/*
** 2017-10-11
**
** 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 an implementation of the "sqlite_dbpage" virtual table.
**
** The sqlite_dbpage virtual table is used to read or write whole raw
** pages of the database file. The pager interface is used so that
** uncommitted changes and changes recorded in the WAL file are correctly
** retrieved.
**
** Usage example:
**
** SELECT data FROM sqlite_dbpage('aux1') WHERE pgno=123;
**
** This is an eponymous virtual table so it does not need to be created before
** use. The optional argument to the sqlite_dbpage() table name is the
** schema for the database file that is to be read. The default schema is
** "main".
**
** The data field of sqlite_dbpage table can be updated. The new
** value must be a BLOB which is the correct page size, otherwise the
** update fails. Rows may not be deleted or inserted.
*/
#include "sqliteInt.h" /* Requires access to internal data structures */
#if (defined(SQLITE_ENABLE_DBPAGE_VTAB) || defined(SQLITE_TEST)) \
&& !defined(SQLITE_OMIT_VIRTUALTABLE)
typedef struct DbpageTable DbpageTable;
typedef struct DbpageCursor DbpageCursor;
struct DbpageCursor {
sqlite3_vtab_cursor base; /* Base class. Must be first */
int pgno; /* Current page number */
int mxPgno; /* Last page to visit on this scan */
};
struct DbpageTable {
sqlite3_vtab base; /* Base class. Must be first */
sqlite3 *db; /* The database */
Pager *pPager; /* Pager being read/written */
int iDb; /* Index of database to analyze */
int szPage; /* Size of each page in bytes */
int nPage; /* Number of pages in the file */
};
/*
** Connect to or create a dbpagevfs virtual table.
*/
static int dbpageConnect(
sqlite3 *db,
void *pAux,
int argc, const char *const*argv,
sqlite3_vtab **ppVtab,
char **pzErr
){
DbpageTable *pTab = 0;
int rc = SQLITE_OK;
int iDb;
if( argc>=4 ){
Token nm;
sqlite3TokenInit(&nm, (char*)argv[3]);
iDb = sqlite3FindDb(db, &nm);
if( iDb<0 ){
*pzErr = sqlite3_mprintf("no such schema: %s", argv[3]);
return SQLITE_ERROR;
}
}else{
iDb = 0;
}
rc = sqlite3_declare_vtab(db,
"CREATE TABLE x(pgno INTEGER PRIMARY KEY, data BLOB, schema HIDDEN)");
if( rc==SQLITE_OK ){
pTab = (DbpageTable *)sqlite3_malloc64(sizeof(DbpageTable));
if( pTab==0 ) rc = SQLITE_NOMEM_BKPT;
}
assert( rc==SQLITE_OK || pTab==0 );
if( rc==SQLITE_OK ){
Btree *pBt = db->aDb[iDb].pBt;
memset(pTab, 0, sizeof(DbpageTable));
pTab->db = db;
pTab->iDb = iDb;
pTab->pPager = pBt ? sqlite3BtreePager(pBt) : 0;
}
*ppVtab = (sqlite3_vtab*)pTab;
return rc;
}
/*
** Disconnect from or destroy a dbpagevfs virtual table.
*/
static int dbpageDisconnect(sqlite3_vtab *pVtab){
sqlite3_free(pVtab);
return SQLITE_OK;
}
/*
** idxNum:
**
** 0 full table scan
** 1 pgno=?1
*/
static int dbpageBestIndex(sqlite3_vtab *tab, sqlite3_index_info *pIdxInfo){
int i;
pIdxInfo->estimatedCost = 1.0e6; /* Initial cost estimate */
for(i=0; i<pIdxInfo->nConstraint; i++){
struct sqlite3_index_constraint *p = &pIdxInfo->aConstraint[i];
if( p->usable && p->iColumn<=0 && p->op==SQLITE_INDEX_CONSTRAINT_EQ ){
pIdxInfo->estimatedRows = 1;
pIdxInfo->idxFlags = SQLITE_INDEX_SCAN_UNIQUE;
pIdxInfo->estimatedCost = 1.0;
pIdxInfo->idxNum = 1;
pIdxInfo->aConstraintUsage[i].argvIndex = 1;
pIdxInfo->aConstraintUsage[i].omit = 1;
break;
}
}
if( pIdxInfo->nOrderBy>=1
&& pIdxInfo->aOrderBy[0].iColumn<=0
&& pIdxInfo->aOrderBy[0].desc==0
){
pIdxInfo->orderByConsumed = 1;
}
return SQLITE_OK;
}
/*
** Open a new dbpagevfs cursor.
*/
static int dbpageOpen(sqlite3_vtab *pVTab, sqlite3_vtab_cursor **ppCursor){
DbpageCursor *pCsr;
pCsr = (DbpageCursor *)sqlite3_malloc64(sizeof(DbpageCursor));
if( pCsr==0 ){
return SQLITE_NOMEM_BKPT;
}else{
memset(pCsr, 0, sizeof(DbpageCursor));
pCsr->base.pVtab = pVTab;
pCsr->pgno = -1;
}
*ppCursor = (sqlite3_vtab_cursor *)pCsr;
return SQLITE_OK;
}
/*
** Close a dbpagevfs cursor.
*/
static int dbpageClose(sqlite3_vtab_cursor *pCursor){
DbpageCursor *pCsr = (DbpageCursor *)pCursor;
sqlite3_free(pCsr);
return SQLITE_OK;
