ext/misc/dbdump.c

/*
** 2016-03-13
**
** 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 implements a C-language subroutine that converts the content
** of an SQLite database into UTF-8 text SQL statements that can be used
** to exactly recreate the original database.  ROWID values are preserved.
**
** A prototype of the implemented subroutine is this:
**
**   int sqlite3_db_dump(
**          sqlite3 *db,
**          const char *zSchema,
**          const char *zTable,
**          void (*xCallback)(void*, const char*),
**          void *pArg
**   );
**
** The db parameter is the database connection.  zSchema is the schema within
** that database which is to be dumped.  Usually the zSchema is "main" but
** can also be "temp" or any ATTACH-ed database.  If zTable is not NULL, then
** only the content of that one table is dumped.  If zTable is NULL, then all
** tables are dumped.
**
** The generate text is passed to xCallback() in multiple calls.  The second
** argument to xCallback() is a copy of the pArg parameter.  The first
** argument is some of the output text that this routine generates.  The
** signature to xCallback() is designed to make it compatible with fputs().
**
** The sqlite3_db_dump() subroutine returns SQLITE_OK on success or some error
** code if it encounters a problem.
**
** If this file is compiled with -DDBDUMP_STANDALONE then a "main()" routine
** is included so that this routine becomes a command-line utility.  The
** command-line utility takes two or three arguments which are the name
** of the database file, the schema, and optionally the table, forming the
** first three arguments of a single call to the library routine.
*/
#include "sqlite3.h"
#include <stdarg.h>
#include <string.h>
#include <ctype.h>

/*
** The state of the dump process.
*/
typedef struct DState DState;
struct DState {
  sqlite3 *db;                /* The database connection */
  int nErr;                   /* Number of errors seen so far */
  int rc;                     /* Error code */
  int writableSchema;                    /* True if in writable_schema mode */
  int (*xCallback)(const char*,void*);   /* Send output here */
  void *pArg;                            /* Argument to xCallback() */
};

/*
** A variable length string to which one can append text.
*/
typedef struct DText DText;
struct DText {
  char *z;           /* The text */
  int n;             /* Number of bytes of content in z[] */
  int nAlloc;        /* Number of bytes allocated to z[] */
};

/*
** Initialize and destroy a DText object
*/
static void initText(DText *p){
  memset(p, 0, sizeof(*p));
}
static void freeText(DText *p){
  sqlite3_free(p->z);
  initText(p);
}

/* zIn is either a pointer to a NULL-terminated string in memory obtained
** from malloc(), or a NULL pointer. The string pointed to by zAppend is
** added to zIn, and the result returned in memory obtained from malloc().
** zIn, if it was not NULL, is freed.
**
** If the third argument, quote, is not '\0', then it is used as a
** quote character for zAppend.
*/
static void appendText(DText *p, char const *zAppend, char quote){
  int len;
  int i;
  int nAppend = (int)(strlen(zAppend) & 0x3fffffff);

  len = nAppend+p->n+1;
  if( quote ){
    len += 2;
    for(i=0; i<nAppend; i++){
      if( zAppend[i]==quote ) len++;
    }
  }

  if( p->n+len>=p->nAlloc ){
    char *zNew;
    p->nAlloc = p->nAlloc*2 + len + 20;
    zNew = sqlite3_realloc(p->z, p->nAlloc);
    if( zNew==0 ){
      freeText(p);
      return;
    }
    p->z = zNew;
  }

  if( quote ){
    char *zCsr = p->z+p->n;
    *zCsr++ = quote;
    for(i=0; i<nAppend; i++){
      *zCsr++ = zAppend[i];
      if( zAppend[i]==quote ) *zCsr++ = quote;
    }
    *zCsr++ = quote;
    p->n = (int)(zCsr - p->z);
    *zCsr = '\0';
  }else{
    memcpy(p->z+p->n, zAppend, nAppend);
    p->n += nAppend;
    p->z[p->n] = '\0';
  }
}

