drop the SG library completely.

1 files changed, 0 insertions, 2408 deletions

diff --git a/src/runtime/c/sg/sg.c b/src/runtime/c/sg/sg.c
deleted file mode 100644
index b5a473b99..000000000
--- a/src/runtime/c/sg/sg.c
+++ /dev/null
@@ -1,2408 +0,0 @@
-#include <stdlib.h>
-#include "sqlite3Btree.h"
-
-#include "sg/sg.h"
-#include "gu/mem.h"
-#include "pgf/data.h"
-
-#define SG_EXPRS       1
-#define SG_PAIRS       2
-#define SG_IDENTS      3
-#define SG_LITERALS    4
-#define SG_TOKENS      5
-#define SG_TRIPLES     6
-#define SG_TRIPLES_SPO 7
-#define SG_TRIPLES_PO  8
-#define SG_TRIPLES_O   9
-
-struct SgSG {
-	Btree *pBtree;
-	int exprsTNum;                /* The page number for the table of expressions */
-	int identsTNum;               /* The page number for the index on identifiers */
-	int literalsTNum;             /* The page number for the index on literals */
-	int pairsTNum;                /* The page number for the index on application pairs */
-	int tokensTNum;               /* The page number for the index on linearization tokens */
-	int triplesTNum;              /* The page number for the table of triples */
-	int triplesIdxTNum[3];        /* The page number for the three indexes on triples */
-	int autoCommit;
-};
-
-void
-sg_raise_sqlite(int rc, GuExn* err)
-{
-	const char *msg = sqlite3BtreeErrName(rc);
-
-	GuExnData* err_data = gu_raise(err, SgError);
-	if (err_data) {
-		err_data->data = gu_malloc(err_data->pool, strlen(msg)+1);
-		strcpy(err_data->data, msg);
-	}
-}
-
-void
-sg_raise_err(GuString msg, GuExn* err)
-{
-	GuExnData* err_data = gu_raise(err, SgError);
-	if (err_data) {
-		err_data->data = (char*) msg;
-	}
-}
-
-static int
-sg_create_table(Btree* pBtree, BtCursor* crsSchema, int tblKey, int* pTNum, int flags)
-{
-	int rc;
-	int file_format = sqlite3BtreeFileFormat(pBtree);
-
-	int res = 0;
-	rc = sqlite3BtreeMovetoUnpacked(crsSchema, 0, tblKey, 0, &res);
-	if (rc != SQLITE_OK) {
-		return rc;
-	}
-
-	Mem mem;
-	int serial_type;
-
-	if (res == 0) {
-		u32 payloadSize;
-		rc = sqlite3BtreeDataSize(crsSchema, &payloadSize);
-		if (rc != SQLITE_OK)
-			return rc;
-
-		u32 avail = 0;
-		const unsigned char* row = sqlite3BtreeDataFetch(crsSchema, &avail);
-		row++;
-
-		row += getVarint32(row, serial_type);
-		row += sqlite3BtreeSerialGet(row, serial_type, &mem);
-		assert(mem.flags & MEM_Int);
-
-		*pTNum = mem.u.i;
-	} else {
-		rc = sqlite3BtreeCreateTable(pBtree, pTNum, flags);
-		if (rc != SQLITE_OK) {
-			return rc;
-		}
-
-		mem.flags = MEM_Int;
-		mem.u.i = *pTNum;
-
-		unsigned char buf[32];
-		unsigned char *p;
-
-        buf[0] = 2;
-		serial_type = sqlite3BtreeSerialType(&mem, file_format);
-		buf[1] = serial_type;
-		
-		p = buf+2;
-		p += sqlite3BtreeSerialPut(buf+2, &mem, serial_type);
-
-		rc = sqlite3BtreeInsert(crsSchema, 0, tblKey,
-			                        buf, p-buf, 0,
-			                        0, 0);
-		if (rc != SQLITE_OK)
-			return rc;		
-	}
-
-	return SQLITE_OK;
-}
-
-SgSG*
-sg_open(const char *filename,
-        GuExn* err)
-{
-	int rc;
-
-	Btree* pBtree;
-    rc = sqlite3BtreeOpen(0, filename, &pBtree,
-                          0, SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE | SQLITE_OPEN_MAIN_DB);
-	if (rc != SQLITE_OK) {
-		sg_raise_sqlite(rc, err);
-		return NULL;
-	}
-
-	rc = sqlite3BtreeBeginTrans(pBtree, 1);
-	if (rc != SQLITE_OK) {
-		sg_raise_sqlite(rc, err);
-		sqlite3BtreeClose(pBtree);
-		return NULL;
-	}
-
-	BtCursor* crsSchema = NULL;
-	rc = sqlite3BtreeCursor(pBtree, 1, 1, 0, 0, &crsSchema);
-	if (rc != SQLITE_OK) {
-		sg_raise_sqlite(rc, err);
-		sqlite3BtreeClose(pBtree);
-		return NULL;
-	}
-
-	SgSG* sg = malloc(sizeof(SgSG));
-	sg->pBtree = pBtree;
-	sg->autoCommit = 1;
-
-	rc = sg_create_table(pBtree, crsSchema, SG_EXPRS, &sg->exprsTNum, BTREE_INTKEY);
-	if (rc != SQLITE_OK)
-		goto fail;
-
-	rc = sg_create_table(pBtree, crsSchema, SG_IDENTS, &sg->identsTNum, 0);
-	if (rc != SQLITE_OK)
-		goto fail;
-
-	rc = sg_create_table(pBtree, crsSchema, SG_LITERALS, &sg->literalsTNum, 0);
-	if (rc != SQLITE_OK)
-		goto fail;
-
-	rc = sg_create_table(pBtree, crsSchema, SG_PAIRS, &sg->pairsTNum, 0);
-	if (rc != SQLITE_OK)
-		goto fail;
-
-	rc = sg_create_table(pBtree, crsSchema, SG_TOKENS, &sg->tokensTNum, 0);
-	if (rc != SQLITE_OK)
-		goto fail;
-
-	rc = sg_create_table(pBtree, crsSchema, SG_TRIPLES, &sg->triplesTNum, BTREE_INTKEY);
-	if (rc != SQLITE_OK)
-		goto fail;
-
-	rc = sg_create_table(pBtree, crsSchema, SG_TRIPLES_SPO, &sg->triplesIdxTNum[0], 0);
-	if (rc != SQLITE_OK)
-		goto fail;
-
-	rc = sg_create_table(pBtree, crsSchema, SG_TRIPLES_PO, &sg->triplesIdxTNum[1], 0);
-	if (rc != SQLITE_OK)
-		goto fail;
-
-	rc = sg_create_table(pBtree, crsSchema, SG_TRIPLES_O, &sg->triplesIdxTNum[2], 0);
-	if (rc != SQLITE_OK)
-		goto fail;
-
-	sqlite3BtreeCloseCursor(crsSchema);
-
-	rc = sqlite3BtreeCommit(pBtree);
-	if (rc != SQLITE_OK)
-		goto fail;
-
-	return sg;
-	
-fail:
-	sg_raise_sqlite(rc, err);
-	if (crsSchema != NULL)
-		sqlite3BtreeCloseCursor(crsSchema);
-	sqlite3BtreeRollback(sg->pBtree, SQLITE_ABORT_ROLLBACK, 0);
-	sqlite3BtreeClose(pBtree);
-	free(sg);
-	return NULL;
-}
-
-void
-sg_close(SgSG* sg, GuExn* err)
-{
-	sqlite3BtreeClose(sg->pBtree);
-}
-
-void
-sg_shutdown()
-{
-	sqlite3BtreeShutdown();
-}
-
-void
-sg_begin_trans(SgSG* sg, GuExn* err)
-{
-	int rc = sqlite3BtreeBeginTrans(sg->pBtree, 1);
-	if (rc != SQLITE_OK) {
-		sg_raise_sqlite(rc, err);
-		return;
-	}
-	sg->autoCommit = 0;
-}
-
-void
-sg_commit(SgSG* sg, GuExn* err)
-{
-	int rc = sqlite3BtreeCommit(sg->pBtree);
-	if (rc != SQLITE_OK) {
-		sg_raise_sqlite(rc, err);
-		return;
-	}
-	sg->autoCommit = 1;
-}
-
-void
-sg_rollback(SgSG* sg, GuExn* err)
-{
-	int rc = sqlite3BtreeRollback(sg->pBtree, SQLITE_ABORT_ROLLBACK, 0);
-	if (rc != SQLITE_OK) {
-		sg_raise_sqlite(rc, err);
-		return;
-	}
-	sg->autoCommit = 1;
-}
-
-typedef struct {
-	int n_cursors;
-	BtCursor* crsExprs;
-	BtCursor* crsIdents;
-	BtCursor* crsLiterals;
-	BtCursor* crsPairs;
-	SgId key_seed;
-} ExprContext;
-
-static int
-open_exprs(SgSG *sg, int wrFlag, bool identsOnly,
-           ExprContext* ctxt, GuExn* err)
-{
-	ctxt->n_cursors = 0;
-
-	int rc;
-
-	rc = sqlite3BtreeCursor(sg->pBtree, sg->exprsTNum, wrFlag, 0, 0, &ctxt->crsExprs);
-	if (rc != SQLITE_OK) {
-		sg_raise_sqlite(rc, err);
-		return rc;
-	}
-	ctxt->n_cursors++;
-
-	rc = sqlite3BtreeCursor(sg->pBtree, sg->identsTNum, wrFlag, 1, 1, &ctxt->crsIdents);
-	if (rc != SQLITE_OK) {
-		sg_raise_sqlite(rc, err);
-		return rc;
-	}
-	ctxt->n_cursors++;
-
-	if (!identsOnly) {
-		rc = sqlite3BtreeCursor(sg->pBtree, sg->literalsTNum, wrFlag, 1, 1, &ctxt->crsLiterals);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			return rc;
-		}
-		ctxt->n_cursors++;
-
-		rc = sqlite3BtreeCursor(sg->pBtree, sg->pairsTNum, wrFlag, 2, 0, &ctxt->crsPairs);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			return rc;
-		}
-		ctxt->n_cursors++;
-	}
-
-	if (wrFlag) {
-		int res;
