path: root/src/third_party/wiredtiger/src/cursor/cur_std.c

/*-
 * Copyright (c) 2014-2018 MongoDB, Inc.
 * Copyright (c) 2008-2014 WiredTiger, Inc.
 *	All rights reserved.
 *
 * See the file LICENSE for redistribution information.
 */

#include "wt_internal.h"

/*
 * __wt_cursor_noop --
 *	Cursor noop.
 */
int
__wt_cursor_noop(WT_CURSOR *cursor)
{
	WT_UNUSED(cursor);

	return (0);
}

/*
 * __wt_cursor_cached --
 *	No actions on a closed and cached cursor are allowed.
 */
int
__wt_cursor_cached(WT_CURSOR *cursor)
{
	WT_SESSION_IMPL *session;

	session = (WT_SESSION_IMPL *)cursor->session;
	WT_RET_MSG(session, ENOTSUP, "Cursor has been closed");
}

/*
 * __wt_cursor_notsup --
 *	Unsupported cursor actions.
 */
int
__wt_cursor_notsup(WT_CURSOR *cursor)
{
	WT_SESSION_IMPL *session;

	session = (WT_SESSION_IMPL *)cursor->session;
	WT_RET_MSG(session, ENOTSUP, "Unsupported cursor operation");
}

/*
 * __wt_cursor_get_value_notsup --
 *	WT_CURSOR.get_value not-supported.
 */
int
__wt_cursor_get_value_notsup(WT_CURSOR *cursor, ...)
{
	return (__wt_cursor_notsup(cursor));
}

/*
 * __wt_cursor_set_key_notsup --
 *	WT_CURSOR.set_key not-supported.
 */
void
__wt_cursor_set_key_notsup(WT_CURSOR *cursor, ...)
{
	WT_IGNORE_RET(__wt_cursor_notsup(cursor));
}

/*
 * __wt_cursor_set_value_notsup --
 *	WT_CURSOR.set_value not-supported.
 */
void
__wt_cursor_set_value_notsup(WT_CURSOR *cursor, ...)
{
	WT_IGNORE_RET(__wt_cursor_notsup(cursor));
}

/*
 * __wt_cursor_compare_notsup --
 *	Unsupported cursor comparison.
 */
int
__wt_cursor_compare_notsup(WT_CURSOR *a, WT_CURSOR *b, int *cmpp)
{
	WT_UNUSED(b);
	WT_UNUSED(cmpp);

	return (__wt_cursor_notsup(a));
}

/*
 * __wt_cursor_equals_notsup --
 *	Unsupported cursor equality.
 */
int
__wt_cursor_equals_notsup(WT_CURSOR *cursor, WT_CURSOR *other, int *equalp)
{
	WT_UNUSED(other);
	WT_UNUSED(equalp);

	return (__wt_cursor_notsup(cursor));
}

/*
 * __wt_cursor_modify_notsup --
 *	Unsupported cursor modify.
 */
int
__wt_cursor_modify_notsup(WT_CURSOR *cursor, WT_MODIFY *entries, int nentries)
{
	WT_SESSION_IMPL *session;

	WT_UNUSED(entries);
	WT_UNUSED(nentries);

	if (cursor->value_format != NULL && strlen(cursor->value_format) != 0) {
		session = (WT_SESSION_IMPL *)cursor->session;
		WT_RET_MSG(session, ENOTSUP,
		    "WT_CURSOR.modify only supported for 'S' and 'u' value "
		    "formats");
	}
	return (__wt_cursor_notsup(cursor));
}

/*
 * __wt_cursor_search_near_notsup --
 *	Unsupported cursor search-near.
 */
int
__wt_cursor_search_near_notsup(WT_CURSOR *cursor, int *exact)
{
	WT_UNUSED(exact);

	return (__wt_cursor_notsup(cursor));
}

/*
 * __wt_cursor_reconfigure_notsup --
 *	Unsupported cursor reconfiguration.
 */
int
__wt_cursor_reconfigure_notsup(WT_CURSOR *cursor, const char *config)
{
	WT_UNUSED(config);

	return (__wt_cursor_notsup(cursor));
}

/*
 * __wt_cursor_reopen_notsup --
 *	Unsupported cursor reopen.
 */
int
__wt_cursor_reopen_notsup(WT_CURSOR *cursor, bool check_only)
{
	WT_UNUSED(check_only);

	return (__wt_cursor_notsup(cursor));
}

/*
 * __wt_cursor_set_notsup --
 *	Reset the cursor methods to not-supported.
 */
void
__wt_cursor_set_notsup(WT_CURSOR *cursor)
{
	/*
	 * Set cursor methods other than close, reconfigure and reset, to fail.
	 * Close is unchanged so the cursor can be discarded; reset is set to
	 * a no-op because session transactional operations reset all of the
	 * cursors in a session. Reconfigure is left open in case it's possible
	 * in the future to change these configurations.
	 */
	cursor->compare = __wt_cursor_compare_notsup;
	cursor->insert = __wt_cursor_notsup;
	cursor->modify = __wt_cursor_modify_notsup;
	cursor->next = __wt_cursor_notsup;
	cursor->prev = __wt_cursor_notsup;
	cursor->remove = __wt_cursor_notsup;
	cursor->reserve = __wt_cursor_notsup;
	cursor->reset = __wt_cursor_noop;
	cursor->search = __wt_cursor_notsup;
	cursor->search_near = __wt_cursor_search_near_notsup;
	cursor->update = __wt_cursor_notsup;
}