/*
** Attempt to determine if identifier zName needs to be quoted, either
** because it contains non-alphanumeric characters, or because it is an
** SQLite keyword.  Be conservative in this estimate:  When in doubt assume
** that quoting is required.
**
** Return '"' if quoting is required.  Return 0 if no quoting is required.
*/
static char quoteChar(const char *zName){
  int i;
  if( !isalpha((unsigned char)zName[0]) && zName[0]!='_' ) return '"';
  for(i=0; zName[i]; i++){
    if( !isalnum((unsigned char)zName[i]) && zName[i]!='_' ) return '"';
  }
  return sqlite3_keyword_check(zName, i) ? '"' : 0;
}


/*
** Release memory previously allocated by tableColumnList().
*/
static void freeColumnList(char **azCol){
  int i;
  for(i=1; azCol[i]; i++){
    sqlite3_free(azCol[i]);
  }
  /* azCol[0] is a static string */
  sqlite3_free(azCol);
}

/*
** Return a list of pointers to strings which are the names of all
** columns in table zTab.   The memory to hold the names is dynamically
** allocated and must be released by the caller using a subsequent call
** to freeColumnList().
**
** The azCol[0] entry is usually NULL.  However, if zTab contains a rowid
** value that needs to be preserved, then azCol[0] is filled in with the
** name of the rowid column.
**
** The first regular column in the table is azCol[1].  The list is terminated
** by an entry with azCol[i]==0.
*/
static char **tableColumnList(DState *p, const char *zTab){
  char **azCol = 0;
  sqlite3_stmt *pStmt = 0;
  char *zSql;
  int nCol = 0;
  int nAlloc = 0;
  int nPK = 0;       /* Number of PRIMARY KEY columns seen */
  int isIPK = 0;     /* True if one PRIMARY KEY column of type INTEGER */
  int preserveRowid = 1;
  int rc;

  zSql = sqlite3_mprintf("PRAGMA table_info=%Q", zTab);
  if( zSql==0 ) return 0;
  rc = sqlite3_prepare_v2(p->db, zSql, -1, &pStmt, 0);
  sqlite3_free(zSql);
  if( rc ) return 0;
  while( sqlite3_step(pStmt)==SQLITE_ROW ){
    if( nCol>=nAlloc-2 ){
      char **azNew;
      nAlloc = nAlloc*2 + nCol + 10;
      azNew = sqlite3_realloc(azCol, nAlloc*sizeof(azCol[0]));
      if( azNew==0 ) goto col_oom;
      azCol = azNew;
      azCol[0] = 0;
    }
    azCol[++nCol] = sqlite3_mprintf("%s", sqlite3_column_text(pStmt, 1));
    if( azCol[nCol]==0 ) goto col_oom;
    if( sqlite3_column_int(pStmt, 5) ){
      nPK++;
      if( nPK==1
       && sqlite3_stricmp((const char*)sqlite3_column_text(pStmt,2),
                          "INTEGER")==0
      ){
        isIPK = 1;
      }else{
        isIPK = 0;
      }
    }
  }
  sqlite3_finalize(pStmt);
  pStmt = 0;
  azCol[nCol+1] = 0;

  /* The decision of whether or not a rowid really needs to be preserved
  ** is tricky.  We never need to preserve a rowid for a WITHOUT ROWID table
  ** or a table with an INTEGER PRIMARY KEY.  We are unable to preserve
  ** rowids on tables where the rowid is inaccessible because there are other
  ** columns in the table named "rowid", "_rowid_", and "oid".
  */
  if( isIPK ){
    /* If a single PRIMARY KEY column with type INTEGER was seen, then it
    ** might be an alise for the ROWID.  But it might also be a WITHOUT ROWID
    ** table or a INTEGER PRIMARY KEY DESC column, neither of which are
    ** ROWID aliases.  To distinguish these cases, check to see if
    ** there is a "pk" entry in "PRAGMA index_list".  There will be
    ** no "pk" index if the PRIMARY KEY really is an alias for the ROWID.
    */
    zSql = sqlite3_mprintf("SELECT 1 FROM pragma_index_list(%Q)"
                           " WHERE origin='pk'", zTab);
    if( zSql==0 ) goto col_oom;
    rc = sqlite3_prepare_v2(p->db, zSql, -1, &pStmt, 0);
    sqlite3_free(zSql);
    if( rc ){
      freeColumnList(azCol);
      return 0;
    }
    rc = sqlite3_step(pStmt);
    sqlite3_finalize(pStmt);
    pStmt = 0;
    preserveRowid = rc==SQLITE_ROW;
  }
  if( preserveRowid ){
    /* Only preserve the rowid if we can find a name to use for the
    ** rowid */
    static char *azRowid[] = { "rowid", "_rowid_", "oid" };
    int i, j;
    for(j=0; j<3; j++){
      for(i=1; i<=nCol; i++){
        if( sqlite3_stricmp(azRowid[j],azCol[i])==0 ) break;
      }
      if( i>nCol ){
        /* At this point, we know that azRowid[j] is not the name of any
        ** ordinary column in the table.  Verify that azRowid[j] is a valid
        ** name for the rowid before adding it to azCol[0].  WITHOUT ROWID
        ** tables will fail this last check */
        rc = sqlite3_table_column_metadata(p->db,0,zTab,azRowid[j],0,0,0,0,0);
        if( rc==SQLITE_OK ) azCol[0] = azRowid[j];
        break;
      }
    }
  }
  return azCol;

