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Diffstat (limited to '')
| -rw-r--r-- | ext/misc/btreeinfo.c | 429 |
1 files changed, 429 insertions, 0 deletions
diff --git a/ext/misc/btreeinfo.c b/ext/misc/btreeinfo.c new file mode 100644 index 0000000..22f8268 --- /dev/null +++ b/ext/misc/btreeinfo.c @@ -0,0 +1,429 @@ +/* +** 2017-10-24 +** +** 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_btreeinfo" virtual table. +** +** The sqlite_btreeinfo virtual table is a read-only eponymous-only virtual +** table that shows information about all btrees in an SQLite database file. +** The schema is like this: +** +** CREATE TABLE sqlite_btreeinfo( +** type TEXT, -- "table" or "index" +** name TEXT, -- Name of table or index for this btree. +** tbl_name TEXT, -- Associated table +** rootpage INT, -- The root page of the btree +** sql TEXT, -- SQL for this btree - from sqlite_schema +** hasRowid BOOLEAN, -- True if the btree has a rowid +** nEntry INT, -- Estimated number of entries +** nPage INT, -- Estimated number of pages +** depth INT, -- Depth of the btree +** szPage INT, -- Size of each page in bytes +** zSchema TEXT HIDDEN -- The schema to which this btree belongs +** ); +** +** The first 5 fields are taken directly from the sqlite_schema table. +** Considering only the first 5 fields, the only difference between +** this virtual table and the sqlite_schema table is that this virtual +** table omits all entries that have a 0 or NULL rowid - in other words +** it omits triggers and views. +** +** The value added by this table comes in the next 5 fields. +** +** Note that nEntry and nPage are *estimated*. They are computed doing +** a single search from the root to a leaf, counting the number of cells +** at each level, and assuming that unvisited pages have a similar number +** of cells. +** +** The sqlite_dbpage virtual table must be available for this virtual table +** to operate. +** +** USAGE EXAMPLES: +** +** Show the table btrees in a schema order with the tables with the most +** rows occuring first: +** +** SELECT name, nEntry +** FROM sqlite_btreeinfo +** WHERE type='table' +** ORDER BY nEntry DESC, name; +** +** Show the names of all WITHOUT ROWID tables: +** +** SELECT name FROM sqlite_btreeinfo +** WHERE type='table' AND NOT hasRowid; +*/ +#if !defined(SQLITEINT_H) +#include "sqlite3ext.h" +#endif +SQLITE_EXTENSION_INIT1 +#include <string.h> +#include <assert.h> + +/* Columns available in this virtual table */ +#define BINFO_COLUMN_TYPE 0 +#define BINFO_COLUMN_NAME 1 +#define BINFO_COLUMN_TBL_NAME 2 +#define BINFO_COLUMN_ROOTPAGE 3 +#define BINFO_COLUMN_SQL 4 +#define BINFO_COLUMN_HASROWID 5 +#define BINFO_COLUMN_NENTRY 6 +#define BINFO_COLUMN_NPAGE 7 +#define BINFO_COLUMN_DEPTH 8 +#define BINFO_COLUMN_SZPAGE 9 +#define BINFO_COLUMN_SCHEMA 10 + +/* Forward declarations */ +typedef struct BinfoTable BinfoTable; +typedef struct BinfoCursor