the trigger definitions. */
  rc = sqlite3_exec(db, zSql, printString, 0, 0);
  if( rc!=SQLITE_OK ){
    fprintf(stderr, "Generating triggers failed: %s\n", sqlite3_errmsg(db));
    return -1;
  }

  printf("COMMIT;\n");
  return 0;
}

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