/*
 * __wt_cursor_kv_not_set --
 *	Standard error message for key/values not set.
 */
int
__wt_cursor_kv_not_set(WT_CURSOR *cursor, bool key)
    WT_GCC_FUNC_ATTRIBUTE((cold))
{
	WT_SESSION_IMPL *session;

	session = (WT_SESSION_IMPL *)cursor->session;

	WT_RET_MSG(session,
	    cursor->saved_err == 0 ? EINVAL : cursor->saved_err,
	    "requires %s be set", key ? "key" : "value");
}

/*
 * __wt_cursor_get_key --
 *	WT_CURSOR->get_key default implementation.
 */
int
__wt_cursor_get_key(WT_CURSOR *cursor, ...)
{
	WT_DECL_RET;
	va_list ap;

	va_start(ap, cursor);
	ret = __wt_cursor_get_keyv(cursor, cursor->flags, ap);
	va_end(ap);
	return (ret);
}

/*
 * __wt_cursor_set_key --
 *	WT_CURSOR->set_key default implementation.
 */
void
__wt_cursor_set_key(WT_CURSOR *cursor, ...)
{
	va_list ap;

	va_start(ap, cursor);
	__wt_cursor_set_keyv(cursor, cursor->flags, ap);
	va_end(ap);
}

/*
 * __wt_cursor_get_raw_key --
 *	Temporarily force raw mode in a cursor to get a canonical copy of
 * the key.
 */
int
__wt_cursor_get_raw_key(WT_CURSOR *cursor, WT_ITEM *key)
{
	WT_DECL_RET;
	bool raw_set;

	raw_set = F_ISSET(cursor, WT_CURSTD_RAW);
	if (!raw_set)
		F_SET(cursor, WT_CURSTD_RAW);
	ret = cursor->get_key(cursor, key);
	if (!raw_set)
		F_CLR(cursor, WT_CURSTD_RAW);
	return (ret);
}

/*
 * __wt_cursor_set_raw_key --
 *	Temporarily force raw mode in a cursor to set a canonical copy of
 * the key.
 */
void
__wt_cursor_set_raw_key(WT_CURSOR *cursor, WT_ITEM *key)
{
	bool raw_set;

	raw_set = F_ISSET(cursor, WT_CURSTD_RAW);
	if (!raw_set)
		F_SET(cursor, WT_CURSTD_RAW);
	cursor->set_key(cursor, key);
	if (!raw_set)
		F_CLR(cursor, WT_CURSTD_RAW);
}

/*
 * __wt_cursor_get_raw_value --
 *	Temporarily force raw mode in a cursor to get a canonical copy of
 * the value.
 */
int
__wt_cursor_get_raw_value(WT_CURSOR *cursor, WT_ITEM *value)
{
	WT_DECL_RET;
	bool raw_set;

	raw_set = F_ISSET(cursor, WT_CURSTD_RAW);
	if (!raw_set)
		F_SET(cursor, WT_CURSTD_RAW);
	ret = cursor->get_value(cursor, value);
	if (!raw_set)
		F_CLR(cursor, WT_CURSTD_RAW);
	return (ret);
}

/*
 * __wt_cursor_set_raw_value --
 *	Temporarily force raw mode in a cursor to set a canonical copy of
 * the value.
 */
void
__wt_cursor_set_raw_value(WT_CURSOR *cursor, WT_ITEM *value)
{
	bool raw_set;

	raw_set = F_ISSET(cursor, WT_CURSTD_RAW);
	if (!raw_set)
		F_SET(cursor, WT_CURSTD_RAW);
	cursor->set_value(cursor, value);
	if (!raw_set)
		F_CLR(cursor, WT_CURSTD_RAW);
}

/*
 * __wt_cursor_get_keyv --
 *	WT_CURSOR->get_key worker function.
 */
int
__wt_cursor_get_keyv(WT_CURSOR *cursor, uint32_t flags, va_list ap)
{
	WT_DECL_RET;
	WT_ITEM *key;
	WT_SESSION_IMPL *session;
	size_t size;
	const char *fmt;