-		rc = sqlite3BtreeLast(ctxt->crsExprs, &res);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			return rc;
-		}
-
-		rc = sqlite3BtreeKeySize(ctxt->crsExprs, &ctxt->key_seed);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			return rc;
-		}
-	} else {
-		ctxt->key_seed = 0;
-	}
-
-	return SQLITE_OK;
-}
-
-static void
-close_exprs(ExprContext* ctxt)
-{
-	if (ctxt->n_cursors >= 4) {
-		sqlite3BtreeCloseCursor(ctxt->crsPairs);
-	}
-
-	if (ctxt->n_cursors >= 3) {
-		sqlite3BtreeCloseCursor(ctxt->crsLiterals);
-	}
-
-	if (ctxt->n_cursors >= 2) {
-		sqlite3BtreeCloseCursor(ctxt->crsIdents);
-	}
-
-	if (ctxt->n_cursors >= 1) {
-		sqlite3BtreeCloseCursor(ctxt->crsExprs);
-	}
-	
-	ctxt->n_cursors = 0;
-}
-
-static int
-find_function_rowid(SgSG* sg, ExprContext* ctxt,
-                    GuString fun, SgId* pKey, int wrFlag)
-{
-	int rc = SQLITE_OK;
-	int file_format = sqlite3BtreeFileFormat(sg->pBtree);
-
-	Mem mem[2];
-	mem[0].flags = MEM_Str;
-	mem[0].n = strlen(fun);
-	mem[0].z = (void*) fun;
-
-	UnpackedRecord idxKey;
-	sqlite3BtreeInitUnpackedRecord(&idxKey, ctxt->crsIdents, 1, 0, mem);
-
-	int res = 0;
-	rc = sqlite3BtreeMovetoUnpacked(ctxt->crsIdents,
-									&idxKey, 0,  0, &res);
-	if (rc != SQLITE_OK) {
-		return rc;
-	}
-
-	if (res == 0) {
-		rc = sqlite3BtreeIdxRowid(sg->pBtree, ctxt->crsIdents, pKey);
-	} else {
-		if (wrFlag == 0) {
-			*pKey = 0;
-			return SQLITE_OK;
-		}
-
-		*pKey = ++ctxt->key_seed;
-
-		int serial_type_fun = sqlite3BtreeSerialType(&mem[0], file_format);
-		int serial_type_fun_hdr_len = sqlite3BtreeVarintLen(serial_type_fun);
-
-		mem[1].flags = MEM_Int;
-		mem[1].u.i = *pKey;
-
-		int serial_type_key = sqlite3BtreeSerialType(&mem[1], file_format);
-		int serial_type_key_hdr_len = sqlite3BtreeVarintLen(serial_type_key);
-
-		unsigned char* buf = malloc(1+serial_type_fun_hdr_len+(serial_type_key_hdr_len > 1 ? serial_type_key_hdr_len : 1)+mem[0].n+8);
-		unsigned char* p = buf;
-		*p++ = 1+serial_type_fun_hdr_len+1;
-		p += putVarint32(p, serial_type_fun);
-		*p++ = 0;
-		memcpy(p, fun, mem[0].n);
-		p += mem[0].n;
-
-		rc = sqlite3BtreeInsert(ctxt->crsExprs, 0, *pKey,
-		                        buf, p-buf, 0,
-		                        0, 0);
-		if (rc != SQLITE_OK) {
-			goto free;
-		}
-
-		p = buf;
-		*p++ = 1+serial_type_fun_hdr_len+serial_type_key_hdr_len;
-		p += putVarint32(p, serial_type_fun);
-		p += putVarint32(p, serial_type_key);
-		memcpy(p, fun, mem[0].n);
-		p += mem[0].n;
-		p += sqlite3BtreeSerialPut(p, &mem[1], serial_type_key);
-		rc = sqlite3BtreeInsert(ctxt->crsIdents, buf, p-buf,
-		                        0, *pKey, 0,
-		                        0, 0);
-
-free:
-		free(buf);
-	}
-
-	return rc;
-}
-
-static int
-store_expr(SgSG* sg,
-           ExprContext* ctxt, PgfExpr expr, SgId* pKey, int wrFlag)
-{
-	int rc = SQLITE_OK;
-	int file_format = sqlite3BtreeFileFormat(sg->pBtree);
-
-	GuVariantInfo ei = gu_variant_open(expr);
-	switch (ei.tag) {
-	case PGF_EXPR_ABS: {
-		gu_impossible();
-		break;
-	}
-	case PGF_EXPR_APP: {
-		PgfExprApp* app = ei.data;
-
-		Mem mem[3];
-
-		mem[0].flags = MEM_Int;
-		rc = store_expr(sg, ctxt, app->fun, &mem[0].u.i, wrFlag);
-		if (rc != SQLITE_OK)
-			return rc;
-		if (wrFlag == 0 && mem[0].u.i == 0) {
-			*pKey = 0;
-			return SQLITE_OK;
-		}
-
-		mem[1].flags = MEM_Int;
-		rc = store_expr(sg, ctxt, app->arg, &mem[1].u.i, wrFlag);
-		if (rc != SQLITE_OK)
-			return rc;
-		if (wrFlag == 0 && mem[1].u.i == 0) {
-			*pKey = 0;
-			return SQLITE_OK;
-		}
-
-		UnpackedRecord idxKey;
-		sqlite3BtreeInitUnpackedRecord(&idxKey, ctxt->crsPairs, 2, 0, mem);
-
-		int res = 0;
-		rc = sqlite3BtreeMovetoUnpacked(ctxt->crsPairs,
-		                                &idxKey, 0,  0, &res);
-		if (rc != SQLITE_OK) {
-			return rc;
-		}
-
-		if (res == 0) {
-			rc = sqlite3BtreeIdxRowid(sg->pBtree, ctxt->crsPairs, pKey);
-		} else {
-			if (wrFlag == 0) {
-				*pKey = 0;
-				return SQLITE_OK;
-			}
-
-			*pKey = ++ctxt->key_seed;
-
-			unsigned char buf[32];  // enough for a record with three integers
-			buf[1] = 3;
-
-			u32 serial_type;
-			unsigned char* p = buf+4;
-
-			serial_type = sqlite3BtreeSerialType(&mem[0], file_format);
-			buf[2] = serial_type;
-			p += sqlite3BtreeSerialPut(p, &mem[0], serial_type);
-
-			serial_type = sqlite3BtreeSerialType(&mem[1], file_format);
-			buf[3] = serial_type;
-			p += sqlite3BtreeSerialPut(p, &mem[1], serial_type);
-
-			rc = sqlite3BtreeInsert(ctxt->crsExprs, 0, *pKey,
-			                        buf+1, p-(buf+1), 0,
-			                        0, 0);
-			if (rc != SQLITE_OK) {
-				return rc;
-			}
-
-			buf[0] = 4;
-			buf[1] = buf[2];
-			buf[2] = buf[3];
-
-			mem[2].flags = MEM_Int;
-			mem[2].u.i = *pKey;
-			serial_type = sqlite3BtreeSerialType(&mem[2], file_format);
-			buf[3] = serial_type;
-			p += sqlite3BtreeSerialPut(p, &mem[2], serial_type);
-
-			rc = sqlite3BtreeInsert(ctxt->crsPairs, buf, p-buf,
-			                        0, *pKey, 0,
-			                        0, 0);
-        }
-		break;
-	}
-	case PGF_EXPR_LIT: {
-		PgfExprLit* elit = ei.data;
-
-		Mem mem[2];
-		size_t len = 0;
-
-		GuVariantInfo li = gu_variant_open(elit->lit);
-		switch (li.tag) {
-		case PGF_LITERAL_STR: {
-			PgfLiteralStr* lstr = li.data;
-
-			len = strlen(lstr->val);
-
-			mem[0].flags = MEM_Str;
-			mem[0].n = len;
-			mem[0].z = lstr->val;
-			break;
-		}
-		case PGF_LITERAL_INT: {
-			PgfLiteralInt* lint = li.data;
-
-			mem[0].flags = MEM_Int;
-			mem[0].u.i = lint->val;
-			len = sizeof(mem[0].u.i);
-			break;
-		}
-		case PGF_LITERAL_FLT: {
-			PgfLiteralFlt* lflt = li.data;
-
-			mem[0].flags = MEM_Real;
-			mem[0].u.r = lflt->val;
-			len = sizeof(mem[0].u.r);
-			break;
-		}
-		default:
-			gu_impossible();
-		}
-
-		UnpackedRecord idxKey;
-		sqlite3BtreeInitUnpackedRecord(&idxKey, ctxt->crsIdents, 1, 0, mem);
-
-		int res = 0;
-		rc = sqlite3BtreeMovetoUnpacked(ctxt->crsLiterals,
-		                                &idxKey, 0,  0, &res);
-		if (rc != SQLITE_OK) {
-			return rc;
-		}
-
-		if (res == 0) {
-			rc = sqlite3BtreeIdxRowid(sg->pBtree, ctxt->crsLiterals, pKey);
-		} else {
-			if (wrFlag == 0) {
-				*pKey = 0;
-				return SQLITE_OK;
-			}
-
-			*pKey = ++ctxt->key_seed;
-
-			mem[1].flags = MEM_Int;
-			mem[1].u.i = 0;
-
-			int serial_type_lit = sqlite3BtreeSerialType(&mem[0], file_format);
-			int serial_type_lit_hdr_len = sqlite3BtreeVarintLen(serial_type_lit);
-			int serial_type_arg = sqlite3BtreeSerialType(&mem[1], file_format);
-			int serial_type_arg_hdr_len = sqlite3BtreeVarintLen(serial_type_arg);
-
-			unsigned char* buf = malloc(1+serial_type_lit_hdr_len+(serial_type_arg_hdr_len > 1 ? serial_type_arg_hdr_len : 1)+len+8);
-			unsigned char* p = buf;
-			*p++ = 1+serial_type_lit_hdr_len+serial_type_arg_hdr_len;
-			p += putVarint32(p, serial_type_lit);
-			p += putVarint32(p, serial_type_arg);
-			p += sqlite3BtreeSerialPut(p, &mem[0], serial_type_lit);
-			p += sqlite3BtreeSerialPut(p, &mem[1], serial_type_arg);
-