}
/*
** Move a dbpagevfs cursor to the next entry in the file.
*/
static int dbpageNext(sqlite3_vtab_cursor *pCursor){
int rc = SQLITE_OK;
DbpageCursor *pCsr = (DbpageCursor *)pCursor;
pCsr->pgno++;
return rc;
}
static int dbpageEof(sqlite3_vtab_cursor *pCursor){
DbpageCursor *pCsr = (DbpageCursor *)pCursor;
return pCsr->pgno > pCsr->mxPgno;
}
static int dbpageFilter(
sqlite3_vtab_cursor *pCursor,
int idxNum, const char *idxStr,
int argc, sqlite3_value **argv
){
DbpageCursor *pCsr = (DbpageCursor *)pCursor;
DbpageTable *pTab = (DbpageTable *)pCursor->pVtab;
int rc = SQLITE_OK;
Btree *pBt = pTab->db->aDb[pTab->iDb].pBt;
pTab->szPage = sqlite3BtreeGetPageSize(pBt);
pTab->nPage = sqlite3BtreeLastPage(pBt);
if( idxNum==1 ){
pCsr->pgno = sqlite3_value_int(argv[0]);
if( pCsr->pgno<1 || pCsr->pgno>pTab->nPage ){
pCsr->pgno = 1;
pCsr->mxPgno = 0;
}else{
pCsr->mxPgno = pCsr->pgno;
}
}else{
pCsr->pgno = 1;
pCsr->mxPgno = pTab->nPage;
}
return rc;
}
static int dbpageColumn(
sqlite3_vtab_cursor *pCursor,
sqlite3_context *ctx,
int i
){
DbpageCursor *pCsr = (DbpageCursor *)pCursor;
DbpageTable *pTab = (DbpageTable *)pCursor->pVtab;
int rc = SQLITE_OK;
switch( i ){
case 0: { /* pgno */
sqlite3_result_int(ctx, pCsr->pgno);
break;
}
case 1: { /* data */
DbPage *pDbPage = 0;
rc = sqlite3PagerGet(pTab->pPager, pCsr->pgno, (DbPage**)&pDbPage, 0);
if( rc==SQLITE_OK ){
sqlite3_result_blob(ctx, sqlite3PagerGetData(pDbPage), pTab->szPage,
SQLITE_TRANSIENT);
}
sqlite3PagerUnref(pDbPage);
break;
}
default: { /* schema */
sqlite3 *db = sqlite3_context_db_handle(ctx);
sqlite3_result_text(ctx, db->aDb[pTab->iDb].zDbSName, -1, SQLITE_STATIC);
break;
}
}
return SQLITE_OK;
}
static int dbpageRowid(sqlite3_vtab_cursor *pCursor, sqlite_int64 *pRowid){
DbpageCursor *pCsr = (DbpageCursor *)pCursor;
*pRowid = pCsr->pgno;
return SQLITE_OK;
}
static int dbpageUpdate(
sqlite3_vtab *pVtab,
int argc,
sqlite3_value **argv,
sqlite_int64 *pRowid
){
DbpageTable *pTab = (DbpageTable *)pVtab;
int pgno;
DbPage *pDbPage = 0;
int rc = SQLITE_OK;
char *zErr = 0;
if( argc==1 ){
zErr = "cannot delete";
goto update_fail;
}
pgno = sqlite3_value_int(argv[0]);
if( pgno<1 || pgno>pTab->nPage ){
zErr = "bad page number";
goto update_fail;
}
if( sqlite3_value_int(argv[1])!=pgno ){
zErr = "cannot insert";
goto update_fail;
}
if( sqlite3_value_type(argv[3])!=SQLITE_BLOB
|| sqlite3_value_bytes(argv[3])!=pTab->szPage
){
zErr = "bad page value";
goto update_fail;
}
rc = sqlite3PagerGet(pTab->pPager, pgno, (DbPage**)&pDbPage, 0);
if( rc==SQLITE_OK ){
rc = sqlite3PagerWrite(pDbPage);
if( rc==SQLITE_OK ){
memcpy(sqlite3PagerGetData(pDbPage),
sqlite3_value_blob(argv[3]),
pTab->szPage);
}
}
sqlite3PagerUnref(pDbPage);
return rc;
update_fail:
sqlite3_free(pVtab->zErrMsg);
pVtab->zErrMsg = sqlite3_mprintf("%s", zErr);
return SQLITE_ERROR;
}
/*
** Invoke this routine to register the "dbpage" virtual table module
*/
int sqlite3DbpageRegister(sqlite3 *db){
static sqlite3_module dbpage_module = {
0, /* iVersion */
dbpageConnect, /* xCreate */
dbpageConnect, /* xConnect */
dbpageBestIndex, /* xBestIndex */
dbpageDisconnect, /* xDisconnect */
dbpageDisconnect, /* xDestroy */
dbpageOpen, /* xOpen - open a cursor */
dbpageClose, /* xClose - close a cursor */
dbpageFilter, /* xFilter - configure scan constraints */
dbpageNext, /* xNext - advance a cursor */
dbpageEof, /* xEof - check for end of scan */
dbpageColumn, /* xColumn - read data */
dbpageRowid, /* xRowid - read data */
dbpageUpdate, /* xUpdate */
0, /* xBegin */
0, /* xSync */
0, /* xCommit */
0, /* xRollback */
0, /* xFindMethod */
0, /* xRename */
0, /* xSavepoint */
0, /* xRelease */
0, /* xRollbackTo */
};
return sqlite3_create_module(db, "sqlite_dbpage", &dbpage_module, 0);
}
#elif defined(SQLITE_ENABLE_DBPAGE_VTAB)
int sqlite3DbpageRegister(sqlite3 *db){ return SQLITE_OK; }
#endif /* SQLITE_ENABLE_DBSTAT_VTAB */