	CURSOR_API_CALL(cursor, session, get_key, NULL);
	if (!F_ISSET(cursor, WT_CURSTD_KEY_SET))
		WT_ERR(__wt_cursor_kv_not_set(cursor, true));

	if (WT_CURSOR_RECNO(cursor)) {
		if (LF_ISSET(WT_CURSTD_RAW)) {
			key = va_arg(ap, WT_ITEM *);
			key->data = cursor->raw_recno_buf;
			WT_ERR(__wt_struct_size(
			    session, &size, "q", cursor->recno));
			key->size = size;
			ret = __wt_struct_pack(session, cursor->raw_recno_buf,
			    sizeof(cursor->raw_recno_buf), "q", cursor->recno);
		} else
			*va_arg(ap, uint64_t *) = cursor->recno;
	} else {
		/* Fast path some common cases. */
		fmt = cursor->key_format;
		if (LF_ISSET(WT_CURSOR_RAW_OK) || WT_STREQ(fmt, "u")) {
			key = va_arg(ap, WT_ITEM *);
			key->data = cursor->key.data;
			key->size = cursor->key.size;
		} else if (WT_STREQ(fmt, "S"))
			*va_arg(ap, const char **) = cursor->key.data;
		else
			ret = __wt_struct_unpackv(session,
			    cursor->key.data, cursor->key.size, fmt, ap);
	}

err:	API_END_RET(session, ret);
}

/*
 * __wt_cursor_set_keyv --
 *	WT_CURSOR->set_key default implementation.
 */
void
__wt_cursor_set_keyv(WT_CURSOR *cursor, uint32_t flags, va_list ap)
{
	WT_DECL_RET;
	WT_ITEM *buf, *item, tmp;
	WT_SESSION_IMPL *session;
	size_t sz;
	const char *fmt, *str;
	va_list ap_copy;

	buf = &cursor->key;
	tmp.mem = NULL;

	CURSOR_API_CALL(cursor, session, set_key, NULL);
	if (F_ISSET(cursor, WT_CURSTD_KEY_SET) && WT_DATA_IN_ITEM(buf)) {
		tmp = *buf;
		buf->mem = NULL;
		buf->memsize = 0;
	}

	F_CLR(cursor, WT_CURSTD_KEY_SET);

	if (WT_CURSOR_RECNO(cursor)) {
		if (LF_ISSET(WT_CURSTD_RAW)) {
			item = va_arg(ap, WT_ITEM *);
			WT_ERR(__wt_struct_unpack(session,
			    item->data, item->size, "q", &cursor->recno));
		} else
			cursor->recno = va_arg(ap, uint64_t);
		if (cursor->recno == WT_RECNO_OOB)
			WT_ERR_MSG(session, EINVAL,
			    "%d is an invalid record number", WT_RECNO_OOB);
		buf->data = &cursor->recno;
		sz = sizeof(cursor->recno);
	} else {
		/* Fast path some common cases and special case WT_ITEMs. */
		fmt = cursor->key_format;
		if (LF_ISSET(WT_CURSOR_RAW_OK | WT_CURSTD_DUMP_JSON) ||
		    WT_STREQ(fmt, "u")) {
			item = va_arg(ap, WT_ITEM *);
			sz = item->size;
			buf->data = item->data;
		} else if (WT_STREQ(fmt, "S")) {
			str = va_arg(ap, const char *);
			sz = strlen(str) + 1;
			buf->data = (void *)str;
		} else {
			va_copy(ap_copy, ap);
			ret = __wt_struct_sizev(
			    session, &sz, cursor->key_format, ap_copy);
			va_end(ap_copy);
			WT_ERR(ret);

			WT_ERR(__wt_buf_initsize(session, buf, sz));
			WT_ERR(__wt_struct_packv(
			    session, buf->mem, sz, cursor->key_format, ap));
		}
	}
	if (sz == 0)
		WT_ERR_MSG(session, EINVAL, "Empty keys not permitted");
	else if ((uint32_t)sz != sz)
		WT_ERR_MSG(session, EINVAL,
		    "Key size (%" PRIu64 ") out of range", (uint64_t)sz);
	cursor->saved_err = 0;
	buf->size = sz;
	F_SET(cursor, WT_CURSTD_KEY_EXT);
	if (0) {
err:		cursor->saved_err = ret;
	}

	/*
	 * If we copied the key, either put the memory back into the cursor,
	 * or if we allocated some memory in the meantime, free it.
	 */
	if (tmp.mem != NULL) {
		if (buf->mem == NULL) {
			buf->mem = tmp.mem;
			buf->memsize = tmp.memsize;
		} else
			__wt_free(session, tmp.mem);
	}
	API_END(session, ret);
}

/*
 * __wt_cursor_get_value --
 *	WT_CURSOR->get_value default implementation.
 */
int
__wt_cursor_get_value(WT_CURSOR *cursor, ...)
{
	WT_DECL_RET;
	va_list ap;

	va_start(ap, cursor);
	ret = __wt_cursor_get_valuev(cursor, ap);
	va_end(ap);
	return (ret);
}

/*
 * __wt_cursor_get_valuev --
 *	WT_CURSOR->get_value worker implementation.
 */
int
__wt_cursor_get_valuev(WT_CURSOR *cursor, va_list ap)
{
	WT_DECL_RET;
	WT_ITEM *value;
	WT_SESSION_IMPL *session;
	const char *fmt;

