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diff --git a/ext/misc/completion.c b/ext/misc/completion.c
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+/*
+** 2017-07-10
+**
+** 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 implements an eponymous virtual table that returns suggested
+** completions for a partial SQL input.
+**
+** Suggested usage:
+**
+** SELECT DISTINCT candidate COLLATE nocase
+** FROM completion($prefix,$wholeline)
+** ORDER BY 1;
+**
+** The two query parameters are optional. $prefix is the text of the
+** current word being typed and that is to be completed. $wholeline is
+** the complete input line, used for context.
+**
+** The raw completion() table might return the same candidate multiple
+** times, for example if the same column name is used to two or more
+** tables. And the candidates are returned in an arbitrary order. Hence,
+** the DISTINCT and ORDER BY are recommended.
+**
+** This virtual table operates at the speed of human typing, and so there
+** is no attempt to make it fast. Even a slow implementation will be much
+** faster than any human can type.
+**
+*/
+#include "sqlite3ext.h"
+SQLITE_EXTENSION_INIT1
+#include <assert.h>
+#include <string.h>
+#include <ctype.h>
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+
+/* completion_vtab is a subclass of sqlite3_vtab which will
+** serve as the underlying representation of a completion virtual table
+*/
+typedef struct completion_vtab completion_vtab;
+struct completion_vtab {
+ sqlite3_vtab base; /* Base class - must be first */
+ sqlite3 *db; /* Database connection for this completion vtab */
+};
+
+/* completion_cursor is a subclass of sqlite3_vtab_cursor which will
+** serve as the underlying representation of a cursor that scans
+** over rows of the result
+*/
+typedef struct completion_cursor completion_cursor;
+struct completion_cursor {
+ sqlite3_vtab_cursor base; /* Base class - must be first */
+ sqlite3 *db; /* Database connection for this cursor */
+ int nPrefix, nLine; /* Number of bytes in zPrefix and zLine */
+ char *zPrefix; /* The prefix for the word we want to complete */
+ char *zLine; /* The whole that we want to complete */
+ const char *zCurrentRow; /* Current output row */
+ int szRow; /* Length of the zCurrentRow string */
+ sqlite3_stmt *pStmt; /* Current statement */
+ sqlite3_int64 iRowid; /* The rowid */
+ int ePhase; /* Current phase */
+ int j; /* inter-phase counter */
+};
+
+/* Values for ePhase:
+*/
+#define COMPLETION_FIRST_PHASE 1
+#define COMPLETION_KEYWORDS 1
+#define COMPLETION_PRAGMAS 2
+#define COMPLETION_FUNCTIONS 3
+#define COMPLETION_COLLATIONS 4
+#define COMPLETION_INDEXES 5
+#define COMPLETION_TRIGGERS 6
+#define COMPLETION_DATABASES 7
+#define COMPLETION_TABLES 8 /* Also VIEWs and TRIGGERs */
+#define COMPLETION_COLUMNS 9
+#define COMPLETION_MODULES 10
+#define COMPLETION_EOF 11
+
+/*
+** The completionConnect() method is invoked to create a new
+** completion_vtab that describes the completion virtual table.
+**
+** Think of this routine as the constructor for completion_vtab objects.
+**
+** All this routine needs to do is:
+**
+** (1) Allocate the completion_vtab object and initialize all fields.
+**
+** (2) Tell SQLite (via the sqlite3_declare_vtab() interface) what the
+** result set of queries against completion will look like.