-			rc = sqlite3BtreeInsert(ctxt->crsExprs, 0, *pKey,
-			                        buf, p-buf, 0,
-			                        0, 0);
-			if (rc == SQLITE_OK) {
-				mem[1].flags = MEM_Int;
-				mem[1].u.i = *pKey;
-
-				int serial_type_key = sqlite3BtreeSerialType(&mem[1], file_format);
-				int serial_type_key_hdr_len = sqlite3BtreeVarintLen(serial_type_key);
-
-				p = buf;
-				*p++ = 1+serial_type_lit_hdr_len+serial_type_key_hdr_len;
-				p += putVarint32(p, serial_type_lit);
-				p += putVarint32(p, serial_type_key);
-				p += sqlite3BtreeSerialPut(p, &mem[0], serial_type_lit);
-				p += sqlite3BtreeSerialPut(p, &mem[1], serial_type_key);
-				rc = sqlite3BtreeInsert(ctxt->crsLiterals, buf, p-buf,
-										0, *pKey, 0,
-										0, 0);
-			}
-
-			free(buf);
-		}
-		break;
-	}
-	case PGF_EXPR_META: {
-		gu_impossible();
-	}
-	case PGF_EXPR_FUN: {
-		PgfExprFun* fun = ei.data;
-		rc = find_function_rowid(sg, ctxt, fun->fun, pKey, wrFlag);
-        break;
-	}
-	case PGF_EXPR_VAR: {
-		gu_impossible();
-		break;
-	}
-	case PGF_EXPR_TYPED: {
-		PgfExprTyped* etyped = ei.data;
-		rc = store_expr(sg, ctxt, etyped->expr, pKey, wrFlag);
-		break;
-	}
-	case PGF_EXPR_IMPL_ARG: {
-		PgfExprImplArg* eimpl = ei.data;
-		rc = store_expr(sg, ctxt, eimpl->expr, pKey, wrFlag);
-		break;
-	}
-	default:
-		gu_impossible();
-	}
-
-	return rc;
-}
-
-SgId
-sg_insert_expr(SgSG *sg, PgfExpr expr, int wrFlag, GuExn* err)
-{
-	int rc;
-
-	if (sg->autoCommit) {
-		rc = sqlite3BtreeBeginTrans(sg->pBtree, wrFlag);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			return 0;
-		}
-	}
-
-	ExprContext ctxt;
-	rc = open_exprs(sg, wrFlag, false, &ctxt, err);
-	if (rc != SQLITE_OK)
-		goto close;
-
-	SgId key;
-	rc = store_expr(sg, &ctxt, expr, &key, wrFlag);
-	if (rc != SQLITE_OK) {
-		sg_raise_sqlite(rc, err);
-		goto close;
-	}
-
-	close_exprs(&ctxt);
-
-	if (sg->autoCommit) {
-		rc = sqlite3BtreeCommit(sg->pBtree);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			return 0;
-		}
-	}
-
-    return key;
-
-close:
-	close_exprs(&ctxt);
-
-	if (sg->autoCommit) {
-		sqlite3BtreeRollback(sg->pBtree, SQLITE_ABORT_ROLLBACK, 0);
-	}
-	return 0;
-}
-
-static int
-load_expr(BtCursor* crsExprs, SgId key, PgfExpr *pExpr, GuPool* out_pool)
-{
-	int res;
-	int rc = sqlite3BtreeMovetoUnpacked(crsExprs, 0, key, 0, &res);
-	if (rc != SQLITE_OK)
-		return rc;
-
-	if (res != 0) {
-		*pExpr = gu_null_variant;
-		return SQLITE_OK;
-	}
-
-	u32 payloadSize;
-	rc = sqlite3BtreeDataSize(crsExprs, &payloadSize);
-	if (rc != SQLITE_OK)
-		return rc;
-
-	u32 avail = 0;
-	const unsigned char* row = sqlite3BtreeDataFetch(crsExprs, &avail);
-	row++;
-
-	int serial_type_fun, serial_type_arg;
-	row += getVarint32(row, serial_type_fun);
-	row += getVarint32(row, serial_type_arg);
-
-	Mem mem[2];
-	row += sqlite3BtreeSerialGet(row, serial_type_fun, &mem[0]);
-	row += sqlite3BtreeSerialGet(row, serial_type_arg, &mem[1]);
-
-	if (mem[1].flags & MEM_Null) {
-		u32 len = sqlite3BtreeSerialTypeLen(serial_type_fun);
-
-		PgfExprFun *efun =
-			gu_new_flex_variant(PGF_EXPR_FUN,
-			                    PgfExprFun,
-			                    fun, len+1,
-			                    pExpr, out_pool);
-		memcpy(efun->fun, mem[0].z, len);
-		efun->fun[len] = 0;
-	} else if (mem[1].u.i == 0) {
-		PgfExprLit *elit =
-			gu_new_variant(PGF_EXPR_LIT,
-			               PgfExprLit,
-			               pExpr, out_pool);
-
-		if (mem[0].flags & MEM_Str) {
-			u32 len = sqlite3BtreeSerialTypeLen(serial_type_fun);
-
-			PgfLiteralStr *lstr =
-				gu_new_flex_variant(PGF_LITERAL_STR,
-				                    PgfLiteralStr,
-				                    val, len+1,
-				                    &elit->lit, out_pool);
-			memcpy(lstr->val, mem[0].z, len);
-			lstr->val[len] = 0;
-		} else if (mem[0].flags & MEM_Int) {
-			PgfLiteralInt *lint =
-				gu_new_variant(PGF_LITERAL_INT,
-				               PgfLiteralInt,
-				               &elit->lit, out_pool);
-			lint->val = mem[0].u.i;
-		} else if (mem[0].flags & MEM_Real) {
-			PgfLiteralFlt *lflt =
-				gu_new_variant(PGF_LITERAL_FLT,
-				               PgfLiteralFlt,
-				               &elit->lit, out_pool);
-			lflt->val = mem[0].u.r;
-		} else {
-			gu_impossible();
-		}
-	} else {
-		PgfExprApp* papp =
-			gu_new_variant(PGF_EXPR_APP, PgfExprApp, pExpr, out_pool);
-
-		rc = load_expr(crsExprs, mem[0].u.i, &papp->fun, out_pool);
-		if (rc != SQLITE_OK)
-			return rc;
-
-		rc = load_expr(crsExprs, mem[1].u.i, &papp->arg, out_pool);
-		if (rc != SQLITE_OK)
-			return rc;
-	}
-
-	return SQLITE_OK;
-}
-
-PgfExpr
-sg_get_expr(SgSG *sg, SgId key, GuPool* out_pool, GuExn* err)
-{
-	int rc;
-	if (sg->autoCommit) {
-		rc = sqlite3BtreeBeginTrans(sg->pBtree, 0);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			return gu_null_variant;
-		}
-	}
-
-	BtCursor* crsExprs;
-	rc = sqlite3BtreeCursor(sg->pBtree, sg->exprsTNum, 0, 0, 0, &crsExprs);
-	if (rc != SQLITE_OK) {
-		sg_raise_sqlite(rc, err);
-		goto rollback;
-	}
-
-	PgfExpr expr = gu_null_variant;
-	rc = load_expr(crsExprs, key, &expr, out_pool);
-	if (rc != SQLITE_OK) {
-		sg_raise_sqlite(rc, err);
-		goto close;
-	}
-
-	rc = sqlite3BtreeCloseCursor(crsExprs);
-	if (rc != SQLITE_OK) {
-		sg_raise_sqlite(rc, err);
-		goto rollback;
-	}
-
-	if (sg->autoCommit) {
-		rc = sqlite3BtreeCommit(sg->pBtree);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			goto rollback;
-		}
-	}
-
-    return expr;
-
-close:
-	sqlite3BtreeCloseCursor(crsExprs);
-
-rollback:
-	if (sg->autoCommit) {
-		sqlite3BtreeRollback(sg->pBtree, SQLITE_ABORT_ROLLBACK, 0);
-	}
-	return gu_null_variant;
-}
-
-// A query is compiled into a sequence of instructions with
-// the following codes:
-#define QI_PUSH   1
-#define QI_VAR    2
-#define QI_APPLY  3
-#define QI_RETURN 4
-
-typedef struct {
-	int  code;
-	SgId arg;
-} QueryInstr;
-
-struct SgQueryExprResult {
-	ExprContext ectxt;
-	GuBuf* instrs;
-	GuBuf* queue;
-	size_t iState;
-	PgfMetaId min_meta_id;
-	PgfMetaId max_meta_id;
-};
-
-typedef struct QueryArg QueryArg;
-struct QueryArg {
-	QueryArg* prev;
-	SgId arg;
-};
-
-typedef struct {
-	QueryArg* args;  // a stack of arguments
-	int pc;          // program counter
-} QueryState;
-
-static int
-build_expr_query(SgSG* sg,
-                 SgQueryExprResult* ctxt, PgfExpr expr)
-{
-	int rc = SQLITE_OK;
-
-	GuVariantInfo ei = gu_variant_open(expr);
-	switch (ei.tag) {
-	case PGF_EXPR_ABS: {
-		gu_impossible();
-		break;
-	}
-	case PGF_EXPR_APP: {
-		PgfExprApp* app = ei.data;
-
-		rc = build_expr_query(sg, ctxt, app->fun);
-		if (rc != SQLITE_OK)
-			return rc;
-		QueryInstr* first =
-			gu_buf_index_last(ctxt->instrs, QueryInstr);
-
-		rc = build_expr_query(sg, ctxt, app->arg);
-		if (rc != SQLITE_OK)
-			return rc;
-		QueryInstr* second =
-			gu_buf_index_last(ctxt->instrs, QueryInstr);
-
-		if (first->code == QI_PUSH && second->code == QI_PUSH &&
-		    second - first == 1) {
-			// we could directly combine the two expressions
-
-			Mem mem[2];
-			mem[0].flags = MEM_Int;