	CURSOR_API_CALL(cursor, session, get_value, NULL);

	if (!F_ISSET(cursor, WT_CURSTD_VALUE_EXT | WT_CURSTD_VALUE_INT))
		WT_ERR(__wt_cursor_kv_not_set(cursor, false));

	/* Fast path some common cases. */
	fmt = cursor->value_format;
	if (F_ISSET(cursor, WT_CURSOR_RAW_OK) || WT_STREQ(fmt, "u")) {
		value = va_arg(ap, WT_ITEM *);
		value->data = cursor->value.data;
		value->size = cursor->value.size;
	} else if (WT_STREQ(fmt, "S"))
		*va_arg(ap, const char **) = cursor->value.data;
	else if (WT_STREQ(fmt, "t") ||
	    (__wt_isdigit((u_char)fmt[0]) && WT_STREQ(fmt + 1, "t")))
		*va_arg(ap, uint8_t *) = *(uint8_t *)cursor->value.data;
	else
		ret = __wt_struct_unpackv(session,
		    cursor->value.data, cursor->value.size, fmt, ap);

err:	API_END_RET(session, ret);
}

/*
 * __wt_cursor_set_value --
 *	WT_CURSOR->set_value default implementation.
 */
void
__wt_cursor_set_value(WT_CURSOR *cursor, ...)
{
	va_list ap;

	va_start(ap, cursor);
	__wt_cursor_set_valuev(cursor, ap);
	va_end(ap);
}

/*
 * __wt_cursor_set_valuev --
 *	WT_CURSOR->set_value worker implementation.
 */
void
__wt_cursor_set_valuev(WT_CURSOR *cursor, va_list ap)
{
	WT_DECL_RET;
	WT_ITEM *buf, *item, tmp;
	WT_SESSION_IMPL *session;
	size_t sz;
	const char *fmt, *str;
	va_list ap_copy;

	buf = &cursor->value;
	tmp.mem = NULL;

	CURSOR_API_CALL(cursor, session, set_value, NULL);
	if (F_ISSET(cursor, WT_CURSTD_VALUE_SET) && WT_DATA_IN_ITEM(buf)) {
		tmp = *buf;
		buf->mem = NULL;
		buf->memsize = 0;
	}

	F_CLR(cursor, WT_CURSTD_VALUE_SET);

	/* Fast path some common cases. */
	fmt = cursor->value_format;
	if (F_ISSET(cursor, WT_CURSOR_RAW_OK | WT_CURSTD_DUMP_JSON) ||
	    WT_STREQ(fmt, "u")) {
		item = va_arg(ap, WT_ITEM *);
		sz = item->size;
		buf->data = item->data;
	} else if (WT_STREQ(fmt, "S")) {
		str = va_arg(ap, const char *);
		sz = strlen(str) + 1;
		buf->data = str;
	} else if (WT_STREQ(fmt, "t") ||
	    (__wt_isdigit((u_char)fmt[0]) && WT_STREQ(fmt + 1, "t"))) {
		sz = 1;
		WT_ERR(__wt_buf_initsize(session, buf, sz));
		*(uint8_t *)buf->mem = (uint8_t)va_arg(ap, int);
	} else {
		va_copy(ap_copy, ap);
		ret = __wt_struct_sizev(session,
		    &sz, cursor->value_format, ap_copy);
		va_end(ap_copy);
		WT_ERR(ret);
		WT_ERR(__wt_buf_initsize(session, buf, sz));
		WT_ERR(__wt_struct_packv(session, buf->mem, sz,
		    cursor->value_format, ap));
	}
	F_SET(cursor, WT_CURSTD_VALUE_EXT);
	buf->size = sz;

	if (0) {
err:		cursor->saved_err = ret;
	}

	/*
	 * If we copied the value, either put the memory back into the cursor,
	 * or if we allocated some memory in the meantime, free it.
	 */
	if (tmp.mem != NULL) {
		if (buf->mem == NULL) {
			buf->mem = tmp.mem;
			buf->memsize = tmp.memsize;
		} else
			__wt_free(session, tmp.mem);
	}

	API_END(session, ret);
}

/*
 * __wt_cursor_cache --
 *	Add this cursor to the cache.
 */
int
__wt_cursor_cache(WT_CURSOR *cursor, WT_DATA_HANDLE *dhandle)
{
	WT_DECL_RET;
	WT_SESSION_IMPL *session;
	uint64_t bucket;

	session = (WT_SESSION_IMPL *)cursor->session;
	WT_ASSERT(session, !F_ISSET(cursor, WT_CURSTD_CACHED) &&
	    dhandle != NULL);

	WT_TRET(cursor->reset(cursor));

	/* Don't keep buffers allocated for cached cursors. */
	__wt_buf_free(session, &cursor->key);
	__wt_buf_free(session, &cursor->value);