col_oom:
  sqlite3_finalize(pStmt);
  freeColumnList(azCol);
  p->nErr++;
  p->rc = SQLITE_NOMEM;
  return 0;
}

/*
** Send mprintf-formatted content to the output callback.
*/
static void output_formatted(DState *p, const char *zFormat, ...){
  va_list ap;
  char *z;
  va_start(ap, zFormat);
  z = sqlite3_vmprintf(zFormat, ap);
  va_end(ap);
  p->xCallback(z, p->pArg);
  sqlite3_free(z);
}

/*
** Find a string that is not found anywhere in z[].  Return a pointer
** to that string.
**
** Try to use zA and zB first.  If both of those are already found in z[]
** then make up some string and store it in the buffer zBuf.
*/
static const char *unused_string(
  const char *z,                    /* Result must not appear anywhere in z */
  const char *zA, const char *zB,   /* Try these first */
  char *zBuf                        /* Space to store a generated string */
){
  unsigned i = 0;
  if( strstr(z, zA)==0 ) return zA;
  if( strstr(z, zB)==0 ) return zB;
  do{
    sqlite3_snprintf(20,zBuf,"(%s%u)", zA, i++);
  }while( strstr(z,zBuf)!=0 );
  return zBuf;
}

/*
** Output the given string as a quoted string using SQL quoting conventions.
** Additionallly , escape the "\n" and "\r" characters so that they do not
** get corrupted by end-of-line translation facilities in some operating
** systems.
*/
static void output_quoted_escaped_string(DState *p, const char *z){
  int i;
  char c;
  for(i=0; (c = z[i])!=0 && c!='\'' && c!='\n' && c!='\r'; i++){}
  if( c==0 ){
    output_formatted(p,"'%s'",z);
  }else{
    const char *zNL = 0;
    const char *zCR = 0;
    int nNL = 0;
    int nCR = 0;
    char zBuf1[20], zBuf2[20];
    for(i=0; z[i]; i++){
      if( z[i]=='\n' ) nNL++;
      if( z[i]=='\r' ) nCR++;
    }
    if( nNL ){
      p->xCallback("replace(", p->pArg);
      zNL = unused_string(z, "\\n", "\\012", zBuf1);
    }
    if( nCR ){
      p->xCallback("replace(", p->pArg);
      zCR = unused_string(z, "\\r", "\\015", zBuf2);
    }
    p->xCallback("'", p->pArg);
    while( *z ){
      for(i=0; (c = z[i])!=0 && c!='\n' && c!='\r' && c!='\''; i++){}
      if( c=='\'' ) i++;
      if( i ){
        output_formatted(p, "%.*s", i, z);
        z += i;
      }
      if( c=='\'' ){
        p->xCallback("'", p->pArg);
        continue;
      }
      if( c==0 ){
        break;
      }
      z++;
      if( c=='\n' ){
        p->xCallback(zNL, p->pArg);
        continue;
      }
      p->xCallback(zCR, p->pArg);
    }
    p->xCallback("'", p->pArg);
    if( nCR ){
      output_formatted(p, ",'%s',char(13))", zCR);
    }
    if( nNL ){
      output_formatted(p, ",'%s',char(10))", zNL);
    }
  }
}