-			mem[0].u.i   = first->arg;
-			mem[1].flags = MEM_Int;
-			mem[1].u.i   = second->arg;
-
-			UnpackedRecord idxKey;
-			sqlite3BtreeInitUnpackedRecord(&idxKey, ctxt->ectxt.crsPairs, 2, 0, mem);
-
-			int res = 0;
-			rc = sqlite3BtreeMovetoUnpacked(ctxt->ectxt.crsPairs,
-											&idxKey, 0,  0, &res);
-			if (rc != SQLITE_OK)
-				return rc;
-			if (res != 0)
-				return SQLITE_DONE;
-
-			gu_buf_pop(ctxt->instrs, QueryInstr);
-
-			rc = sqlite3BtreeIdxRowid(sg->pBtree, ctxt->ectxt.crsPairs, &first->arg);
-   		} else if (gu_variant_tag(app->arg) != PGF_EXPR_META) {
-			QueryInstr* instr = gu_buf_extend(ctxt->instrs);
-			instr->code = QI_APPLY;
-			instr->arg  = 0;
-		}
-		break;
-	}
-	case PGF_EXPR_LIT: {
-		PgfExprLit* elit = ei.data;
-
-		Mem mem;
-
-		GuVariantInfo li = gu_variant_open(elit->lit);
-		switch (li.tag) {
-		case PGF_LITERAL_STR: {
-			PgfLiteralStr* lstr = li.data;
-
-			mem.flags = MEM_Str;
-			mem.n = strlen(lstr->val);
-			mem.z = lstr->val;
-			break;
-		}
-		case PGF_LITERAL_INT: {
-			PgfLiteralInt* lint = li.data;
-
-			mem.flags = MEM_Int;
-			mem.u.i = lint->val;
-			break;
-		}
-		case PGF_LITERAL_FLT: {
-			PgfLiteralFlt* lflt = li.data;
-
-			mem.flags = MEM_Real;
-			mem.u.r = lflt->val;
-			break;
-		}
-		default:
-			gu_impossible();
-		}
-
-		UnpackedRecord idxKey;
-		sqlite3BtreeInitUnpackedRecord(&idxKey, ctxt->ectxt.crsIdents, 1, 0, &mem);
-
-		int res = 0;
-		rc = sqlite3BtreeMovetoUnpacked(ctxt->ectxt.crsLiterals,
-		                                &idxKey, 0,  0, &res);
-		if (rc != SQLITE_OK)
-			return rc;
-		if (res != 0)
-			return SQLITE_DONE;
-
-		QueryInstr* instr = gu_buf_extend(ctxt->instrs);
-		instr->code = QI_PUSH;
-		rc = sqlite3BtreeIdxRowid(sg->pBtree, ctxt->ectxt.crsLiterals, &instr->arg);
-		break;
-	}
-	case PGF_EXPR_META: {
-		PgfExprMeta* emeta = ei.data;
-		QueryInstr* instr = gu_buf_extend(ctxt->instrs);
-		instr->code = QI_VAR;
-		instr->arg  = emeta->id;
-		
-		if (ctxt->min_meta_id > emeta->id)
-			ctxt->min_meta_id = emeta->id;
-		if (ctxt->max_meta_id < emeta->id)
-			ctxt->max_meta_id = emeta->id;
-		break;
-	}
-	case PGF_EXPR_FUN: {
-		PgfExprFun* fun = ei.data;
-
-		QueryInstr* instr = gu_buf_extend(ctxt->instrs);
-		instr->code = QI_PUSH;
-		rc = find_function_rowid(sg, &ctxt->ectxt, fun->fun, &instr->arg, 0);
-		if (rc == SQLITE_OK && instr->arg == 0)
-			return SQLITE_DONE;
-        break;
-	}
-	case PGF_EXPR_VAR: {
-		gu_impossible();
-		break;
-	}
-	case PGF_EXPR_TYPED: {
-		PgfExprTyped* etyped = ei.data;
-		rc = build_expr_query(sg, ctxt, etyped->expr);
-		break;
-	}
-	case PGF_EXPR_IMPL_ARG: {
-		PgfExprImplArg* eimpl = ei.data;
-		rc = build_expr_query(sg, ctxt, eimpl->expr);
-		break;
-	}
-	default:
-		gu_impossible();
-	}
-
-	return rc;
-}
-
-static int
-run_expr_query(SgSG* sg, SgQueryExprResult* ctxt, GuPool* pool)
-{
-	int rc;
-
-	while (ctxt->iState < gu_buf_length(ctxt->queue)) {
-		QueryState* state =
-			gu_buf_index(ctxt->queue, QueryState, ctxt->iState);
-		QueryInstr* instr =
-			gu_buf_index(ctxt->instrs, QueryInstr, state->pc);
-
-		switch (instr->code) {
-		case QI_PUSH: {
-			QueryArg* arg = gu_new(QueryArg, pool);
-			arg->arg  = instr->arg;
-			arg->prev = state->args;
-			state->args = arg;
-			break;
-		}
-		case QI_VAR: {
-			assert(state->args != NULL);
-
-			Mem mem;
-			mem.flags = MEM_Int;
-			mem.u.i   = state->args->arg;
-
-			UnpackedRecord idxKey;
-			sqlite3BtreeInitUnpackedRecord(&idxKey, ctxt->ectxt.crsPairs, 1, 1, &mem);
-
-			int res = 0;
-			rc = sqlite3BtreeMovetoUnpacked(ctxt->ectxt.crsPairs,
-											&idxKey, 0,  0, &res);
-			if (rc != SQLITE_OK)
-				return rc;
-			if (res < 0) {
-				rc = sqlite3BtreeNext(ctxt->ectxt.crsPairs, &res);
-			}
-			res = 0;
-
-			while (res == 0) {
-				i64 szData;
-				const unsigned char *zData;
-				rc = sqlite3BtreeKeySize(ctxt->ectxt.crsPairs, &szData);
-				if (rc != SQLITE_OK)
-					return rc;
-
-				u32 available = 0;
-				zData = sqlite3BtreeKeyFetch(ctxt->ectxt.crsPairs, &available);
-				if (szData > available)
-					gu_impossible();
-
-				idxKey.default_rc = 0;
-				res = sqlite3BtreeRecordCompare(available, zData, &idxKey);
-				if (res != 0)
-					break;
-
-				QueryArg* arg = gu_new(QueryArg, pool);
-				arg->prev = state->args->prev;
-
-				QueryState* state1 = gu_buf_extend(ctxt->queue);
-				state1->args = arg;
-				state1->pc   = state->pc+1;
-
-				rc = sqlite3BtreeIdxRowid(sg->pBtree, ctxt->ectxt.crsPairs, &arg->arg);
-				if (rc != SQLITE_OK)
-					return rc;
-
-				sqlite3BtreeNext(ctxt->ectxt.crsPairs, &res);
-				if (rc != SQLITE_OK)
-					return rc;
-			}
-
-			ctxt->iState++;
-			break;
-		}
-		case QI_APPLY: {
-			assert(state->args != NULL && state->args->prev);
-
-			Mem mem[2];
-			mem[0].flags = MEM_Int;
-			mem[0].u.i   = state->args->prev->arg;
-			mem[1].flags = MEM_Int;
-			mem[1].u.i   = state->args->arg;
-
-			UnpackedRecord idxKey;
-			sqlite3BtreeInitUnpackedRecord(&idxKey, ctxt->ectxt.crsPairs, 2, 0, mem);
-
-			int res = 0;
-			rc = sqlite3BtreeMovetoUnpacked(ctxt->ectxt.crsPairs,
-											&idxKey, 0,  0, &res);
-			if (rc != SQLITE_OK)
-				return rc;
-			if (res != 0) {
-				ctxt->iState++;
-				continue;
-			}
-
-			state->args = state->args->prev;
-
-			rc = sqlite3BtreeIdxRowid(sg->pBtree, ctxt->ectxt.crsPairs, &state->args->arg);
-			if (rc != SQLITE_OK)
-				return rc;
-			break;
-		}
-		case QI_RETURN:
-			return SQLITE_OK;
-		}
-
-		state->pc++;
-	}
-
-	return SQLITE_DONE;
-}
-
-SgQueryExprResult*
-sg_query_expr(SgSG *sg, PgfExpr expr, GuPool* pool, GuExn* err)
-{
-	int rc;
-
-	if (sg->autoCommit) {
-		rc = sqlite3BtreeBeginTrans(sg->pBtree, 0);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			return NULL;
-		}
-	}
-
-	SgQueryExprResult* ctxt = gu_new(SgQueryExprResult, pool);
-	rc = open_exprs(sg, 0, false, &ctxt->ectxt, err);
-	if (rc != SQLITE_OK)
-		goto close;
-
-	ctxt->instrs = gu_new_buf(QueryInstr, pool);
-	ctxt->queue  = gu_new_buf(QueryState, pool);
-	ctxt->iState = 0;
-	ctxt->min_meta_id = INT_MAX;
-	ctxt->max_meta_id = INT_MIN;
-
-	rc = build_expr_query(sg, ctxt, expr);
-	if (rc == SQLITE_OK) {
-		QueryInstr* instr = gu_buf_extend(ctxt->instrs);
-		instr->code = QI_RETURN;
-		instr->arg  = 0;
-
-		QueryState* state = gu_buf_extend(ctxt->queue);
-		state->args = NULL;
-		state->pc   = 0;
-	} else if (rc != SQLITE_DONE) {
-		sg_raise_sqlite(rc, err);
-		goto close;
-	}
-
-    return ctxt;
-
-close:
-	close_exprs(&ctxt->ectxt);
-
-	if (sg->autoCommit) {
-		sqlite3BtreeRollback(sg->pBtree, SQLITE_ABORT_ROLLBACK, 0);
-	}
-	return NULL;
-}
-
-PgfExpr
-sg_query_next(SgSG *sg, SgQueryExprResult* ctxt, SgId* pKey, GuPool* pool, GuExn* err)
-{
-	int rc;
-
-	rc = run_expr_query(sg, ctxt, pool);
-	if (rc == SQLITE_DONE)
-		return gu_null_variant;
-	if (rc != SQLITE_OK) {
-		sg_raise_sqlite(rc, err);
-		return gu_null_variant;
-	}
-
-	QueryState* state =
-		gu_buf_index(ctxt->queue, QueryState, ctxt->iState);