BinfoCursor; + +/* A cursor for the sqlite_btreeinfo table */ +struct BinfoCursor { + sqlite3_vtab_cursor base; /* Base class. Must be first */ + sqlite3_stmt *pStmt; /* Query against sqlite_schema */ + int rc; /* Result of previous sqlite_step() call */ + int hasRowid; /* hasRowid value. Negative if unknown. */ + sqlite3_int64 nEntry; /* nEntry value */ + int nPage; /* nPage value */ + int depth; /* depth value */ + int szPage; /* size of a btree page. 0 if unknown */ + char *zSchema; /* Schema being interrogated */ +}; + +/* The sqlite_btreeinfo table */ +struct BinfoTable { + sqlite3_vtab base; /* Base class. Must be first */ + sqlite3 *db; /* The databse connection */ +}; + +/* +** Connect to the sqlite_btreeinfo virtual table. +*/ +static int binfoConnect( + sqlite3 *db, + void *pAux, + int argc, const char *const*argv, + sqlite3_vtab **ppVtab, + char **pzErr +){ + BinfoTable *pTab = 0; + int rc = SQLITE_OK; + rc = sqlite3_declare_vtab(db, + "CREATE TABLE x(\n" + " type TEXT,\n" + " name TEXT,\n" + " tbl_name TEXT,\n" + " rootpage INT,\n" + " sql TEXT,\n" + " hasRowid BOOLEAN,\n" + " nEntry INT,\n" + " nPage INT,\n" + " depth INT,\n" + " szPage INT,\n" + " zSchema TEXT HIDDEN\n" + ")"); + if( rc==SQLITE_OK ){ + pTab = (BinfoTable *)sqlite3_malloc64(sizeof(BinfoTable)); + if( pTab==0 ) rc = SQLITE_NOMEM; + } + assert( rc==SQLITE_OK || pTab==0 ); + if( pTab ){ + pTab->db = db; + } + *ppVtab = (sqlite3_vtab*)pTab; + return rc; +} + +/* +** Disconnect from or destroy a btreeinfo virtual table. +*/ +static int binfoDisconnect(sqlite3_vtab *pVtab){ + sqlite3_free(pVtab); + return SQLITE_OK; +} + +/* +** idxNum: +** +** 0 Use "main" for the schema +** 1 Schema identified by parameter ?1 +*/ +static int binfoBestIndex(sqlite3_vtab *tab, sqlite3_index_info *pIdxInfo){ + int i; + pIdxInfo->estimatedCost = 10000.0; /* Cost estimate */ + pIdxInfo->estimatedRows = 100; + for(i=0; i<pIdxInfo->nConstraint; i++){ + struct sqlite3_index_constraint *p = &pIdxInfo->aConstraint[i]; + if( p->usable + && p->iColumn==BINFO_COLUMN_SCHEMA + && p->op==SQLITE_INDEX_CONSTRAINT_EQ + ){ + pIdxInfo->estimatedCost = 1000.0; + pIdxInfo->idxNum = 1; + pIdxInfo->aConstraintUsage[i].argvIndex = 1; + pIdxInfo->aConstraintUsage[i].omit = 1; + break; + } + } + return SQLITE_OK; +} + +/* +** Open a new btreeinfo cursor. +*/ +static int binfoOpen(sqlite3_vtab *pVTab, sqlite3_vtab_cursor **ppCursor){ + BinfoCursor *pCsr; + + pCsr = (BinfoCursor *)sqlite3_malloc64(sizeof(BinfoCursor)); + if( pCsr==0 ){ + return SQLITE_NOMEM; + }else{ + memset(pCsr, 0, sizeof(BinfoCursor)); + pCsr->base.pVtab = pVTab; + } + + *ppCursor = (sqlite3_vtab_cursor *)pCsr; + return SQLITE_OK; +} + +/* +** Close a btreeinfo cursor. +*/ +static int binfoClose(sqlite3_vtab_cursor *pCursor){ + BinfoCursor *pCsr = (BinfoCursor *)pCursor; + sqlite3_finalize(pCsr->pStmt); + sqlite3_free(pCsr->zSchema); + sqlite3_free(pCsr); + return