+*/
+static int completionConnect(
+ sqlite3 *db,
+ void *pAux,
+ int argc, const char *const*argv,
+ sqlite3_vtab **ppVtab,
+ char **pzErr
+){
+ completion_vtab *pNew;
+ int rc;
+
+ (void)(pAux); /* Unused parameter */
+ (void)(argc); /* Unused parameter */
+ (void)(argv); /* Unused parameter */
+ (void)(pzErr); /* Unused parameter */
+
+/* Column numbers */
+#define COMPLETION_COLUMN_CANDIDATE 0 /* Suggested completion of the input */
+#define COMPLETION_COLUMN_PREFIX 1 /* Prefix of the word to be completed */
+#define COMPLETION_COLUMN_WHOLELINE 2 /* Entire line seen so far */
+#define COMPLETION_COLUMN_PHASE 3 /* ePhase - used for debugging only */
+
+ sqlite3_vtab_config(db, SQLITE_VTAB_INNOCUOUS);
+ rc = sqlite3_declare_vtab(db,
+ "CREATE TABLE x("
+ " candidate TEXT,"
+ " prefix TEXT HIDDEN,"
+ " wholeline TEXT HIDDEN,"
+ " phase INT HIDDEN" /* Used for debugging only */
+ ")");
+ if( rc==SQLITE_OK ){
+ pNew = sqlite3_malloc( sizeof(*pNew) );
+ *ppVtab = (sqlite3_vtab*)pNew;
+ if( pNew==0 ) return SQLITE_NOMEM;
+ memset(pNew, 0, sizeof(*pNew));
+ pNew->db = db;
+ }
+ return rc;
+}
+
+/*
+** This method is the destructor for completion_cursor objects.
+*/
+static int completionDisconnect(sqlite3_vtab *pVtab){
+ sqlite3_free(pVtab);
+ return SQLITE_OK;
+}
+
+/*
+** Constructor for a new completion_cursor object.
+*/
+static int completionOpen(sqlite3_vtab *p, sqlite3_vtab_cursor **ppCursor){
+ completion_cursor *pCur;
+ pCur = sqlite3_malloc( sizeof(*pCur) );
+ if( pCur==0 ) return SQLITE_NOMEM;
+ memset(pCur, 0, sizeof(*pCur));
+ pCur->db = ((completion_vtab*)p)->db;
+ *ppCursor = &pCur->base;
+ return SQLITE_OK;
+}
+
+/*
+** Reset the completion_cursor.
+*/
+static void completionCursorReset(completion_cursor *pCur){
+ sqlite3_free(pCur->zPrefix); pCur->zPrefix = 0; pCur->nPrefix = 0;
+ sqlite3_free(pCur->zLine); pCur->zLine = 0; pCur->nLine = 0;
+ sqlite3_finalize(pCur->pStmt); pCur->pStmt = 0;
+ pCur->j = 0;
+}
+
+/*
+** Destructor for a completion_cursor.
+*/
+static int completionClose(sqlite3_vtab_cursor *cur){
+ completionCursorReset((completion_cursor*)cur);
+ sqlite3_free(cur);
+ return SQLITE_OK;
+}
+
+/*
+** Advance a completion_cursor to its next row of output.
+**
+** The ->ePhase, ->j, and ->pStmt fields of the completion_cursor object
+** record the current state of the scan. This routine sets ->zCurrentRow
+** to the current row of output and then returns. If no more rows remain,
+** then ->ePhase is set to COMPLETION_EOF which will signal the virtual
+** table that has reached the end of its scan.
+**
+** The current implementation just lists potential identifiers and
+** keywords and filters them by zPrefix. Future enhancements should
+** take zLine into account to try to restrict the set of identifiers and
+** keywords based on what would be legal at the current point of input.