-	assert(state->args != NULL);
-	ctxt->iState++;
-
-	PgfExpr expr;
-	rc = load_expr(ctxt->ectxt.crsExprs, state->args->arg, &expr, pool);
-	if (rc != SQLITE_OK) {
-		sg_raise_sqlite(rc, err);
-		return gu_null_variant;
-	}
-
-	*pKey = state->args->arg;
-
-	return expr;
-}
-
-void
-sg_query_close(SgSG* sg, SgQueryExprResult* ctxt, GuExn* err)
-{
-	int rc;
-
-	close_exprs(&ctxt->ectxt);
-
-	if (sg->autoCommit) {
-		rc = sqlite3BtreeCommit(sg->pBtree);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-		}
-	}
-}
-
-static int
-insert_token(SgSG *sg, BtCursor* crsTokens, GuString tok, SgId key)
-{
-	int rc = SQLITE_OK;
-	int file_format = sqlite3BtreeFileFormat(sg->pBtree);
-
-	Mem mem[2];
-	mem[0].flags = MEM_Str;
-	mem[0].n = strlen(tok);
-	mem[0].z = (void*) tok;
-
-	int serial_type_tok = sqlite3BtreeSerialType(&mem[0], file_format);
-	int serial_type_tok_hdr_len = sqlite3BtreeVarintLen(serial_type_tok);
-
-	mem[1].flags = MEM_Int;
-	mem[1].u.i = key;
-
-	int serial_type_key = sqlite3BtreeSerialType(&mem[1], file_format);
-	int serial_type_key_hdr_len = sqlite3BtreeVarintLen(serial_type_key);
-
-	unsigned char* buf = malloc(1+serial_type_tok_hdr_len+serial_type_key_hdr_len+mem[0].n+8);
-	unsigned char* p = buf;
-	*p++ = 1+serial_type_tok_hdr_len+serial_type_key_hdr_len;
-	p += putVarint32(p, serial_type_tok);
-	p += putVarint32(p, serial_type_key);
-	memcpy(p, tok, mem[0].n);
-	p += mem[0].n;
-	p += sqlite3BtreeSerialPut(p, &mem[1], serial_type_key);
-	rc = sqlite3BtreeInsert(crsTokens, buf, p-buf,
-	                        0, key, 0,
-	                        0, 0);
-	free(buf);
-
-	return rc;
-}
-
-static int
-insert_syms(SgSG *sg, BtCursor* crsTokens, PgfSymbols* syms, SgId key)
-{
-	int rc;
-	size_t n_syms = gu_seq_length(syms);
-	for (size_t sym_idx = 0; sym_idx < n_syms; sym_idx++) {
-		PgfSymbol sym = gu_seq_get(syms, PgfSymbol, sym_idx);
-		GuVariantInfo sym_i = gu_variant_open(sym);
-		switch (sym_i.tag) {
-		case PGF_SYMBOL_KS: {
-			PgfSymbolKS* ks = sym_i.data;
-			rc = insert_token(sg, crsTokens, ks->token, key);
-			if (rc != SQLITE_OK)
-				return rc;
-			break;
-		}
-		case PGF_SYMBOL_KP: {
-			PgfSymbolKP* kp = sym_i.data;
-			rc = insert_syms(sg, crsTokens, kp->default_form, key);
-			if (rc != SQLITE_OK)
-				return rc;
-				
-			for (size_t i = 0; i < kp->n_forms; i++) {
-				rc = insert_syms(sg, crsTokens, kp->forms[i].form, key);
-				if (rc != SQLITE_OK)
-					return rc;
-			}
-			break;
-		}
-		}
-	}
-	
-	return SQLITE_OK;
-}
-
-void
-sg_update_fts_index(SgSG* sg, PgfPGF* pgf, GuExn* err)
-{
-	int rc = SQLITE_OK;
-
-	if (sg->autoCommit) {
-		rc = sqlite3BtreeBeginTrans(sg->pBtree, 1);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			return;
-		}
-	}
-
-	ExprContext ctxt;
-	rc = open_exprs(sg, 1, true, &ctxt, err);
-	if (rc != SQLITE_OK) {
-		sg_raise_sqlite(rc, err);
-		goto close;
-	}
-	
-	rc = sqlite3BtreeClearTable(sg->pBtree, sg->tokensTNum, NULL);
-	if (rc != SQLITE_OK) {
-		sg_raise_sqlite(rc, err);
-		return;
-	}
-
-	BtCursor* crsTokens;
-	rc = sqlite3BtreeCursor(sg->pBtree, sg->tokensTNum, 1, 1, 1, &crsTokens);
-	if (rc != SQLITE_OK) {
-		sg_raise_sqlite(rc, err);
-	}
-	ctxt.n_cursors++;
-
-	size_t n_concrs = gu_seq_length(pgf->concretes);
-	for (size_t i = 0; i < n_concrs; i++) {
-		PgfConcr* concr = gu_seq_index(pgf->concretes, PgfConcr, i);
-		
-		size_t n_funs = gu_seq_length(concr->cncfuns);
-		for (size_t funid = 0; funid < n_funs; funid++) {
-			PgfCncFun* cncfun = gu_seq_get(concr->cncfuns, PgfCncFun*, funid);
-
-			SgId key = 0;
-			rc = find_function_rowid(sg, &ctxt, cncfun->absfun->name, &key, 1);
-			if (rc != SQLITE_OK) {
-				sg_raise_sqlite(rc, err);
-				goto close;
-			}
-
-			for (size_t lin_idx = 0; lin_idx < cncfun->n_lins; lin_idx++) {
-				PgfSequence* seq = cncfun->lins[lin_idx];
-				rc = insert_syms(sg, crsTokens, seq->syms, key);
-				if (rc != SQLITE_OK) {
-					sg_raise_sqlite(rc, err);
-					goto close;
-				}
-			}
-		}
-	}
-
-	if (ctxt.n_cursors >= 3) {
-		sqlite3BtreeCloseCursor(crsTokens);
-		ctxt.n_cursors--;
-	}
-
-	close_exprs(&ctxt);
-	
-	if (sg->autoCommit) {
-		rc = sqlite3BtreeCommit(sg->pBtree);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-		}
-	}
-
-    return;
-
-close:
-	if (ctxt.n_cursors >= 3) {
-		sqlite3BtreeCloseCursor(crsTokens);
-		ctxt.n_cursors--;
-	}
-
-	close_exprs(&ctxt);
-
-	if (sg->autoCommit) {
-		sqlite3BtreeRollback(sg->pBtree, SQLITE_ABORT_ROLLBACK, 0);
-	}
-}
-
-GuSeq*
-sg_query_linearization(SgSG *sg, GuString tok, GuPool *pool, GuExn* err)
-{
-	int rc;
-
-	BtCursor* crsTokens;
-	rc = sqlite3BtreeCursor(sg->pBtree, sg->tokensTNum, 1, 1, 1, &crsTokens);
-	if (rc != SQLITE_OK) {
-		sg_raise_sqlite(rc, err);
-		return NULL;
-	}
-
-	Mem mem[1];
-	mem[0].flags = MEM_Str;
-	mem[0].n = strlen(tok);
-	mem[0].z = (void*) tok;
-
-	UnpackedRecord idxKey;
-	sqlite3BtreeInitUnpackedRecord(&idxKey, crsTokens, 1, 0, mem);
-
-	int res = 0;
-	rc = sqlite3BtreeMovetoUnpacked(crsTokens,
-									&idxKey, 0,  0, &res);
-	if (rc != SQLITE_OK) {
-		sg_raise_sqlite(rc, err);
-		return NULL;
-	}
-	
-	GuBuf* ids = gu_new_buf(SgId, pool);
-
-	while (res == 0) {
-		SgId key;
-		rc = sqlite3BtreeIdxRowid(sg->pBtree, crsTokens, &key);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			sqlite3BtreeClearCursor(crsTokens);
-			return NULL;
-		}
-
-		gu_buf_push(ids, SgId, key);
-
-		sqlite3BtreeNext(crsTokens, &res);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			sqlite3BtreeClearCursor(crsTokens);
-			return NULL;
-		}
-
-		i64 szData;
-		const unsigned char *zData;
-		rc = sqlite3BtreeKeySize(crsTokens, &szData);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			sqlite3BtreeClearCursor(crsTokens);
-			return NULL;
-		}
-
-		u32 available = 0;
-		zData = sqlite3BtreeKeyFetch(crsTokens, &available);
-		if (szData > available)
-			gu_impossible();
-
-		res = sqlite3BtreeRecordCompare(available, zData, &idxKey);
-		if (res != 0)
-			break;
-	}
-
-	sqlite3BtreeClearCursor(crsTokens);
-	return gu_buf_data_seq(ids);
-}
-
-typedef struct {
-	int n_cursors;
-	BtCursor* cursor[4];
-} TripleContext;
-
-static int
-open_triples(SgSG *sg, int wrFlag, TripleContext* ctxt, GuExn* err)
-{
-	int rc;
-
-	ctxt->n_cursors = 0;
-	while (ctxt->n_cursors < 3) {
-		rc = sqlite3BtreeCursor(sg->pBtree, sg->triplesIdxTNum[ctxt->n_cursors], wrFlag, 3-ctxt->n_cursors, ctxt->n_cursors, &ctxt->cursor[ctxt->n_cursors]);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			return rc;
-		}
-		ctxt->n_cursors++;
-	}
-
-	rc = sqlite3BtreeCursor(sg->pBtree, sg->triplesTNum, wrFlag, 0, 0, &ctxt->cursor[ctxt->n_cursors]);
-	if (rc != SQLITE_OK) {
-		sg_raise_sqlite(rc, err);
-		return rc;
-	}
-	ctxt->n_cursors++;
-
-	return SQLITE_OK;
-}
-
-static void
-close_triples(TripleContext* ctxt)
-{
-	while (ctxt->n_cursors > 0) {
-		ctxt->n_cursors--;
-		sqlite3BtreeCloseCursor(ctxt->cursor[ctxt->n_cursors]);
-	}
-}
-
-SgId
-sg_insert_triple(SgSG *sg, SgTriple triple, GuExn* err)
-{
-	int rc;
-