	/*
	 * Acquire a reference while decrementing the in-use counter.
	 * After this point, the dhandle may be marked dead, but the
	 * actual handle won't be removed.
	 */
	session->dhandle = dhandle;
	WT_DHANDLE_ACQUIRE(dhandle);
	__wt_cursor_dhandle_decr_use(session);

	/* Move the cursor from the open list to the caching hash table. */
	if (cursor->uri_hash == 0)
		cursor->uri_hash = __wt_hash_city64(
		    cursor->uri, strlen(cursor->uri));
	bucket = cursor->uri_hash % WT_HASH_ARRAY_SIZE;
	TAILQ_REMOVE(&session->cursors, cursor, q);
	TAILQ_INSERT_HEAD(&session->cursor_cache[bucket], cursor, q);

	(void)__wt_atomic_sub32(&S2C(session)->open_cursor_count, 1);
	WT_STAT_CONN_INCR_ATOMIC(session, cursor_cached_count);
	WT_STAT_DATA_DECR(session, cursor_open_count);
	F_SET(cursor, WT_CURSTD_CACHED);
	return (ret);
}

/*
 * __wt_cursor_reopen --
 *	Reopen this cursor from the cached state.
 */
void
__wt_cursor_reopen(WT_CURSOR *cursor, WT_DATA_HANDLE *dhandle)
{
	WT_SESSION_IMPL *session;
	uint64_t bucket;

	session = (WT_SESSION_IMPL *)cursor->session;
	WT_ASSERT(session, F_ISSET(cursor, WT_CURSTD_CACHED));

	if (dhandle != NULL) {
		session->dhandle = dhandle;
		__wt_cursor_dhandle_incr_use(session);
		WT_DHANDLE_RELEASE(dhandle);
	}
	(void)__wt_atomic_add32(&S2C(session)->open_cursor_count, 1);
	WT_STAT_CONN_DECR_ATOMIC(session, cursor_cached_count);
	WT_STAT_DATA_INCR(session, cursor_open_count);

	bucket = cursor->uri_hash % WT_HASH_ARRAY_SIZE;
	TAILQ_REMOVE(&session->cursor_cache[bucket], cursor, q);
	TAILQ_INSERT_HEAD(&session->cursors, cursor, q);
	F_CLR(cursor, WT_CURSTD_CACHED);
}

/*
 * __wt_cursor_cache_release --
 *	Put the cursor into a cached state, called during cursor close
 * operations.
 */
int
__wt_cursor_cache_release(WT_SESSION_IMPL *session, WT_CURSOR *cursor,
    bool *released)
{
	WT_DECL_RET;

	*released = false;
	if (!F_ISSET(cursor, WT_CURSTD_CACHEABLE) ||
	    !F_ISSET(session, WT_SESSION_CACHE_CURSORS))
		return (0);

	WT_ASSERT(session, !F_ISSET(cursor, WT_CURSTD_BULK | WT_CURSTD_CACHED));

	/*
	 * Do any sweeping first, if there are errors, it will
	 * be easier to clean up if the cursor is not already cached.
	 */
	if (--session->cursor_sweep_countdown == 0) {
		session->cursor_sweep_countdown =
		    WT_SESSION_CURSOR_SWEEP_COUNTDOWN;
		WT_RET(__wt_session_cursor_cache_sweep(session));
	}

	WT_ERR(cursor->cache(cursor));
	WT_STAT_CONN_INCR(session, cursor_cache);
	WT_STAT_DATA_INCR(session, cursor_cache);
	WT_ASSERT(session, F_ISSET(cursor, WT_CURSTD_CACHED));
	*released = true;

	if (0) {
		/*
		 * If caching fails, we must restore the state of the
		 * cursor back to open so that the close works from
		 * a known state. The reopen may also fail, but that
		 * doesn't matter at this point.
		 */
err:		WT_TRET(cursor->reopen(cursor, false));
		WT_ASSERT(session, !F_ISSET(cursor, WT_CURSTD_CACHED));
	}

	return (ret);
}

/*
 * __wt_cursor_cache_get --
 *	Open a matching cursor from the cache.
 */
int
__wt_cursor_cache_get(WT_SESSION_IMPL *session, const char *uri,
    WT_CURSOR *to_dup, const char *cfg[], WT_CURSOR **cursorp)
{
	WT_CONFIG_ITEM cval;
	WT_CURSOR *cursor;
	WT_CURSOR_BTREE *cbt;
	WT_DECL_RET;
	uint64_t bucket, hash_value;
	uint32_t overwrite_flag;
	bool have_config;

	if (!F_ISSET(session, WT_SESSION_CACHE_CURSORS))
		return (WT_NOTFOUND);

	/* If original config string is NULL or "", don't check it. */
	have_config = (cfg != NULL && cfg[0] != NULL && cfg[1] != NULL &&
	    (cfg[2] != NULL || cfg[1][0] != '\0'));