+*/
+static int completionNext(sqlite3_vtab_cursor *cur){
+ completion_cursor *pCur = (completion_cursor*)cur;
+ int eNextPhase = 0; /* Next phase to try if current phase reaches end */
+ int iCol = -1; /* If >=0, step pCur->pStmt and use the i-th column */
+ pCur->iRowid++;
+ while( pCur->ePhase!=COMPLETION_EOF ){
+ switch( pCur->ePhase ){
+ case COMPLETION_KEYWORDS: {
+ if( pCur->j >= sqlite3_keyword_count() ){
+ pCur->zCurrentRow = 0;
+ pCur->ePhase = COMPLETION_DATABASES;
+ }else{
+ sqlite3_keyword_name(pCur->j++, &pCur->zCurrentRow, &pCur->szRow);
+ }
+ iCol = -1;
+ break;
+ }
+ case COMPLETION_DATABASES: {
+ if( pCur->pStmt==0 ){
+ sqlite3_prepare_v2(pCur->db, "PRAGMA database_list", -1,
+ &pCur->pStmt, 0);
+ }
+ iCol = 1;
+ eNextPhase = COMPLETION_TABLES;
+ break;
+ }
+ case COMPLETION_TABLES: {
+ if( pCur->pStmt==0 ){
+ sqlite3_stmt *pS2;
+ char *zSql = 0;
+ const char *zSep = "";
+ sqlite3_prepare_v2(pCur->db, "PRAGMA database_list", -1, &pS2, 0);
+ while( sqlite3_step(pS2)==SQLITE_ROW ){
+ const char *zDb = (const char*)sqlite3_column_text(pS2, 1);
+ zSql = sqlite3_mprintf(
+ "%z%s"
+ "SELECT name FROM \"%w\".sqlite_schema",
+ zSql, zSep, zDb
+ );
+ if( zSql==0 ) return SQLITE_NOMEM;
+ zSep = " UNION ";
+ }
+ sqlite3_finalize(pS2);
+ sqlite3_prepare_v2(pCur->db, zSql, -1, &pCur->pStmt, 0);
+ sqlite3_free(zSql);
+ }
+ iCol = 0;
+ eNextPhase = COMPLETION_COLUMNS;
+ break;
+ }
+ case COMPLETION_COLUMNS: {
+ if( pCur->pStmt==0 ){
+ sqlite3_stmt *pS2;
+ char *zSql = 0;
+ const char *zSep = "";
+ sqlite3_prepare_v2(pCur->db, "PRAGMA database_list", -1, &pS2, 0);
+ while( sqlite3_step(pS2)==SQLITE_ROW ){
+ const char *zDb = (const char*)sqlite3_column_text(pS2, 1);
+ zSql = sqlite3_mprintf(
+ "%z%s"
+ "SELECT pti.name FROM \"%w\".sqlite_schema AS sm"
+ " JOIN pragma_table_info(sm.name,%Q) AS pti"
+ " WHERE sm.type='table'",
+ zSql, zSep, zDb, zDb
+ );
+ if( zSql==0 ) return SQLITE_NOMEM;
+ zSep = " UNION ";
+ }
+ sqlite3_finalize(pS2);
+ sqlite3_prepare_v2(pCur->db, zSql, -1, &pCur->pStmt, 0);
+ sqlite3_free(zSql);
+ }
+ iCol = 0;
+ eNextPhase = COMPLETION_EOF;
+ break;
+ }
+ }
+ if( iCol<0 ){
+ /* This case is when the phase presets zCurrentRow */
+ if( pCur->zCurrentRow==0 ) continue;
+ }else{
+ if( sqlite3_step(pCur->pStmt)==SQLITE_ROW ){
+ /* Extract the next row of content */
+ pCur->zCurrentRow = (const char*)sqlite3_column_text(pCur->pStmt, iCol);
+ pCur->szRow = sqlite3_column_bytes(pCur->pStmt, iCol);
+ }else{
+ /* When all rows are finished, advance to the next phase */
+ sqlite3_finalize(pCur->pStmt);
+ pCur->pStmt = 0;
+ pCur->ePhase = eNextPhase;
+ continue;
+ }
+ }
+ if( pCur->nPrefix==0 ) break;
+ if( pCur->nPrefix<=pCur->szRow
+ && sqlite3_strnicmp(pCur->zPrefix, pCur->zCurrentRow, pCur->nPrefix)==0
+ ){
+ break;
+ }
+ }
+
+ return SQLITE_OK;
+}
+
+/*
+** Return values of columns for the row at which the completion_cursor
+** is currently pointing.