-	if (sg->autoCommit) {
-		rc = sqlite3BtreeBeginTrans(sg->pBtree, 1);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			return 0;
-		}
-	}
-
-	TripleContext tctxt;
-	rc = open_triples(sg, 1, &tctxt, err);
-	if (rc != SQLITE_OK)
-		goto close;
-
-	Mem mem[4];
-
-	ExprContext ectxt;
-	rc = open_exprs(sg, 1, false, &ectxt, err);
-	if (rc != SQLITE_OK)
-		goto close;
-
-	for (size_t i = 0; i < 3; i++) {
-		mem[i].flags = MEM_Int;
-
-		rc = store_expr(sg, &ectxt, triple[i], &mem[i].u.i, 1);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			goto close;
-		}
-	}
-
-	UnpackedRecord idxKey;
-	sqlite3BtreeInitUnpackedRecord(&idxKey, tctxt.cursor[0], 3, 0, mem);
-
-	int res = 0;
-	rc = sqlite3BtreeMovetoUnpacked(tctxt.cursor[0],
-	                                &idxKey, 0,  0, &res);
-	if (rc != SQLITE_OK) {
-		sg_raise_sqlite(rc, err);
-		goto close;
-	}
-
-	SgId key = 0;
-
-	if (res == 0) {
-		rc = sqlite3BtreeIdxRowid(sg->pBtree, tctxt.cursor[0], &key);
-	} else {
-		rc = sqlite3BtreeLast(tctxt.cursor[3], &res);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			goto close;
-		}
-
-		rc = sqlite3BtreeKeySize(tctxt.cursor[3], &key);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			goto close;
-		}
-		key++;
-
-		u32 serial_type;
-		unsigned char buf[41];  // enough for a record with three integers
-		int file_format = sqlite3BtreeFileFormat(sg->pBtree);
-
-		unsigned char* p = buf+(buf[0] = 5);
-
-		serial_type = sqlite3BtreeSerialType(&mem[0], file_format);
-		buf[1] = serial_type;
-		p += sqlite3BtreeSerialPut(p, &mem[0], serial_type);
-
-		serial_type = sqlite3BtreeSerialType(&mem[1], file_format);
-		buf[2] = serial_type;
-		p += sqlite3BtreeSerialPut(p, &mem[1], serial_type);
-
-		serial_type = sqlite3BtreeSerialType(&mem[2], file_format);
-		buf[3] = serial_type;
-		p += sqlite3BtreeSerialPut(p, &mem[2], serial_type);
-
-		unsigned char* tmp = p;
-
-		mem[3].flags = MEM_Int;
-		mem[3].u.i = 1;
-		serial_type = sqlite3BtreeSerialType(&mem[3], file_format);
-		buf[4] = serial_type;
-		p += sqlite3BtreeSerialPut(p, &mem[3], serial_type);
-
-		rc = sqlite3BtreeInsert(tctxt.cursor[3], 0, key,
-								buf, p-buf, 0,
-								0, 0);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			goto close;
-		}
-
-		mem[3].flags = MEM_Int;
-		mem[3].u.i = key;
-
-		p = tmp;
-		serial_type = sqlite3BtreeSerialType(&mem[3], file_format);
-		buf[4] = serial_type;
-		p += sqlite3BtreeSerialPut(p, &mem[3], serial_type);
-
-		rc = sqlite3BtreeInsert(tctxt.cursor[0], buf, p-buf,
-								0, key, 0,
-								0, 0);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			goto close;
-		}
-
-		p = buf+(buf[0] = 4);
-
-		serial_type = sqlite3BtreeSerialType(&mem[1], file_format);
-		buf[1] = serial_type;
-		p += sqlite3BtreeSerialPut(p, &mem[1], serial_type);
-
-		serial_type = sqlite3BtreeSerialType(&mem[2], file_format);
-		buf[2] = serial_type;
-		p += sqlite3BtreeSerialPut(p, &mem[2], serial_type);
-
-		serial_type = sqlite3BtreeSerialType(&mem[3], file_format);
-		buf[3] = serial_type;
-		p += sqlite3BtreeSerialPut(p, &mem[3], serial_type);
-
-		rc = sqlite3BtreeInsert(tctxt.cursor[1], buf, p-buf,
-								0, key, 0,
-								0, 0);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			goto close;
-		}
-
-		p = buf+(buf[0] = 3);
-
-		serial_type = sqlite3BtreeSerialType(&mem[2], file_format);
-		buf[1] = serial_type;
-		p += sqlite3BtreeSerialPut(p, &mem[2], serial_type);
-
-		serial_type = sqlite3BtreeSerialType(&mem[3], file_format);
-		buf[2] = serial_type;
-		p += sqlite3BtreeSerialPut(p, &mem[3], serial_type);
-
-		rc = sqlite3BtreeInsert(tctxt.cursor[2], buf, p-buf,
-								0, key, 0,
-								0, 0);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			goto close;
-		}
-	}
-
-close:
-	close_exprs(&ectxt);
-	close_triples(&tctxt);
-
-	if (sg->autoCommit) {
-		if (rc == SQLITE_OK || rc == SQLITE_DONE) {
-			rc = sqlite3BtreeCommit(sg->pBtree);
-			if (rc != SQLITE_OK) {
-				sg_raise_sqlite(rc, err);
-				return 0;
-			}
-		} else {
-			sqlite3BtreeRollback(sg->pBtree, SQLITE_ABORT_ROLLBACK, 0);
-		}
-	}
-
-	return key;
-}
-
-static int
-load_triple(BtCursor* crsTriples, BtCursor* crsExprs, SgTriple triple,
-            GuPool* out_pool)
-{
-	int rc;
-
-	u32 payloadSize;
-	rc = sqlite3BtreeDataSize(crsTriples, &payloadSize);
-	if (rc != SQLITE_OK)
-		return rc;
-
-	u32 avail = 0;
-	const unsigned char* row = sqlite3BtreeDataFetch(crsTriples, &avail);
-	row++;
-
-	int serial_type_subj, serial_type_pred, serial_type_obj;
-	row += getVarint32(row, serial_type_subj);
-	row += getVarint32(row, serial_type_pred);
-	row += getVarint32(row, serial_type_obj);
-	row++;
-
-	Mem mem[3];
-	row += sqlite3BtreeSerialGet(row, serial_type_subj, &mem[0]);
-	row += sqlite3BtreeSerialGet(row, serial_type_pred, &mem[1]);
-	row += sqlite3BtreeSerialGet(row, serial_type_obj,  &mem[2]);
-
-	for (int i = 0; i < 3; i++) {
-		if (gu_variant_is_null(triple[i])) {
-			rc = load_expr(crsExprs, mem[i].u.i, &triple[i], out_pool);
-			if (rc != SQLITE_OK)
-				return rc;
-		}
-	}
-
-	return SQLITE_OK;
-}
-
-int
-sg_get_triple(SgSG *sg, SgId key, SgTriple triple,
-              GuPool* out_pool, GuExn* err)
-{
-	triple[0] = gu_null_variant;
-	triple[1] = gu_null_variant;
-	triple[2] = gu_null_variant;
-
-	int rc;
-	if (sg->autoCommit) {
-		rc = sqlite3BtreeBeginTrans(sg->pBtree, 0);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			return false;
-		}
-	}
-
-	BtCursor* crsTriples;
-	rc = sqlite3BtreeCursor(sg->pBtree, sg->triplesTNum, 0, 0, 0, &crsTriples);
-	if (rc != SQLITE_OK) {
-		sg_raise_sqlite(rc, err);
-		goto rollback;
-	}
-
-	BtCursor* crsExprs;
-	rc = sqlite3BtreeCursor(sg->pBtree, sg->exprsTNum, 0, 0, 0, &crsExprs);
-	if (rc != SQLITE_OK) {
-		sg_raise_sqlite(rc, err);
-		goto close1;
-	}
-
-	int res;
-	rc = sqlite3BtreeMovetoUnpacked(crsTriples, 0, key, 0, &res);
-	if (rc != SQLITE_OK) {
-		sg_raise_sqlite(rc, err);
-		goto close;
-	}
-
-	if (res == 0) {
-		rc = load_triple(crsTriples, crsExprs, triple, out_pool);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			goto close;
-		}
-	}
-
-	rc = sqlite3BtreeCloseCursor(crsExprs);
-	if (rc != SQLITE_OK) {
-		sg_raise_sqlite(rc, err);
-		goto close1;
-	}
-
-	rc = sqlite3BtreeCloseCursor(crsTriples);
-	if (rc != SQLITE_OK) {
-		sg_raise_sqlite(rc, err);
-		goto rollback;
-	}
-
-	if (sg->autoCommit) {
-		rc = sqlite3BtreeCommit(sg->pBtree);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			return false;
-		}
-	}
-
-	return (res == 0);
-
-close:
-	sqlite3BtreeCloseCursor(crsExprs);
-
-close1:
-	sqlite3BtreeCloseCursor(crsTriples);
-
-rollback:
-	if (sg->autoCommit) {
-		sqlite3BtreeRollback(sg->pBtree, SQLITE_ABORT_ROLLBACK, 0);
-	}
-	return false;
-}
-
-typedef struct {
-	TripleContext tctxt;
-
-	BtCursor* cursor;
-
-	int res;
-	Mem mem[3];
-	UnpackedRecord idxKey;
-}  SgTripleResultInt;
-
-struct SgTripleResult {
-	SgSG *sg;
-	SgTriple triple;
-	ExprContext ectxt;
-	
-	SgTripleResultInt i;
-};
-
-static int
