From 5e02e7fb562afd42d112253e2c88d326874d93df Mon Sep 17 00:00:00 2001
From: Leonid Yuriev <leo@yuriev.ru>
Date: Tue, 17 Nov 2020 08:01:08 +0300
Subject: [PATCH] mdbx: add `MDBX_SET_LOWERBOUND` for `mdbx_cursor_get()`.

Change-Id: I3638fdd10be8dfe128c43b465e9ca71f89175b3e
---
 mdbx.h     | 15 ++++++++++++++-
 src/core.c | 27 +++++++++++++++++++++++++++
 2 files changed, 41 insertions(+), 1 deletion(-)

diff --git a/mdbx.h b/mdbx.h
index 79a6ba7c..1d4ad575 100644
--- a/mdbx.h
+++ b/mdbx.h
@@ -1505,7 +1505,20 @@ enum MDBX_cursor_op {
 
   /** \ref MDBX_DUPFIXED -only: Position at previous page and return up to
    * a page of duplicate data items. */
-  MDBX_PREV_MULTIPLE
+  MDBX_PREV_MULTIPLE,
+
+  /** Position at first key-value pair greater than or equal to specified,
+   * return both key and data, and the return code depends on a exact match.
+   *
+   * For non DUPSORT-ed collections this work the same to \ref MDBX_SET_RANGE,
+   * but returns \ref MDBX_SUCCESS if key found exactly and
+   * \ref MDBX_RESULT_TRUE if greater key was found.
+   *
+   * For DUPSORT-ed a data value is taken into account for duplicates,
+   * i.e. for a pairs/tuples of a key and an each data value of duplicates.
+   * Returns \ref MDBX_SUCCESS if key-value pair found exactly and
+   * \ref MDBX_RESULT_TRUE if the next pair was returned. */
+  MDBX_SET_LOWERBOUND
 };
 #ifndef __cplusplus
 /** \ingroup c_cursors */
diff --git a/src/core.c b/src/core.c
index 4148ae73..8404c537 100644
--- a/src/core.c
+++ b/src/core.c
@@ -12575,6 +12575,33 @@ int mdbx_cursor_get(MDBX_cursor *mc, MDBX_val *key, MDBX_val *data,
   case MDBX_LAST_DUP:
     mfunc = mdbx_cursor_last;
     goto mmove;
+  case MDBX_SET_LOWERBOUND: {
+    if (unlikely(key == NULL || data == NULL))
+      return MDBX_EINVAL;
+    MDBX_val save_data = *data;
+    rc = mdbx_cursor_set(mc, key, data, MDBX_SET_RANGE, &exact);
+    if (rc == MDBX_SUCCESS && exact && mc->mc_xcursor) {
+      mc->mc_flags &= ~C_DEL;
+      if (mc->mc_xcursor->mx_cursor.mc_flags & C_INITIALIZED) {
+        *data = save_data;
+        exact = 0;
+        rc = mdbx_cursor_set(&mc->mc_xcursor->mx_cursor, data, NULL,
+                             MDBX_SET_RANGE, &exact);
+        if (rc == MDBX_NOTFOUND) {
+          mdbx_cassert(mc, !exact);
+          rc = mdbx_cursor_next(mc, key, data, MDBX_NEXT_NODUP);
+        }
+      } else {
+        int cmp = mc->mc_dbx->md_dcmp(&save_data, data);
+        exact = (cmp == 0);
+        if (cmp > 0)
+          rc = mdbx_cursor_next(mc, key, data, MDBX_NEXT_NODUP);
+      }
+    }
+    if (rc == MDBX_SUCCESS && !exact)
+      rc = MDBX_RESULT_TRUE;
+    break;
+  }
   default:
     mdbx_debug("unhandled/unimplemented cursor operation %u", op);
     return MDBX_EINVAL;