+*/
+static int completionColumn(
+ sqlite3_vtab_cursor *cur, /* The cursor */
+ sqlite3_context *ctx, /* First argument to sqlite3_result_...() */
+ int i /* Which column to return */
+){
+ completion_cursor *pCur = (completion_cursor*)cur;
+ switch( i ){
+ case COMPLETION_COLUMN_CANDIDATE: {
+ sqlite3_result_text(ctx, pCur->zCurrentRow, pCur->szRow,SQLITE_TRANSIENT);
+ break;
+ }
+ case COMPLETION_COLUMN_PREFIX: {
+ sqlite3_result_text(ctx, pCur->zPrefix, -1, SQLITE_TRANSIENT);
+ break;
+ }
+ case COMPLETION_COLUMN_WHOLELINE: {
+ sqlite3_result_text(ctx, pCur->zLine, -1, SQLITE_TRANSIENT);
+ break;
+ }
+ case COMPLETION_COLUMN_PHASE: {
+ sqlite3_result_int(ctx, pCur->ePhase);
+ break;
+ }
+ }
+ return SQLITE_OK;
+}
+
+/*
+** Return the rowid for the current row. In this implementation, the
+** rowid is the same as the output value.
+*/
+static int completionRowid(sqlite3_vtab_cursor *cur, sqlite_int64 *pRowid){
+ completion_cursor *pCur = (completion_cursor*)cur;
+ *pRowid = pCur->iRowid;
+ return SQLITE_OK;
+}
+
+/*
+** Return TRUE if the cursor has been moved off of the last
+** row of output.
+*/
+static int completionEof(sqlite3_vtab_cursor *cur){
+ completion_cursor *pCur = (completion_cursor*)cur;
+ return pCur->ePhase >= COMPLETION_EOF;
+}
+
+/*
+** This method is called to "rewind" the completion_cursor object back
+** to the first row of output. This method is always called at least
+** once prior to any call to completionColumn() or completionRowid() or
+** completionEof().
+*/
+static int completionFilter(
+ sqlite3_vtab_cursor *pVtabCursor,
+ int idxNum, const char *idxStr,
+ int argc, sqlite3_value **argv
+){
+ completion_cursor *pCur = (completion_cursor *)pVtabCursor;
+ int iArg = 0;
+ (void)(idxStr); /* Unused parameter */
+ (void)(argc); /* Unused parameter */
+ completionCursorReset(pCur);
+ if( idxNum & 1 ){
+ pCur->nPrefix = sqlite3_value_bytes(argv[iArg]);
+ if( pCur->nPrefix>0 ){
+ pCur->zPrefix = sqlite3_mprintf("%s", sqlite3_value_text(argv[iArg]));
+ if( pCur->zPrefix==0 ) return SQLITE_NOMEM;
+ }
+ iArg = 1;
+ }
+ if( idxNum & 2 ){
+ pCur->nLine = sqlite3_value_bytes(argv[iArg]);
+ if( pCur->nLine>0 ){
+ pCur->zLine = sqlite3_mprintf("%s", sqlite3_value_text(argv[iArg]));
+ if( pCur->zLine==0 ) return SQLITE_NOMEM;
+ }
+ }
+ if( pCur->zLine!=0 && pCur->zPrefix==0 ){
+ int i = pCur->nLine;
+ while( i>0 && (isalnum(pCur->zLine[i-1]) || pCur->zLine[i-1]=='_') ){
+ i--;
+ }
+ pCur->nPrefix = pCur->nLine - i;
+ if( pCur->nPrefix>0 ){
+ pCur->zPrefix = sqlite3_mprintf("%.*s", pCur->nPrefix, pCur->zLine + i);
+ if( pCur->zPrefix==0 ) return SQLITE_NOMEM;
+ }
+ }
+ pCur->iRowid = 0;
+ pCur->ePhase = COMPLETION_FIRST_PHASE;
+ return completionNext(pVtabCursor);
+}
+
+/*
+** SQLite will invoke this method one or more times while planning a query
+** that uses the completion virtual table. This routine needs to create
+** a query plan for each invocation and compute an estimated cost for that
+** plan.