-triple_result_init(SgSG *sg, SgTripleResultInt* tresi, GuExn* err)
-{
-	int rc;
-
-	rc = open_triples(sg, 0, &tresi->tctxt, err);
-	if (rc != SQLITE_OK)
-		return rc;
-
-	int i = 0;
-	while (i < 3) {
-		if (tresi->mem[i].flags != MEM_Null)
-			break;
-		i++;
-	}
-
-	tresi->cursor = tresi->tctxt.cursor[i];
-	sqlite3BtreeInitUnpackedRecord(&tresi->idxKey, tresi->cursor, 0, 0, &tresi->mem[i]);
-	tresi->res = 0;
-
-	while (i+tresi->idxKey.nField < 3) {
-		tresi->idxKey.nField++;
-
-		if (tresi->mem[i+tresi->idxKey.nField].flags == MEM_Null)
-			break;
-	}
-
-	if (tresi->idxKey.nField > 0) {
-		tresi->idxKey.default_rc = 1;
-		rc = sqlite3BtreeMovetoUnpacked(tresi->cursor,
-										&tresi->idxKey, 0,  0, &tresi->res);
-		if (rc == SQLITE_OK) {
-			if (tresi->res < 0) {
-				rc = sqlite3BtreeNext(tresi->cursor, &tresi->res);
-			}
-			tresi->res = 0;
-		}
-	} else {
-		rc = sqlite3BtreeFirst(tresi->cursor, &tresi->res);
-	}
-
-	if (rc != SQLITE_OK) {
-		sg_raise_sqlite(rc, err);
-	}
-
-	return rc;
-}
-
-static bool
-triple_result_fetch(SgSG* sg,
-                    SgTripleResultInt* tresi,
-                    SgId* pKey, GuExn* err)
-{
-	while (tresi->res == 0) {
-		int rc;
-
-		if (tresi->idxKey.nField > 0) {
-			i64 szData;
-			const unsigned char *zData;
-			rc = sqlite3BtreeKeySize(tresi->cursor, &szData);
-			if (rc != SQLITE_OK) {
-				sg_raise_sqlite(rc, err);
-				return false;
-			}
-
-			u32 available = 0;
-			zData = sqlite3BtreeKeyFetch(tresi->cursor, &available);
-			if (szData > available)
-				gu_impossible();
-
-			tresi->idxKey.default_rc = 0;
-			tresi->res = sqlite3BtreeRecordCompare(available, zData, &tresi->idxKey);
-			if (tresi->res != 0)
-				return false;
-
-			if (tresi->idxKey.aMem == &tresi->mem[0] &&
-			    tresi->idxKey.nField == 1 &&
-			    tresi->mem[2].flags != MEM_Null) {
-				int offset = 
-					zData[0] + 
-					sqlite3BtreeSerialTypeLen(zData[1]) + 
-					sqlite3BtreeSerialTypeLen(zData[2]);
-				zData+offset;
-				Mem mem;
-				sqlite3BtreeSerialGet(zData+offset, zData[3], &mem);
-				if (mem.u.i != tresi->mem[2].u.i) {
-					sqlite3BtreeNext(tresi->cursor, &tresi->res);
-					if (rc != SQLITE_OK) {
-						sg_raise_sqlite(rc, err);
-						return false;
-					}
-					continue;
-				}
-			}
-
-			rc = sqlite3BtreeIdxRowid(sg->pBtree, tresi->cursor, pKey);
-			if (rc != SQLITE_OK) {
-				sg_raise_sqlite(rc, err);
-				return false;
-			}
-
-			rc = sqlite3BtreeMovetoUnpacked(tresi->tctxt.cursor[3], 0, *pKey, 0, &tresi->res);
-		} else {
-			rc = sqlite3BtreeKeySize(tresi->cursor, pKey);
-		}
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			return false;
-		}
-
-		return true;
-	}
-
-	return false;
-}
-
-SgTripleResult*
-sg_query_triple(SgSG *sg, SgTriple triple, GuExn* err)
-{
-	int rc;
-
-	if (sg->autoCommit) {
-		rc = sqlite3BtreeBeginTrans(sg->pBtree, 0);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			return NULL;
-		}
-	}
-
-	SgTripleResult* tres = malloc(sizeof(SgTripleResult));
-	tres->sg = sg;
-	tres->triple[0] = triple[0];
-	tres->triple[1] = triple[1];
-	tres->triple[2] = triple[2];
-
-	rc = open_exprs(sg, 0, false, &tres->ectxt, err);
-	if (rc != SQLITE_OK)
-		goto close;
-
-	for (int i = 0; i < 3; i++) {
-		if (gu_variant_is_null(triple[i]))
-			tres->i.mem[i].flags = MEM_Null;
-		else {
-			tres->i.mem[i].flags = MEM_Int;
-			rc = store_expr(sg, &tres->ectxt, triple[i], &tres->i.mem[i].u.i, 0);
-			if (rc != SQLITE_OK)
-				goto close;
-			if (tres->i.mem[i].u.i == 0) {
-				tres->i.res = 1;
-				tres->i.tctxt.n_cursors = 0; // this is important since the triples are not initialized yet
-				return tres;
-			}
-		}
-	}
-
-	rc = triple_result_init(sg, &tres->i, err);
-	if (rc != SQLITE_OK) {
-		return NULL;
-	}
-
-	return tres;
-
-close:
-	close_exprs(&tres->ectxt);
-
-	if (sg->autoCommit) {
-		sqlite3BtreeRollback(sg->pBtree, SQLITE_ABORT_ROLLBACK, 0);
-	}
-
-	free(tres);
-	return NULL;
-}
-
-int
-sg_triple_result_fetch(SgTripleResult* tres, SgId* pKey, SgTriple triple,
-                       GuPool* out_pool, GuExn* err)
-{
-	int rc;
-
-	triple[0] = tres->triple[0];
-	triple[1] = tres->triple[1];
-	triple[2] = tres->triple[2];
-
-	bool found =
-		triple_result_fetch(tres->sg, &tres->i, pKey, err);
-	if (!found)
-		return 0;
-
-	rc = load_triple(tres->i.tctxt.cursor[3], tres->ectxt.crsExprs,
-		             triple, out_pool);
-	if (rc != SQLITE_OK) {
-		sg_raise_sqlite(rc, err);
-		return 0;
-	}
-		
-	sqlite3BtreeNext(tres->i.cursor, &tres->i.res);
-	if (rc != SQLITE_OK) {
-		sg_raise_sqlite(rc, err);
-		return 0;
-	}
-
-	return 1;
-}
-
-void
-sg_triple_result_get_query(SgTripleResult* tres, SgTriple triple)
-{
-	triple[0] = tres->triple[0];
-	triple[1] = tres->triple[1];
-	triple[2] = tres->triple[2];
-}
-
-void
-sg_triple_result_close(SgTripleResult* tres, GuExn* err)
-{
-	close_exprs(&tres->ectxt);
-	close_triples(&tres->i.tctxt);
-
-	if (tres->sg->autoCommit) {
-		int rc = sqlite3BtreeCommit(tres->sg->pBtree);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			return;
-		}
-	}
-
-	free(tres);
-}
-
-typedef int SgPattern[3];
-
-struct SgQueryResult {
-	SgSG* sg;
-
-	size_t n_vars;
-	struct {
-		SgId id;
-		PgfExpr expr;
-	}* vars;
-
-	size_t n_sels;
-	int* sels;
-
-	ExprContext ectxt;
-	bool is_empty;
-
-	size_t n_results;
-	size_t n_patterns;
-	struct {
-		SgPattern pattern;
-		SgTripleResultInt result;
-	} triples[];
-};
-
-SgQueryResult*
-sg_query(SgSG *sg, size_t n_triples, SgTriple* triples, GuExn* err)
-{
-	int rc;
-
-	if (sg->autoCommit) {
-		rc = sqlite3BtreeBeginTrans(sg->pBtree, 0);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			return NULL;
-		}
-	}
-
-	SgQueryResult* qres = malloc(GU_FLEX_SIZE(SgQueryResult, triples, n_triples));
-	qres->sg        = sg;
-	qres->is_empty  = false;
-	qres->n_results = 0;
-
-	qres->n_vars = 0;
-	qres->vars   = malloc(sizeof(qres->vars[0])*n_triples*3);
-
-	qres->n_sels = 0;
-	qres->sels   = malloc(sizeof(int)*n_triples*3);
-
-	rc = open_exprs(sg, 0, false, &qres->ectxt, err);
-	if (rc != SQLITE_OK)
-		goto close;
-
-	qres->n_patterns = n_triples;
-	for (size_t i = 0; i < n_triples; i++) {
-		for (int k = 0; k < 3; k++) {
-			PgfExpr expr = triples[i][k];
-
-			size_t j = 0;
-			while (j < qres->n_vars) {
-				if (pgf_expr_eq(expr, qres->vars[j].expr))
-					break;
-				j++;
-			}
-			if (j >= qres->n_vars) {
-				qres->vars[j].expr = expr;
-
-				if (gu_variant_tag(expr) == PGF_EXPR_META) {
-					qres->vars[j].id = 0;
-					qres->sels[qres->n_sels++] = j;
-					qres->triples[i].result.mem[k].flags = MEM_Null;
-				} else {
-					rc = store_expr(sg, &qres->ectxt, expr, &qres->vars[j].id, 0);
-					if (rc != SQLITE_OK) {
-						sg_raise_sqlite(rc, err);
-						goto close;
-					}
-
-					if (qres->vars[j].id == 0)
-						goto close;
-
-					qres->triples[i].result.mem[k].flags = MEM_Int;
-				}
-
-				qres->n_vars++;
-			} else {
-				qres->triples[i].result.mem[k].flags = MEM_Int;
-			}
-
-			qres->triples[i].pattern[k] = j;
-		}
-	}
-