/*
** This is an sqlite3_exec callback routine used for dumping the database.
** Each row received by this callback consists of a table name,
** the table type ("index" or "table") and SQL to create the table.
** This routine should print text sufficient to recreate the table.
*/
static int dump_callback(void *pArg, int nArg, char **azArg, char **azCol){
  int rc;
  const char *zTable;
  const char *zType;
  const char *zSql;
  DState *p = (DState*)pArg;
  sqlite3_stmt *pStmt;

  (void)azCol;
  if( nArg!=3 ) return 1;
  zTable = azArg[0];
  zType = azArg[1];
  zSql = azArg[2];

  if( strcmp(zTable, "sqlite_sequence")==0 ){
    p->xCallback("DELETE FROM sqlite_sequence;\n", p->pArg);
  }else if( sqlite3_strglob("sqlite_stat?", zTable)==0 ){
    p->xCallback("ANALYZE sqlite_master;\n", p->pArg);
  }else if( strncmp(zTable, "sqlite_", 7)==0 ){
    return 0;
  }else if( strncmp(zSql, "CREATE VIRTUAL TABLE", 20)==0 ){
    if( !p->writableSchema ){
      p->xCallback("PRAGMA writable_schema=ON;\n", p->pArg);
      p->writableSchema = 1;
    }
    output_formatted(p,
       "INSERT INTO sqlite_master(type,name,tbl_name,rootpage,sql)"
       "VALUES('table','%q','%q',0,'%q');",
       zTable, zTable, zSql);
    return 0;
  }else{
    if( sqlite3_strglob("CREATE TABLE ['\"]*", zSql)==0 ){
      p->xCallback("CREATE TABLE IF NOT EXISTS ", p->pArg);
      p->xCallback(zSql+13, p->pArg);
    }else{
      p->xCallback(zSql, p->pArg);
    }
    p->xCallback(";\n", p->pArg);
  }

  if( strcmp(zType, "table")==0 ){
    DText sSelect;
    DText sTable;
    char **azTCol;
    int i;
    int nCol;

    azTCol = tableColumnList(p, zTable);
    if( azTCol==0 ) return 0;

    initText(&sTable);
    appendText(&sTable, "INSERT INTO ", 0);

    /* Always quote the table name, even if it appears to be pure ascii,
    ** in case it is a keyword. Ex:  INSERT INTO "table" ... */
    appendText(&sTable, zTable, quoteChar(zTable));

    /* If preserving the rowid, add a column list after the table name.
    ** In other words:  "INSERT INTO tab(rowid,a,b,c,...) VALUES(...)"
    ** instead of the usual "INSERT INTO tab VALUES(...)".
    */
    if( azTCol[0] ){
      appendText(&sTable, "(", 0);
      appendText(&sTable, azTCol[0], 0);
      for(i=1; azTCol[i]; i++){
        appendText(&sTable, ",", 0);
        appendText(&sTable, azTCol[i], quoteChar(azTCol[i]));
      }
      appendText(&sTable, ")", 0);
    }
    appendText(&sTable, " VALUES(", 0);

    /* Build an appropriate SELECT statement */
    initText(&sSelect);
    appendText(&sSelect, "SELECT ", 0);
    if( azTCol[0] ){
      appendText(&sSelect, azTCol[0], 0);
      appendText(&sSelect, ",", 0);
    }
    for(i=1; azTCol[i]; i++){
      appendText(&sSelect, azTCol[i], quoteChar(azTCol[i]));
      if( azTCol[i+1] ){
        appendText(&sSelect, ",", 0);
      }
    }
    nCol = i;
    if( azTCol[0]==0 ) nCol--;
    freeColumnList(azTCol);
    appendText(&sSelect, " FROM ", 0);
    appendText(&sSelect, zTable, quoteChar(zTable));