+**
+** There are two hidden parameters that act as arguments to the table-valued
+** function: "prefix" and "wholeline". Bit 0 of idxNum is set if "prefix"
+** is available and bit 1 is set if "wholeline" is available.
+*/
+static int completionBestIndex(
+ sqlite3_vtab *tab,
+ sqlite3_index_info *pIdxInfo
+){
+ int i; /* Loop over constraints */
+ int idxNum = 0; /* The query plan bitmask */
+ int prefixIdx = -1; /* Index of the start= constraint, or -1 if none */
+ int wholelineIdx = -1; /* Index of the stop= constraint, or -1 if none */
+ int nArg = 0; /* Number of arguments that completeFilter() expects */
+ const struct sqlite3_index_constraint *pConstraint;
+
+ (void)(tab); /* Unused parameter */
+ pConstraint = pIdxInfo->aConstraint;
+ for(i=0; i<pIdxInfo->nConstraint; i++, pConstraint++){
+ if( pConstraint->usable==0 ) continue;
+ if( pConstraint->op!=SQLITE_INDEX_CONSTRAINT_EQ ) continue;
+ switch( pConstraint->iColumn ){
+ case COMPLETION_COLUMN_PREFIX:
+ prefixIdx = i;
+ idxNum |= 1;
+ break;
+ case COMPLETION_COLUMN_WHOLELINE:
+ wholelineIdx = i;
+ idxNum |= 2;
+ break;
+ }
+ }
+ if( prefixIdx>=0 ){
+ pIdxInfo->aConstraintUsage[prefixIdx].argvIndex = ++nArg;
+ pIdxInfo->aConstraintUsage[prefixIdx].omit = 1;
+ }
+ if( wholelineIdx>=0 ){
+ pIdxInfo->aConstraintUsage[wholelineIdx].argvIndex = ++nArg;
+ pIdxInfo->aConstraintUsage[wholelineIdx].omit = 1;
+ }
+ pIdxInfo->idxNum = idxNum;
+ pIdxInfo->estimatedCost = (double)5000 - 1000*nArg;
+ pIdxInfo->estimatedRows = 500 - 100*nArg;
+ return SQLITE_OK;
+}
+
+/*
+** This following structure defines all the methods for the
+** completion virtual table.
+*/
+static sqlite3_module completionModule = {
+ 0, /* iVersion */
+ 0, /* xCreate */
+ completionConnect, /* xConnect */
+ completionBestIndex, /* xBestIndex */
+ completionDisconnect, /* xDisconnect */
+ 0, /* xDestroy */
+ completionOpen, /* xOpen - open a cursor */
+ completionClose, /* xClose - close a cursor */
+ completionFilter, /* xFilter - configure scan constraints */
+ completionNext, /* xNext - advance a cursor */
+ completionEof, /* xEof - check for end of scan */
+ completionColumn, /* xColumn - read data */
+ completionRowid, /* 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 */
+};
+
+#endif /* SQLITE_OMIT_VIRTUALTABLE */
+
+int sqlite3CompletionVtabInit(sqlite3 *db){
+ int rc = SQLITE_OK;
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+ rc = sqlite3_create_module(db, "completion", &completionModule, 0);
+#endif
+ return rc;
+}
+
+#ifdef _WIN32
+__declspec(dllexport)
+#endif
+int sqlite3_completion_init(
+ sqlite3 *db,
+ char **pzErrMsg,
+ const sqlite3_api_routines *pApi
+){
+ int rc = SQLITE_OK;
+ SQLITE_EXTENSION_INIT2(pApi);
+ (void)(pzErrMsg); /* Unused parameter */
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+ rc = sqlite3CompletionVtabInit(db);
+#endif
+ return rc;
+}
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