-	return qres;
-
-close:
-	qres->is_empty = true;
-
-	close_exprs(&qres->ectxt);
-
-	if (sg->autoCommit) {
-		sqlite3BtreeRollback(sg->pBtree, SQLITE_ABORT_ROLLBACK, 0);
-	}
-
-	return qres;
-}
-
-size_t
-sg_query_result_columns(SgQueryResult* qres) {
-	return qres->n_sels;
-}
-
-static int
-load_vars(SgQueryResult* qres, BtCursor* crsTriples, SgPattern pattern)
-{
-	int rc;
-
-	u32 payloadSize;
-	rc = sqlite3BtreeDataSize(crsTriples, &payloadSize);
-	if (rc != SQLITE_OK)
-		return rc;
-
-	u32 avail = 0;
-	const unsigned char* row = sqlite3BtreeDataFetch(crsTriples, &avail);
-	row++;
-
-	int serial_type_subj, serial_type_pred, serial_type_obj;
-	row += getVarint32(row, serial_type_subj);
-	row += getVarint32(row, serial_type_pred);
-	row += getVarint32(row, serial_type_obj);
-	row++;
-
-	Mem mem[3];
-	row += sqlite3BtreeSerialGet(row, serial_type_subj, &mem[0]);
-	row += sqlite3BtreeSerialGet(row, serial_type_pred, &mem[1]);
-	row += sqlite3BtreeSerialGet(row, serial_type_obj,  &mem[2]);
-
-	for (int i = 0; i < 3; i++) {
-		qres->vars[pattern[i]].id = mem[i].u.i;
-	}
-
-	return SQLITE_OK;
-}
-
-int
-query_result_next(SgQueryResult* qres, GuExn* err)
-{
-	if (qres->is_empty)
-		return 0;
-
-	int rc;
-
-	SgId key;
-	size_t i = (qres->n_results == 0) ? 0 : qres->n_results-1;
-	while (i < qres->n_patterns) {
-		if (i >= qres->n_results) {
-			for (int k = 0; k < 3; k++) {
-				qres->triples[i].result.mem[k].u.i = qres->vars[qres->triples[i].pattern[k]].id;
-			}
-
-			rc = triple_result_init(qres->sg, &qres->triples[i].result, err);
-			if (rc != SQLITE_OK) {
-				goto close;
-			}
-
-			qres->n_results++;
-		}
-
-		bool found =
-			triple_result_fetch(qres->sg,
-								&qres->triples[i].result,
-								&key, err);
-		if (gu_exn_is_raised(err)) {
-			goto close;
-		}
-
-		if (found) {
-			rc = sqlite3BtreeNext(qres->triples[i].result.cursor, &qres->triples[i].result.res);
-			if (rc != SQLITE_OK) {
-				sg_raise_sqlite(rc, err);
-				goto close;
-			}
-
-			rc = load_vars(qres, qres->triples[i].result.tctxt.cursor[3], qres->triples[i].pattern);
-			if (rc != SQLITE_OK) {
-				sg_raise_sqlite(rc, err);
-				goto close;
-			}
-
-			i++;
-		} else {
-			close_triples(&qres->triples[i].result.tctxt);
-
-			if (i == 0)
-				goto close;
-
-			i--;
-			qres->n_results--;
-		}
-	}
-
-close:
-	qres->is_empty = true;
-	return 0;
-}
-
-int
-sg_query_result_fetch(SgQueryResult* qres, PgfExpr* res, 
-                      GuPool* out_pool, GuExn* err)
-{
-	if (!query_result_next(qres, err))
-		return 0;
-
-	for (size_t i = 0; i < qres->n_sels; i++) {
-		int rc = load_expr(qres->ectxt.crsExprs,
-		                   qres->vars[qres->sels[i]].id,
-		                   &res[i], out_pool);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			qres->is_empty = true;
-			return 0;
-		}
-	}
-
-	return 1;
-}
-
-static PgfExpr
-instantiate_expr(SgQueryResult* qres, PgfExpr expr,
-                 GuPool* out_pool, GuExn* err)
-{
-	PgfExpr new_expr = gu_null_variant;
-
-	GuVariantInfo ei = gu_variant_open(expr);
-	switch (ei.tag) {
-	case PGF_EXPR_ABS: {
-		PgfExprAbs* abs = ei.data;
-
-		PgfExprAbs* new_abs =
-			gu_new_variant(PGF_EXPR_ABS,
-			               PgfExprAbs,
-			               &new_expr, out_pool);
-		new_abs->bind_type = abs->bind_type;
-		new_abs->id        = gu_string_copy(abs->id, out_pool);
-		new_abs->body      = instantiate_expr(qres, abs->body, out_pool, err);
-		break;
-	}
-	case PGF_EXPR_APP: {
-		PgfExprApp* app = ei.data;
-		
-		PgfExprApp* new_app =
-			gu_new_variant(PGF_EXPR_APP,
-			               PgfExprApp,
-			               &new_expr, out_pool);
-		new_app->fun = instantiate_expr(qres, app->fun, out_pool, err);
-		new_app->arg = instantiate_expr(qres, app->arg, out_pool, err);
-		break;
-	}
-	case PGF_EXPR_LIT: {
-		PgfExprLit* lit = ei.data;
-
-		PgfExprLit* new_lit =
-			gu_new_variant(PGF_EXPR_LIT,
-			               PgfExprLit,
-			               &new_expr, out_pool);
-
-		GuVariantInfo i = gu_variant_open(lit->lit);
-		switch (i.tag) {
-		case PGF_LITERAL_STR: {
-			PgfLiteralStr* lstr = i.data;
-
-			PgfLiteralStr* new_lstr =
-				gu_new_flex_variant(PGF_LITERAL_STR,
-				                    PgfLiteralStr,
-				                    val, strlen(lstr->val)+1,
-				                    &new_lit->lit, out_pool);
-			strcpy(new_lstr->val, lstr->val);
-			break;
-		}
-		case PGF_LITERAL_INT: {
-			PgfLiteralInt* lint = i.data;
-
-			PgfLiteralInt* new_lint =
-				gu_new_variant(PGF_LITERAL_INT,
-				               PgfLiteralInt,
-				               &new_lit->lit, out_pool);
-			new_lint->val = lint->val;
-			break;
-		}
-		case PGF_LITERAL_FLT: {
-			PgfLiteralFlt* lflt = i.data;
-
-			PgfLiteralFlt* new_lflt =
-				gu_new_variant(PGF_LITERAL_FLT,
-				               PgfLiteralFlt,
-				               &new_lit->lit, out_pool);
-			new_lflt->val = lflt->val;
-			break;
-		}
-		default:
-			gu_impossible();
-		}
-
-		break;
-	}
-	case PGF_EXPR_META: {
-		new_expr = expr;
-
-		size_t j = 0;
-		while (j < qres->n_vars) {
-			if (pgf_expr_eq(expr, qres->vars[j].expr)) {
-				
-				int rc = load_expr(qres->ectxt.crsExprs,
-		                           qres->vars[j].id,
-		                           &new_expr, out_pool);
-				if (rc != SQLITE_OK) {
-					sg_raise_sqlite(rc, err);
-					qres->is_empty = true;
-					return new_expr;
-				}
-				break;
-			}
-			j++;
-		}
-
-		break;
-	}
-	case PGF_EXPR_FUN: {
-		PgfExprFun* fun = ei.data;
-		
-		PgfExprFun *new_fun =
-			gu_new_flex_variant(PGF_EXPR_FUN,
-			                    PgfExprFun,
-			                    fun, strlen(fun->fun)+1,
-			                    &new_expr, out_pool);
-		strcpy(new_fun->fun, fun->fun);
-		break;
-	}
-	case PGF_EXPR_VAR: {
-		PgfExprVar* var = ei.data;
-
-		PgfExprVar* new_var =
-			gu_new_variant(PGF_EXPR_VAR,
-						   PgfExprVar,
-						   &new_expr, out_pool);
-		new_var->var = var->var;
-		break;
-	}
-	case PGF_EXPR_TYPED: {
-		break;
-	}
-	case PGF_EXPR_IMPL_ARG: {
-		PgfExprImplArg* impl = ei.data;
-		
-		PgfExprImplArg* new_impl =
-			gu_new_variant(PGF_EXPR_IMPL_ARG,
-			               PgfExprImplArg,
-			               &new_expr, out_pool);
-		new_impl->expr = instantiate_expr(qres, impl->expr, out_pool, err);
-		break;
-	}
-	default:
-		gu_impossible();
-	}
-	
-	return new_expr;
-}
-
-PgfExpr
-sg_query_result_fetch_expr(SgQueryResult* qres, PgfExpr expr,
-                           GuPool* out_pool, GuExn* err)
-{
-	if (!query_result_next(qres, err))
-		return gu_null_variant;
-
-	return instantiate_expr(qres, expr, out_pool, err);
-}
-
-void
-sg_query_result_close(SgQueryResult* qres, GuExn* err)
-{
-	while (qres->n_results > 0) {
-		close_triples(&qres->triples[qres->n_results-1].result.tctxt);
-		qres->n_results--;
-	}
-
-	close_exprs(&qres->ectxt);
-
-	if (qres->sg->autoCommit) {
-		int rc = sqlite3BtreeCommit(qres->sg->pBtree);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			return;
-		}
-	}
-
-	free(qres->vars);
-	free(qres->sels);
-	free(qres);
-}