SQLITE_OK; +} + +/* +** Move a btreeinfo cursor to the next entry in the file. +*/ +static int binfoNext(sqlite3_vtab_cursor *pCursor){ + BinfoCursor *pCsr = (BinfoCursor *)pCursor; + pCsr->rc = sqlite3_step(pCsr->pStmt); + pCsr->hasRowid = -1; + return pCsr->rc==SQLITE_ERROR ? SQLITE_ERROR : SQLITE_OK; +} + +/* We have reached EOF if previous sqlite3_step() returned +** anything other than SQLITE_ROW; +*/ +static int binfoEof(sqlite3_vtab_cursor *pCursor){ + BinfoCursor *pCsr = (BinfoCursor *)pCursor; + return pCsr->rc!=SQLITE_ROW; +} + +/* Position a cursor back to the beginning. +*/ +static int binfoFilter( + sqlite3_vtab_cursor *pCursor, + int idxNum, const char *idxStr, + int argc, sqlite3_value **argv +){ + BinfoCursor *pCsr = (BinfoCursor *)pCursor; + BinfoTable *pTab = (BinfoTable *)pCursor->pVtab; + char *zSql; + int rc; + + sqlite3_free(pCsr->zSchema); + if( idxNum==1 && sqlite3_value_type(argv[0])!=SQLITE_NULL ){ + pCsr->zSchema = sqlite3_mprintf("%s", sqlite3_value_text(argv[0])); + }else{ + pCsr->zSchema = sqlite3_mprintf("main"); + } + zSql = sqlite3_mprintf( + "SELECT 0, 'table','sqlite_schema','sqlite_schema',1,NULL " + "UNION ALL " + "SELECT rowid, type, name, tbl_name, rootpage, sql" + " FROM \"%w\".sqlite_schema WHERE rootpage>=1", + pCsr->zSchema); + sqlite3_finalize(pCsr->pStmt); + pCsr->pStmt = 0; + pCsr->hasRowid = -1; + rc = sqlite3_prepare_v2(pTab->db, zSql, -1, &pCsr->pStmt, 0); + sqlite3_free(zSql); + if( rc==SQLITE_OK ){ + rc = binfoNext(pCursor); + } + return rc; +} + +/* Decode big-endian integers */ +static unsigned int get_uint16(unsigned char *a){ + return (a[0]<<8)|a[1]; +} +static unsigned int get_uint32(unsigned char *a){ + return (a[0]<<24)|(a[1]<<16)|(a[2]<<8)|a[3]; +} + +/* Examine the b-tree rooted at pgno and estimate its size. +** Return non-zero if anything goes wrong. +*/ +static int binfoCompute(sqlite3 *db, int pgno, BinfoCursor *pCsr){ + sqlite3_int64 nEntry = 1; + int nPage = 1; + unsigned char *aData; + sqlite3_stmt *pStmt = 0; + int rc = SQLITE_OK; + int pgsz = 0; + int nCell; + int iCell; + + rc = sqlite3_prepare_v2(db, + "SELECT data FROM sqlite_dbpage('main') WHERE pgno=?1", -1, + &pStmt, 0); + if( rc ) return rc; + pCsr->depth = 1; + while(1){ + sqlite3_bind_int(pStmt, 1, pgno); + rc = sqlite3_step(pStmt); + if( rc!=SQLITE_ROW ){ + rc = SQLITE_ERROR; + break; + } + pCsr->szPage = pgsz = sqlite3_column_bytes(pStmt, 0); + aData = (unsigned char*)sqlite3_column_blob(pStmt, 0); + if( aData==0 ){ + rc = SQLITE_NOMEM; + break; + } + if( pgno==1 ){ + aData += 100; + pgsz -= 100; + } + pCsr->hasRowid = aData[0]!=2 && aData[0]!