	/* Fast path overwrite configuration */
	if (have_config && cfg[2] == NULL &&
	    strcmp(cfg[1], "overwrite=false") == 0) {
		have_config = false;
		overwrite_flag = 0;
	} else
		overwrite_flag = WT_CURSTD_OVERWRITE;

	if (have_config) {
		/*
		 * Any cursors that have special configuration cannot
		 * be cached. There are some exceptions for configurations
		 * that only differ by a cursor flag, which we can patch
		 * up if we find a matching cursor.
		 */
		WT_RET(__wt_config_gets_def(session, cfg, "bulk", 0, &cval));
		if (cval.val)
			return (WT_NOTFOUND);

		WT_RET(__wt_config_gets_def(session, cfg, "dump", 0, &cval));
		if (cval.len != 0)
			return (WT_NOTFOUND);

		WT_RET(__wt_config_gets_def(
		    session, cfg, "next_random", 0, &cval));
		if (cval.val != 0)
			return (WT_NOTFOUND);

		WT_RET(__wt_config_gets_def(
		    session, cfg, "readonly", 0, &cval));
		if (cval.val)
			return (WT_NOTFOUND);

		/* Checkpoints are readonly, we won't cache them. */
		WT_RET(__wt_config_gets_def(
		    session, cfg, "checkpoint", 0, &cval));
		if (cval.val)
			return (WT_NOTFOUND);
	}

	/*
	 * Caller guarantees that exactly one of the URI and the
	 * duplicate cursor is non-NULL.
	 */
	if (to_dup != NULL) {
		WT_ASSERT(session, uri == NULL);
		uri = to_dup->uri;
		hash_value = to_dup->uri_hash;
	} else {
		WT_ASSERT(session, uri != NULL);
		hash_value = __wt_hash_city64(uri, strlen(uri));
	}

	/*
	 * Walk through all cursors, if there is a cached
	 * cursor that matches uri and configuration, use it.
	 */
	bucket = hash_value % WT_HASH_ARRAY_SIZE;
	TAILQ_FOREACH(cursor, &session->cursor_cache[bucket], q) {
		if (cursor->uri_hash == hash_value &&
		    strcmp(cursor->uri, uri) == 0) {
			if ((ret = cursor->reopen(cursor, false)) != 0) {
				F_CLR(cursor, WT_CURSTD_CACHEABLE);
				session->dhandle = NULL;
				(void)cursor->close(cursor);
				return (ret);
			}

			/*
			 * For these configuration values, there
			 * is no difference in the resulting
			 * cursor other than flag values, so fix
			 * them up according to the given configuration.
			 */
			F_CLR(cursor, WT_CURSTD_APPEND | WT_CURSTD_RAW |
			    WT_CURSTD_OVERWRITE);
			F_SET(cursor, overwrite_flag);
			/*
			 * If this is a btree cursor, clear its read_once flag.
			 */
			if (WT_PREFIX_MATCH(cursor->internal_uri, "file:")) {
				cbt = (WT_CURSOR_BTREE *)cursor;
				F_CLR(cbt, WT_CBT_READ_ONCE);
			} else {
				cbt = NULL;
			}

			if (have_config) {
				/*
				 * The append flag is only relevant to
				 * column stores.
				 */
				if (WT_CURSOR_RECNO(cursor)) {
					WT_RET(__wt_config_gets_def(
					    session, cfg, "append", 0, &cval));
					if (cval.val != 0)
						F_SET(cursor, WT_CURSTD_APPEND);
				}

				WT_RET(__wt_config_gets_def(
				    session, cfg, "overwrite", 1, &cval));
				if (cval.val == 0)
					F_CLR(cursor, WT_CURSTD_OVERWRITE);

				WT_RET(__wt_config_gets_def(
				    session, cfg, "raw", 0, &cval));
				if (cval.val != 0)
					F_SET(cursor, WT_CURSTD_RAW);

				if (cbt) {
					WT_RET(__wt_config_gets_def(
					    session,
					    cfg, "read_once", 0, &cval));
					if (cval.val != 0)
						F_SET(cbt, WT_CBT_READ_ONCE);
				}

			}

			WT_STAT_CONN_INCR(session, cursor_reopen);
			WT_STAT_DATA_INCR(session, cursor_reopen);

			*cursorp = cursor;
			return (0);
		}
	}
	return (WT_NOTFOUND);
}

/*
 * __wt_cursor_close --
 *	WT_CURSOR->close default implementation.
 */
void
__wt_cursor_close(WT_CURSOR *cursor)
{
	WT_SESSION_IMPL *session;

	session = (WT_SESSION_IMPL *)cursor->session;

	if (F_ISSET(cursor, WT_CURSTD_OPEN)) {
		TAILQ_REMOVE(&session->cursors, cursor, q);

		(void)__wt_atomic_sub32(&S2C(session)->open_cursor_count, 1);
		WT_STAT_DATA_DECR(session, cursor_open_count);
	}
	__wt_buf_free(session, &cursor->key);
	__wt_buf_free(session, &cursor->value);