    rc = sqlite3_prepare_v2(p->db, sSelect.z, -1, &pStmt, 0);
    if( rc!=SQLITE_OK ){
      p->nErr++;
      if( p->rc==SQLITE_OK ) p->rc = rc;
    }else{
      while( SQLITE_ROW==sqlite3_step(pStmt) ){
        p->xCallback(sTable.z, p->pArg);
        for(i=0; i<nCol; i++){
          if( i ) p->xCallback(",", p->pArg);
          switch( sqlite3_column_type(pStmt,i) ){
            case SQLITE_INTEGER: {
              output_formatted(p, "%lld", sqlite3_column_int64(pStmt,i));
              break;
            }
            case SQLITE_FLOAT: {
              double r = sqlite3_column_double(pStmt,i);
              output_formatted(p, "%!.20g", r);
              break;
            }
            case SQLITE_NULL: {
              p->xCallback("NULL", p->pArg);
              break;
            }
            case SQLITE_TEXT: {
              output_quoted_escaped_string(p,
                   (const char*)sqlite3_column_text(pStmt,i));
              break;
            }
            case SQLITE_BLOB: {
              int nByte = sqlite3_column_bytes(pStmt,i);
              unsigned char *a = (unsigned char*)sqlite3_column_blob(pStmt,i);
              int j;
              p->xCallback("x'", p->pArg);
              for(j=0; j<nByte; j++){
                char zWord[3];
                zWord[0] = "0123456789abcdef"[(a[j]>>4)&15];
                zWord[1] = "0123456789abcdef"[a[j]&15];
                zWord[2] = 0;
                p->xCallback(zWord, p->pArg);
              }
              p->xCallback("'", p->pArg);
              break;
            }
          }
        }
        p->xCallback(");\n", p->pArg);
      }
    }
    sqlite3_finalize(pStmt);
    freeText(&sTable);
    freeText(&sSelect);
  }
  return 0;
}


/*
** Execute a query statement that will generate SQL output.  Print
** the result columns, comma-separated, on a line and then add a
** semicolon terminator to the end of that line.
**
** If the number of columns is 1 and that column contains text "--"
** then write the semicolon on a separate line.  That way, if a
** "--" comment occurs at the end of the statement, the comment
** won't consume the semicolon terminator.
*/
static void output_sql_from_query(
  DState *p,               /* Query context */
  const char *zSelect,     /* SELECT statement to extract content */
  ...
){
  sqlite3_stmt *pSelect;
  int rc;
  int nResult;
  int i;
  const char *z;
  char *zSql;
  va_list ap;
  va_start(ap, zSelect);
  zSql = sqlite3_vmprintf(zSelect, ap);
  va_end(ap);
  if( zSql==0 ){
    p->rc = SQLITE_NOMEM;
    p->nErr++;
    return;
  }
  rc = sqlite3_prepare_v2(p->db, zSql, -1, &pSelect, 0);
  sqlite3_free(zSql);
  if( rc!=SQLITE_OK || !pSelect ){
    output_formatted(p, "/**** ERROR: (%d) %s *****/\n", rc,
                sqlite3_errmsg(p->db));
    p->nErr++;
    return;
  }
  rc = sqlite3_step(pSelect);
  nResult = sqlite3_column_count(pSelect);
  while( rc==SQLITE_ROW ){
    z = (const char*)sqlite3_column_text(pSelect, 0);
    p->xCallback(z, p->pArg);
    for(i=1; i<nResult; i++){
      p->xCallback(",", p->pArg);
      p->xCallback((const char*)sqlite3_column_text(pSelect,i), p->pArg);
    }
    if( z==0 ) z = "";
    while( z[0] && (z[0]!='-' || z[1]!='-') ) z++;
    if( z[0] ){
      p->xCallback("\n;\n", p->pArg);
    }else{
      p->xCallback(";\n", p->pArg);
    }
    rc = sqlite3_step(pSelect);
  }
  rc = sqlite3_finalize(pSelect);
  if( rc!=SQLITE_OK ){
    output_formatted(p, "/**** ERROR: (%d) %s *****/\n", rc,
                     sqlite3_errmsg(p->db));
    if( (rc&0xff)!=SQLITE_CORRUPT ) p->nErr++;
  }
}