=10; + nCell = get_uint16(aData+3); + nEntry *= (nCell+1); + if( aData[0]==10 || aData[0]==13 ) break; + nPage *= (nCell+1); + if( nCell<=1 ){ + pgno = get_uint32(aData+8); + }else{ + iCell = get_uint16(aData+12+2*(nCell/2)); + if( pgno==1 ) iCell -= 100; + if( iCell<=12 || iCell>=pgsz-4 ){ + rc = SQLITE_CORRUPT; + break; + } + pgno = get_uint32(aData+iCell); + } + pCsr->depth++; + sqlite3_reset(pStmt); + } + sqlite3_finalize(pStmt); + pCsr->nPage = nPage; + pCsr->nEntry = nEntry; + if( rc==SQLITE_ROW ) rc = SQLITE_OK; + return rc; +} + +/* Return a column for the sqlite_btreeinfo table */ +static int binfoColumn( + sqlite3_vtab_cursor *pCursor, + sqlite3_context *ctx, + int i +){ + BinfoCursor *pCsr = (BinfoCursor *)pCursor; + if( i>=BINFO_COLUMN_HASROWID && i<=BINFO_COLUMN_SZPAGE && pCsr->hasRowid<0 ){ + int pgno = sqlite3_column_int(pCsr->pStmt, BINFO_COLUMN_ROOTPAGE+1); + sqlite3 *db = sqlite3_context_db_handle(ctx); + int rc = binfoCompute(db, pgno, pCsr); + if( rc ){ + pCursor->pVtab->zErrMsg = sqlite3_mprintf("%s", sqlite3_errmsg(db)); + return SQLITE_ERROR; + } + } + switch( i ){ + case BINFO_COLUMN_NAME: + case BINFO_COLUMN_TYPE: + case BINFO_COLUMN_TBL_NAME: + case BINFO_COLUMN_ROOTPAGE: + case BINFO_COLUMN_SQL: { + sqlite3_result_value(ctx, sqlite3_column_value(pCsr->pStmt, i+1)); + break; + } + case BINFO_COLUMN_HASROWID: { + sqlite3_result_int(ctx, pCsr->hasRowid); + break; + } + case BINFO_COLUMN_NENTRY: { + sqlite3_result_int64(ctx, pCsr->nEntry); + break; + } + case BINFO_COLUMN_NPAGE: { + sqlite3_result_int(ctx, pCsr->nPage); + break; + } + case BINFO_COLUMN_DEPTH: { + sqlite3_result_int(ctx, pCsr->depth); + break; + } + case BINFO_COLUMN_SCHEMA: { + sqlite3_result_text(ctx, pCsr->zSchema, -1, SQLITE_STATIC); + break; + } + } + return SQLITE_OK; +} + +/* Return the ROWID for the sqlite_btreeinfo table */ +static int binfoRowid(sqlite3_vtab_cursor *pCursor, sqlite_int64 *pRowid){ + BinfoCursor *pCsr = (BinfoCursor *)pCursor; + *pRowid = sqlite3_column_int64(pCsr->pStmt, 0); + return SQLITE_OK; +} + +/* +** Invoke this routine to register the "sqlite_btreeinfo" virtual table module +*/ +int sqlite3BinfoRegister(sqlite3 *db){ + static sqlite3_module binfo_module = { + 0, /* iVersion */ + 0, /* xCreate */ + binfoConnect, /* xConnect */ + binfoBestIndex, /* xBestIndex */ + binfoDisconnect, /* xDisconnect */ + 0, /* xDestroy */ + binfoOpen, /* xOpen - open a cursor */ + binfoClose, /* xClose - close a cursor */ + binfoFilter, /* xFilter - configure scan constraints */ + binfoNext, /* xNext - advance a cursor */ + binfoEof, /* xEof - check for end of scan */ + binfoColumn, /* xColumn - read data */ + binfoRowid, /* xRowid - read data */ + 0, /* xUpdate */ + 0, /* xBegin */ + 0, /* xSync */ + 0, /* xCommit */ + 0, /* xRollback */ + 0, /* xFindMethod */ + 0, /* xRename */ + 0, /* xSavepoint */ + 0, /* xRelease */ + 0, /* xRollbackTo */ + 0 /* xShadowName */ + }; + return sqlite3_create_module(db, "sqlite_btreeinfo", &binfo_module, 0); +} + +#ifdef _WIN32 +__declspec(dllexport) +#endif +int sqlite3_btreeinfo_init( + sqlite3 *db, + char **pzErrMsg, + const sqlite3_api_routines *pApi +){ + SQLITE_EXTENSION_INIT2(pApi); + return sqlite3BinfoRegister(db); +} |