	__wt_free(session, cursor->internal_uri);
	__wt_free(session, cursor->uri);
	__wt_overwrite_and_free(session, cursor);
}

/*
 * __wt_cursor_equals --
 *	WT_CURSOR->equals default implementation.
 */
int
__wt_cursor_equals(WT_CURSOR *cursor, WT_CURSOR *other, int *equalp)
{
	WT_DECL_RET;
	WT_SESSION_IMPL *session;
	int cmp;

	CURSOR_API_CALL(cursor, session, equals, NULL);

	WT_ERR(cursor->compare(cursor, other, &cmp));
	*equalp = (cmp == 0) ? 1 : 0;

err:	API_END_RET(session, ret);
}

/*
 * __cursor_modify --
 *	WT_CURSOR->modify default implementation.
 */
static int
__cursor_modify(WT_CURSOR *cursor, WT_MODIFY *entries, int nentries)
{
	WT_DECL_RET;
	WT_SESSION_IMPL *session;

	CURSOR_API_CALL(cursor, session, modify, NULL);

	WT_STAT_CONN_INCR(session, cursor_modify);
	WT_STAT_DATA_INCR(session, cursor_modify);

	/* Check for a rational modify vector count. */
	if (nentries <= 0)
		WT_ERR_MSG(session, EINVAL,
		    "Illegal modify vector with %d entries", nentries);

	/*
	 * The underlying btree code cannot support WT_CURSOR.modify within
	 * a read-uncommitted transaction. Disallow it here for consistency.
	 */
	if (session->txn.isolation == WT_ISO_READ_UNCOMMITTED)
		WT_ERR_MSG(session, ENOTSUP,
		    "not supported in read-uncommitted transactions");

	WT_ERR(__cursor_checkkey(cursor));

	/* Get the current value, apply the modifications. */
	WT_ERR(cursor->search(cursor));
	WT_ERR(__wt_modify_apply_api(session, cursor, entries, nentries));

	/* We know both key and value are set, "overwrite" doesn't matter. */
	ret = cursor->update(cursor);

err:	API_END_RET(session, ret);
}

/*
 * __wt_cursor_reconfigure --
 *	Set runtime-configurable settings.
 */
int
__wt_cursor_reconfigure(WT_CURSOR *cursor, const char *config)
{
	WT_CONFIG_ITEM cval;
	WT_DECL_RET;
	WT_SESSION_IMPL *session;

	CURSOR_API_CALL(cursor, session, reconfigure, NULL);

	/* Reconfiguration resets the cursor. */
	WT_ERR(cursor->reset(cursor));

	/*
	 * append
	 * Only relevant to column stores.
	 */
	if (WT_CURSOR_RECNO(cursor)) {
		if ((ret = __wt_config_getones(
		    session, config, "append", &cval)) == 0) {
			if (cval.val)
				F_SET(cursor, WT_CURSTD_APPEND);
			else
				F_CLR(cursor, WT_CURSTD_APPEND);
		} else
			WT_ERR_NOTFOUND_OK(ret);
	}

	/*
	 * overwrite
	 */
	if ((ret = __wt_config_getones(
	    session, config, "overwrite", &cval)) == 0) {
		if (cval.val)
			F_SET(cursor, WT_CURSTD_OVERWRITE);
		else
			F_CLR(cursor, WT_CURSTD_OVERWRITE);
	} else
		WT_ERR_NOTFOUND_OK(ret);

err:	API_END_RET(session, ret);
}

/*
 * __wt_cursor_dup_position --
 *	Set a cursor to another cursor's position.
 */
int
__wt_cursor_dup_position(WT_CURSOR *to_dup, WT_CURSOR *cursor)
{
	WT_DECL_RET;
	WT_ITEM key;

	/*
	 * Get a copy of the cursor's raw key, and set it in the new cursor,
	 * then search for that key to position the cursor.
	 *
	 * We don't clear the WT_ITEM structure: all that happens when getting
	 * and setting the key is the data/size fields are reset to reference
	 * the original cursor's key.
	 *
	 * That said, we're playing games with the cursor flags: setting the key
	 * sets the key/value application-set flags in the new cursor, which may
	 * or may not be correct, but there's nothing simple that fixes it.  We
	 * depend on the subsequent cursor search to clean things up, as search
	 * is required to copy and/or reference private memory after success.
	 */
	WT_RET(__wt_cursor_get_raw_key(to_dup, &key));
	__wt_cursor_set_raw_key(cursor, &key);