/*
** Run zQuery.  Use dump_callback() as the callback routine so that
** the contents of the query are output as SQL statements.
**
** If we get a SQLITE_CORRUPT error, rerun the query after appending
** "ORDER BY rowid DESC" to the end.
*/
static void run_schema_dump_query(
  DState *p,
  const char *zQuery,
  ...
){
  char *zErr = 0;
  char *z;
  va_list ap;
  va_start(ap, zQuery);
  z = sqlite3_vmprintf(zQuery, ap);
  va_end(ap);
  sqlite3_exec(p->db, z, dump_callback, p, &zErr);
  sqlite3_free(z);
  if( zErr ){
    output_formatted(p, "/****** %s ******/\n", zErr);
    sqlite3_free(zErr);
    p->nErr++;
    zErr = 0;
  }
}

/*
** Convert an SQLite database into SQL statements that will recreate that
** database.
*/
int sqlite3_db_dump(
  sqlite3 *db,               /* The database connection */
  const char *zSchema,       /* Which schema to dump.  Usually "main". */
  const char *zTable,        /* Which table to dump.  NULL means everything. */
  int (*xCallback)(const char*,void*),   /* Output sent to this callback */
  void *pArg                             /* Second argument of the callback */
){
  DState x;
  memset(&x, 0, sizeof(x));
  x.rc = sqlite3_exec(db, "BEGIN", 0, 0, 0);
  if( x.rc ) return x.rc;
  x.db = db;
  x.xCallback = xCallback;
  x.pArg = pArg;
  xCallback("PRAGMA foreign_keys=OFF;\nBEGIN TRANSACTION;\n", pArg);
  if( zTable==0 ){
    run_schema_dump_query(&x,
      "SELECT name, type, sql FROM \"%w\".sqlite_master "
      "WHERE sql NOT NULL AND type=='table' AND name!='sqlite_sequence'",
      zSchema
    );
    run_schema_dump_query(&x,
      "SELECT name, type, sql FROM \"%w\".sqlite_master "
      "WHERE name=='sqlite_sequence'", zSchema
    );
    output_sql_from_query(&x,
      "SELECT sql FROM sqlite_master "
      "WHERE sql NOT NULL AND type IN ('index','trigger','view')", 0
    );
  }else{
    run_schema_dump_query(&x,
      "SELECT name, type, sql FROM \"%w\".sqlite_master "
      "WHERE tbl_name=%Q COLLATE nocase AND type=='table'"
      "  AND sql NOT NULL",
      zSchema, zTable
    );
    output_sql_from_query(&x,
      "SELECT sql FROM \"%w\".sqlite_master "
      "WHERE sql NOT NULL"
      "  AND type IN ('index','trigger','view')"
      "  AND tbl_name=%Q COLLATE nocase",
      zSchema, zTable
    );
  }
  if( x.writableSchema ){
    xCallback("PRAGMA writable_schema=OFF;\n", pArg);
  }
  xCallback(x.nErr ? "ROLLBACK; -- due to errors\n" : "COMMIT;\n", pArg);
  sqlite3_exec(db, "COMMIT", 0, 0, 0);
  return x.rc;
}


/* The generic subroutine is above.  The code the follows implements
** the command-line interface.
*/
#ifdef DBDUMP_STANDALONE
#include <stdio.h>

/*
** Command-line interface
*/
int main(int argc, char **argv){
  sqlite3 *db;
  const char *zDb;
  const char *zSchema;
  const char *zTable = 0;
  int rc;

  if( argc<2 || argc>4 ){
    fprintf(stderr, "Usage: %s DATABASE ?SCHEMA? ?TABLE?\n", argv[0]);
    return 1;
  }
  zDb = argv[1];
  zSchema = argc>=3 ? argv[2] : "main";
  zTable = argc==4 ? argv[3] : 0;

  rc = sqlite3_open(zDb, &db);
  if( rc ){
    fprintf(stderr, "Cannot open \"%s\": %s\n", zDb, sqlite3_errmsg(db));
    sqlite3_close(db);
    return 1;
  }
  rc = sqlite3_db_dump(db, zSchema, zTable,
          (int(*)(const char*,void*))fputs, (void*)stdout);
  if( rc ){
    fprintf(stderr, "Error: sqlite3_db_dump() returns %d\n", rc);
  }
  sqlite3_close(db);
  return rc!=SQLITE_OK;
}
#endif /* DBDUMP_STANDALONE */