	/*
	 * We now have a reference to the raw key, but we don't know anything
	 * about the memory in which it's stored, it could be btree/file page
	 * memory in the cache, application memory or the original cursor's
	 * key/value WT_ITEMs.  Memory allocated in support of another cursor
	 * could be discarded when that cursor is closed, so it's a problem.
	 * However, doing a search to position the cursor will fix the problem:
	 * cursors cannot reference application memory after cursor operations
	 * and that requirement will save the day.
	 */
	F_SET(cursor, WT_CURSTD_RAW_SEARCH);
	ret = cursor->search(cursor);
	F_CLR(cursor, WT_CURSTD_RAW_SEARCH);

	return (ret);
}

/*
 * __wt_cursor_init --
 *	Default cursor initialization.
 */
int
__wt_cursor_init(WT_CURSOR *cursor,
    const char *uri, WT_CURSOR *owner, const char *cfg[], WT_CURSOR **cursorp)
{
	WT_CONFIG_ITEM cval;
	WT_CURSOR *cdump;
	WT_SESSION_IMPL *session;
	bool readonly;

	session = (WT_SESSION_IMPL *)cursor->session;

	if (cursor->internal_uri == NULL)
		WT_RET(__wt_strdup(session, uri, &cursor->internal_uri));

	/*
	 * append
	 * The append flag is only relevant to column stores.
	 */
	if (WT_CURSOR_RECNO(cursor)) {
		WT_RET(__wt_config_gets_def(session, cfg, "append", 0, &cval));
		if (cval.val != 0)
			F_SET(cursor, WT_CURSTD_APPEND);
	}

	/*
	 * checkpoint, readonly
	 * Checkpoint cursors are permanently read-only, avoid the extra work
	 * of two configuration string checks.
	 */
	readonly = F_ISSET(S2C(session), WT_CONN_READONLY);
	if (!readonly) {
		WT_RET(
		    __wt_config_gets_def(session, cfg, "checkpoint", 0, &cval));
		readonly = cval.len != 0;
	}
	if (!readonly) {
		WT_RET(
		    __wt_config_gets_def(session, cfg, "readonly", 0, &cval));
		readonly = cval.val != 0;
	}
	if (readonly) {
		cursor->insert = __wt_cursor_notsup;
		cursor->modify = __wt_cursor_modify_notsup;
		cursor->remove = __wt_cursor_notsup;
		cursor->reserve = __wt_cursor_notsup;
		cursor->update = __wt_cursor_notsup;
		F_CLR(cursor, WT_CURSTD_CACHEABLE);
	}

	/*
	 * dump
	 * If an index cursor is opened with dump, then this
	 * function is called on the index files, with the dump
	 * config string, and with the index cursor as an owner.
	 * We don't want to create a dump cursor in that case, because
	 * we'll create the dump cursor on the index cursor itself.
	 */
	WT_RET(__wt_config_gets_def(session, cfg, "dump", 0, &cval));
	if (cval.len != 0 && owner == NULL) {
		F_SET(cursor,
		    WT_STRING_MATCH("json", cval.str, cval.len) ?
		    WT_CURSTD_DUMP_JSON :
		    (WT_STRING_MATCH("print", cval.str, cval.len) ?
		    WT_CURSTD_DUMP_PRINT : WT_CURSTD_DUMP_HEX));
		/*
		 * Dump cursors should not have owners: only the
		 * top-level cursor should be wrapped in a dump cursor.
		 */
		WT_RET(__wt_curdump_create(cursor, owner, &cdump));
		owner = cdump;
		F_CLR(cursor, WT_CURSTD_CACHEABLE);
	} else
		cdump = NULL;

	/* overwrite */
	WT_RET(__wt_config_gets_def(session, cfg, "overwrite", 1, &cval));
	if (cval.val)
		F_SET(cursor, WT_CURSTD_OVERWRITE);
	else
		F_CLR(cursor, WT_CURSTD_OVERWRITE);

	/* raw */
	WT_RET(__wt_config_gets_def(session, cfg, "raw", 0, &cval));
	if (cval.val != 0)
		F_SET(cursor, WT_CURSTD_RAW);

	/*
	 * WT_CURSOR.modify supported on 'S' and 'u' value formats, but may have
	 * been already initialized (file cursors have a faster implementation).
	 */
	if ((WT_STREQ(cursor->value_format, "S") ||
	    WT_STREQ(cursor->value_format, "u")) &&
	    cursor->modify == __wt_cursor_modify_notsup)
		cursor->modify = __cursor_modify;

	/*
	 * Cursors that are internal to some other cursor (such as file cursors
	 * inside a table cursor) should be closed after the containing cursor.
	 * Arrange for that to happen by putting internal cursors after their
	 * owners on the queue.
	 */
	if (owner != NULL) {
		WT_ASSERT(session, F_ISSET(owner, WT_CURSTD_OPEN));
		TAILQ_INSERT_AFTER(&session->cursors, owner, cursor, q);
	} else
		TAILQ_INSERT_HEAD(&session->cursors, cursor, q);

	F_SET(cursor, WT_CURSTD_OPEN);
	(void)__wt_atomic_add32(&S2C(session)->open_cursor_count, 1);
	WT_STAT_DATA_INCR(session, cursor_open_count);

	*cursorp = (cdump != NULL) ? cdump : cursor;
	return (0);
}